JP2003181609A - Method and apparatus for estimating and controlling flow pattern of molten steel in continuous casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for controlling a flow pattern of molten steel in continuous casting which can improve and stabilize the quality of a cast strip prepared by continuous casting, particularly can improve and stabilize the quality of a cast strip by preventing mold powder inclusion derived from a molten steel flow pattern within a mold. <P>SOLUTION: This method includes the steps of: (a) continuously casting molten steel delivered from an immersion nozzle; (b) measuring the temperature of a long-side copper plate in its plurality of points in the mold in a long-side width direction in the mold; (c) detecting a flow pattern of the molten steel within the mold based on a change in copper plate temperature in each measuring point with the elapse of time; and (d) controlling the flow pattern based on the results of detection so as to provide a predetermined flow pattern. The temperature of the copper plate of the mold is measured with a plurality of temperature measuring elements buried in the backside of the copper plate of the mold for continuous casting. The temperature measuring elements are provided in a position 10 to 135 mm away in a strip drawing direction from the position of the surface of the molten steel within the mold. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a continuous casting method for steel. In particular, it relates to a method for estimating and controlling the flow pattern of molten steel in continuous casting, and an apparatus therefor.

[0002]

2. Description of the Related Art In continuous casting of steel, molten steel is discharged into a mold at a high speed through a dipping nozzle, so that this discharge flow causes a molten steel flow in the mold, and this molten steel flow is It has a great influence on the surface and internal properties of the slab. For example, when the surface velocity of the molten metal in the mold (hereinafter referred to as “meniscus”) is too fast, or when vertical vortices are generated in the meniscus, the mold powder is caught in the molten steel. It is also known that the floating separation of deoxidized products such as Al ₂ O _{3 in} molten steel is also influenced by the molten steel flow, and mold powder and deoxidized products caught in the slab are It becomes a defect of non-metallic inclusion properties.

The molten steel flow in the mold has the same casting conditions.
Even inside the immersion nozzle ₂O₃Adhesion, immersion
Casting due to melting loss of the shell, opening of the sliding nozzle, etc.
Change in. Therefore, molten steel flow was detected and detected
By controlling the strength and direction of the applied magnetic field from the molten steel flow condition
Controlling the flow of molten steel in the mold is an important factor in improving the quality of the slab.
Many have been proposed as important issues.

For example, in Japanese Unexamined Patent Publication No. 62-252650 (hereinafter referred to as "Prior Art 1"), the difference in molten steel level between the left and right of the immersion nozzle is detected by a thermocouple embedded in a copper plate on the short side of the mold, and the level difference is detected. There is disclosed a molten steel flow control method in which the stirring direction and stirring thrust of an electromagnetic stirring device are controlled so as to eliminate the above.

JP-A-3-275256 (hereinafter, referred to as
In the description of "prior art 2"), the temperature distribution of the copper plate on the long side of the mold is measured by a thermocouple embedded in the copper plate on the long side of the mold, and the occurrence of molten steel drift is detected from the temperature distribution on the left and right sides of the mold. There is disclosed a method of controlling the drift of molten steel in a mold by individually controlling the currents supplied to two DC electromagnet type electromagnetic brake devices arranged on the back surface of the long side of the mold according to the generation direction and the degree of occurrence. .

Japanese Unexamined Patent Publication No. 4-284956 (hereinafter,
In "Prior Art 3"), two non-contact distance meters are provided on the meniscus between the dipping nozzle and the short side of the mold to measure the fluctuation of the meniscus surface. A method has been disclosed in which the propagation velocity of surface waves is obtained from a cross-correlation function and the discharge flow velocity from the immersion nozzle is controlled by an electromagnetic stirrer so that this propagation velocity is below a predetermined value.

[0007]

In Prior Art 1 and Prior Art 2, molten steel flow is detected from the distribution of the temperature of the mold copper plate,
Flow control is performed based on the detected molten steel flow.However, the change in the mold copper plate temperature distribution does not only occur due to the change in the molten steel flow condition, but also the contact state between the mold and the solidification shell and the inflow of mold powder. It also occurs due to changes in the status. As described above, since there is a change in the mold copper plate temperature distribution due to factors other than the molten steel flow, the molten steel flow cannot be accurately detected in Prior Art 1 and Prior Art 2 in which the molten steel flow is simply detected from the mold copper plate temperature distribution.

Further, as will be described in detail later, from the results of the investigation conducted by the present inventors, in order to reduce the mold powder and the deoxidized product, it is necessary to prevent a non-uniform flow in the mold to form a symmetrical flow. Insufficient and it was confirmed that within some symmetric flows there was an optimal flow pattern.

The prior art 3 is an effective means for controlling the flow, but it controls only the molten steel flow velocity of the meniscus and is insufficient for detecting the molten steel flow pattern of the mold. Similarly, the flow patterns cannot be detected in Prior Art 1 and Prior Art 2.

The object of the present invention is to improve and stabilize the quality of the slabs produced in continuous casting, especially by preventing the entrainment of mold powder caused by the molten steel flow pattern in the mold. It is intended to stabilize and supply good slab to the lower step. Therefore, the present invention provides a molten steel flow pattern control method capable of maintaining an optimum flow pattern in continuous casting, and further, a temperature measuring device of a mold copper plate for accurately estimating the molten steel flow condition and this temperature. Provided is a method for estimating the flow state of molten steel in a mold using a measuring device.

[0011]

To achieve the above object, firstly, the present invention provides a method for estimating a molten steel flow pattern in continuous casting, which comprises the following steps.

A step of continuously casting the molten steel discharged from the immersion nozzle into the mold; a step of measuring the mold copper plate temperature in the width direction of the mold with a temperature measuring device for the mold copper plate; The process of estimating the flow pattern of molten steel in the mold from the distribution.

The above method for estimating the flow pattern of molten steel is such that the detected flow pattern becomes a predetermined pattern.
It is preferable to have a step of applying a magnetic field to the molten steel discharged into the mold. The applied magnetic field is preferably a moving magnetic field that moves in the horizontal direction.

Further, the method for estimating the flow pattern of molten steel preferably has the following steps: Mold copper plate temperature measured by a temperature measuring device for mold copper plate temperature, thickness of mold copper plate, molten steel of mold copper plate Cooling the molten steel in the mold from the molten steel in the mold using the distance from the side surface to the tip of the temperature measuring element, the cooling water temperature for the copper plate in the mold, the solidification shell thickness, the thickness of the mold powder layer, and the molten steel temperature in the mold. A step of obtaining a heat flux to water; a step of obtaining a convection heat transfer coefficient between the molten steel and the solidification shell corresponding to the heat flux; and a step of obtaining a flow velocity of the molten steel along the solidification shell from the convection heat transfer coefficient.

The above flow pattern estimating method may further include a step of correcting the temperature of the copper plate on the long side of the mold at each measurement point: the surface of the solidified shell in the width direction of the slab below the lower end of the mold. The shape is measured; the heat transfer resistance between the copper plate on the long side of the mold and the solidified shell is estimated from the measured surface shape; the temperature of the copper plate on the long side of the mold at each measurement point is corrected by the estimated heat transfer resistance.

The temperature measuring device for the mold copper plate temperature in the above flow pattern estimating method preferably comprises a plurality of temperature measuring elements embedded in the back surface of the mold copper plate for continuous casting. The temperature measuring element is preferably in the range of 10 to 135 mm away from the molten steel molten metal surface position in the mold in the slab drawing direction, and the distance from the molten steel side surface of the mold copper plate to the temperature measuring element tip is 16 mm or less, and, It is installed over a range corresponding to the entire width of the slab, with the installation interval in the mold width direction being 200 mm or less.

The step of estimating the above-mentioned flow pattern is preferably performed by one selected from the following: (A) The measurement point at which the temperature of the copper plate on the long side of the mold rises from the change with time of the temperature of the copper plate on the long side of the mold. The distribution is determined and the flow pattern of molten steel in the mold is estimated based on the distribution of the rising measurement points. (B) The distribution of the measurement points at which the temperature of the copper plate on the long side of the mold is lowered is obtained from the change in the temperature of the copper plate on the long side of the mold, and the flow pattern of the molten steel in the mold is estimated based on the distribution of the measured points of the measurement. (C) From the time-dependent change of the copper plate temperature on the long side of the mold, the distribution of the measurement points at which the copper plate temperature at the long side of the mold rises and the distribution of the measurement points at which the copper plate temperature descends are obtained, and the mold is based on the distribution of the measurement points that rise and the distribution of the measurement points that descend. Estimate the flow pattern of inner molten steel. (D) The flow pattern of the molten steel in the mold is estimated by the number of peaks and the positions of the peaks of the mold copper plate temperature in the mold width direction. (E) The drift of molten steel in the mold is estimated by comparing the maximum value of the mold copper plate temperature and the position of the maximum value on the left and right of the mold width direction with reference to the center position in the mold width direction based on the measured temperature.

Secondly, the present invention provides a temperature measuring device for a mold copper plate, which comprises: a plurality of temperature measuring elements embedded in the back surface of the mold copper plate for continuous casting; Within the range of 10 to 135 mm away from the position in the slab withdrawal direction, the distance from the molten steel side surface of the mold copper plate to the tip of the temperature measuring element is 16 mm or less, and the installation interval in the mold width direction is 200 mm or less to the full width of the slab. It is installed over a corresponding range.

In the above temperature measuring device, the temperature measuring element is installed so as to penetrate through the pipe sealed with the cooling water in the water box, and the seal packing is provided around the temperature measuring element. Is preferred.

Thirdly, the present invention provides a method for determining surface defects of continuously cast slabs, which comprises: a width direction of the back surface of a copper mold plate in the range of 10 to 135 mm away from the meniscus position in the mold in the slab drawing direction. A plurality of temperature measuring elements are arranged in
The widthwise distribution of the mold copper plate temperature is measured; the surface defects of the slab are determined based on the mold widthwise temperature distribution.

The determination of the above-mentioned surface defect is performed by one of the following. (A) The surface defect of the cast piece is determined based on the maximum value of the temperature distribution in the mold width direction. (B) The surface defect of the slab is judged based on the minimum value of the temperature distribution in the mold width direction. (C) The surface defect of the slab is determined based on the average value of the temperature distribution in the mold width direction. (D) The surface defect of the cast piece is determined based on the difference between the average value of the mold width direction temperature distribution and the typical value of the typical mold width direction temperature distribution at the cast piece drawing speed. (E) With the immersion nozzle arranged in the center of the mold as the center,
Of the value obtained by subtracting the minimum value from the maximum value of the temperature distribution on the left side of the mold width direction, and the value obtained by subtracting the minimum value from the maximum value of the temperature distribution on the right side of the mold width direction, of the slab based on the larger value. Determine surface defects. (F) With the immersion nozzle arranged in the center of the mold as the center,
The surface defect of the slab is determined based on the absolute value of the difference between the maximum value of the temperature distribution on the left side of the mold width direction and the maximum value of the temperature distribution on the right side of the mold width direction. (G) The surface defect of the slab is determined based on the maximum value of the temperature fluctuation amount per unit time among the temperature measurement values obtained by the temperature measuring elements.

Fourthly, the present invention provides a molten steel flow detection method in continuous casting comprising: a plurality of temperature measuring elements arranged on the rear surface of a continuous casting mold copper plate in a direction orthogonal to the slab drawing direction. The temperature of the mold copper plate is measured by these plural temperature measuring elements; when the spatial frequency f of the molten steel flow is defined by f = 1 / L using the fluctuation wavelength L (mm) of the molten steel flow,
Cutoff spatial frequency of each measured copper mold plate is 2
/ Lower-pass filter treatment as a range larger than [mold width W] and smaller than 0.01; the molten steel flow state in the mold is estimated based on the temperature distribution of the mold copper plate temperature subjected to the low-pass filter.

In the above molten steel flow detecting method, the distance between the adjacent temperature measuring elements is wider than 44.3 / 3 mm, and 0.4
It is preferably adjusted to a range narrower than 43 × [mold width W] / 6 mm. Furthermore, in the above molten steel flow detection method, it is preferable to perform low-pass filter processing using a data series in which measurement data is folded back and expanded at the end points of the mold width on both sides.

Fifthly, the present invention provides a molten steel flow detection method in continuous casting, which comprises the following: The distance between adjacent temperature measuring elements on the rear surface of the continuous casting mold copper plate in the direction orthogonal to the slab drawing direction. 44.3 / 3 mm to 0.443 ×
[Mold width W] / 6 mm with a plurality of temperature measuring elements arranged;
The temperature of the mold copper plate is measured by these plural temperature measuring elements; the measured temperature of each mold copper plate is spatially moving averaged; the molten steel flow state in the mold is estimated based on the temperature distribution of the space moving averaged mold copper plate temperature .

Sixth, the present invention provides a method for evaluating the non-uniformity of heat removal in a mold in continuous casting, which comprises: A temperature measuring element is arranged; the temperature of the mold copper plate is measured by the plurality of temperature measuring elements; the measured temperature of each mold copper plate is low-pass filtered; The nonuniformity of heat removal in the mold is evaluated based on the difference.

Seventh, the present invention provides a method for detecting molten steel flow in continuous casting, which comprises: arranging a plurality of temperature measuring elements on the back surface of a copper plate for continuous casting in a direction orthogonal to the slab drawing direction; The mold copper plate temperature is measured by these plural temperature measuring elements; each measured mold copper plate temperature is sampled at intervals of 60 seconds or less; the molten steel flow condition in the mold is estimated based on the mold copper plate temperature sampled at this interval. To do.

Eighth, the present invention provides a molten steel flow control method in continuous casting comprising: a long side of a mold for continuous casting, and a plurality of temperature measuring elements arranged in the width direction of the back surface of the copper plate to obtain a long side of the mold. The temperature distribution in the width direction of the copper plate is measured; the magnetic field strength of the magnetic field generator attached to the mold, the slab withdrawing speed, and the dipping so that the difference between the maximum value and the minimum value of the measured temperature distribution is 12 ° C or less. Nozzle immersion depth, A into immersion nozzle
Any one or two or more of the r blowing amount is adjusted.

In the above molten steel flow control method, the magnetic field strength of the magnetic field generator attached to the mold, the slab drawing speed,
Any one or two or more of the immersion depth of the immersion nozzle and the amount of Ar blown into the immersion nozzle, the difference between the maximum value and the minimum value of the measured temperature distribution is 12 ° C. or less, and It is preferable to adjust the temperature difference at the symmetrical positions on the left and right sides of the copper plate in the long side of the mold centering on the immersion nozzle to be 10 ° C. or less. In the above molten steel flow control method, it is preferable that the magnetic field strength of the magnetic field generator attached to the mold is adjusted independently on the left and right in the mold width direction with the immersion nozzle as a boundary.

Ninth, the present invention provides a molten steel flow control method in continuous casting, which comprises: a long side of a mold for continuous casting; Measure the temperature at each position in the width direction of the copper plate; calculate the molten steel flow velocity at each measurement point based on this temperature measurement value to obtain the molten steel flow velocity distribution in the copper plate width direction on the long side of the mold; The magnetic field strength of the magnetic field generator attached to the mold so that the difference from the minimum value is 0.25 m / sec or less,
Any one or two or more of the slab withdrawal speed, the immersion depth of the immersion nozzle, and the amount of Ar blown into the immersion nozzle are adjusted.

In the above molten steel flow control method, the magnetic field strength of the magnetic field generator attached to the mold, the slab drawing speed,
When the difference between the maximum value and the minimum value of the obtained molten steel flow velocity distribution is 0.25 m / sec or less for any one or two or more of the immersion depth of the immersion nozzle and the amount of Ar blown into the immersion nozzle. In addition, the difference in molten steel flow velocity at the symmetrical positions on the left and right sides of the copper plate in the long side of the mold centering on the immersion nozzle is 0.20 m / s.
It is desirable to adjust so that it becomes ec or less.

In the above molten steel flow control method, it is preferable that the magnetic field strength of the magnetic field generator attached to the mold is adjusted independently on the left and right sides of the mold in the width direction of the mold.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Best Mode 1 (Method for Controlling Molten Steel Flow Pattern) The flow pattern of molten steel in a mold is such that Ar bubbles floating in the mold and an applied magnetic field even if the flow pattern is symmetrical and has no drift. Changes intricately due to. When the flow pattern is simplified, it can be roughly classified into three patterns, that is, pattern A to pattern C shown in FIG. In FIG. 1, 3 is the short side of the mold, 4 is molten steel, 5 is a solidification shell, 8 is a dipping nozzle,
Reference numeral 9 is a discharge hole, 10 is a discharge flow, 13 is a meniscus, and 14 is a mold powder.

In the pattern A, the discharge flow 10 from the immersion nozzle 8 reaches the solidification shell 5 on the short side 3 of the mold.
After the collision, the flow is separated into two streams, and one stream rises up to the meniscus 13 along the solidification shell 5 on the short side 3 of the mold, and further the meniscus 13 is moved from the short side 3 of the mold to the center side of the mold (the dipping nozzle). 8), and the other one is a flow pattern in which the flow descends from the point of collision with the solidified shell 5 to the lower side of the mold.

On the other hand, in the pattern B, the discharge flow 10 from the immersion nozzle 8 reaches the solidification shell 5 on the short side 3 of the mold due to the floating of Ar bubbles on the discharge flow 10 or the effect of the magnetic field application. Instead, the particles are dispersed from the discharge hole 9 to the solidified shell 5 on the short side 3 of the mold to form an upflow and a downflow, and at the meniscus 13, the dipping nozzle 8 and the short side 3 of the mold are intermediate. The flow pattern is such that, with the vicinity of the position as a boundary, the flow is toward the mold center side (immersion nozzle 8 side) on the immersion nozzle 8 side and is opposite to the mold short side 3 on the mold short side 3 side. The pattern C is a flow pattern in which an upward flow of the discharge flow 10 exists near the immersion nozzle 8, and appears mainly due to the floating of coarse Ar bubbles or the effect of magnetic field application. In pattern C, in the meniscus 13,
The main flow is from the mold center side (immersion nozzle 8 side) toward the mold short side 3 side.

The amount of product defects due to mold powder defects in thin steel sheet products was investigated for each flow pattern of molten steel in the mold. Figure 2 shows the survey results. As shown in FIG. 2, the flow pattern of the molten steel in the mold is the pattern B.
In the case of No. 1, there were few mold powder defects, and it was found that the slab quality was the best. The reason for this is considered as follows.

In the case of pattern A, a vortex that causes mixing of mold powder into the molten steel is apt to occur in the meniscus between the center of the mold and a position 1/4 of the mold width away from the center of the mold, and This is because the mold powder is scraped off by the surface flow of molten steel when the surface flow velocity is high, and mixing of the mold powder due to this cause is likely to occur.
In the case of pattern C, the upward flow of molten steel near the immersion nozzle and the floating coarse Ar bubbles cause fluctuations and disturbance of the meniscus, mixing of mold powder occurs, and the surface velocity of molten steel is high. This is because vertical vortices are generated in the vicinity of the short side of the mold, which causes mixing of mold powder. On the other hand, in the case of the pattern B, there is no generation of vortices in the meniscus and the appearance of strong surface flow,
This is because the flow conditions are such that entrapment of mold powder is unlikely to occur.

As described above, by setting the flow pattern of the molten steel in the mold to be the pattern B, it is possible to prevent the deterioration of the quality of the slab, reduce the rate of product downgrade, and improve the rate of maintenance of the slab. . However, as described above, even if the casting conditions are the same, the flow pattern of the molten steel in the mold changes during casting. If the flow pattern can be detected during casting, if the flow pattern deviates from the predetermined flow pattern, the strength of the applied magnetic field can be changed to restore the predetermined flow pattern.

The present inventors have found that the flow pattern of molten steel in the mold can be detected by measuring the temperature of the copper plate on the long side of the mold. That is, the mold long side copper plate temperature in the vicinity of the meniscus of the mold, the mold long side copper plate temperature becomes high at a position corresponding to the rising flow of molten steel, and the mold long side copper plate temperature is high at a position corresponding to the change in the flow pattern. Changes. For example, in the case of the pattern A, an ascending flow is formed near the short side of the mold, so the temperature of the copper plate on the long side of the mold near the short side of the mold becomes high. This is because the discharge flow has a higher temperature than the molten steel in the mold,
This is because, at the position where the discharge flow rises, the temperature of the molten steel rises and the heat transfer is promoted by the flow of the molten steel, the amount of heat transferred to the copper plate on the long side of the mold increases, and the temperature of the copper plate on the long side of the mold rises. However, the temperature of the copper plate on the long side of the mold does not change only by the effect of molten steel flow, but also changes by the contact state between the mold and the solidified shell, the inflow state of mold powder, and the like. Therefore, if the molten steel flow is simply detected from the distribution of the absolute value of the copper plate temperature on the long side of the mold in the width direction of the slab, it may be erroneously detected. That is, an accurate flow pattern cannot be detected unless the influence of the factors other than the molten steel flow on the temperature of the copper plate on the long side of the mold is removed. The present inventors, the change over time of the temperature at each measurement point to measure the copper plate temperature of the long side of the mold, that is, by using the rate of temperature rise and fall for each time as an index, factors other than molten steel flow It was found that the influence on the copper plate temperature on the long side of the mold can be minimized and an accurate flow pattern can be detected. This is because the temperature change of the copper plate on the long side of the mold due to factors other than the molten steel flow occurs relatively slowly. At that time, the distribution of the measurement points where the mold long side copper plate temperature rises and the measurement points where the temperature rises is obtained, and if the flow pattern is detected based on the distribution of the measurement points that rise and / or the distribution of the measurement points that descend, It turns out that it can be detected accurately. This is because the copper plate temperature on the long side of the mold changes with a distribution when the flow pattern changes.

The surface shape of the solidified shell in the width direction of the slab is measured below the lower end of the mold, and the heat transfer resistance between the copper plate on the long side of the mold and the solidified shell is estimated from the surface shape of the solidified shell. If the temperature of the copper plate on the long side of the mold at each measurement point is corrected by the heat transfer resistance, the effect on the temperature of the copper plate on the long side of the mold due to the contact state between the mold and the solidification shell can be reduced, and the flow pattern can be detected more accurately. it can. In this case, since the surface shape of the solidified shell measured below the lower end of the mold is fed back to the measured value of the mold long side copper plate temperature in the vicinity of the meniscus, the surface shape data of the solidified shell to be fed back is from the vicinity of the meniscus in the solidified shell. It is accompanied by a time lag before reaching the surface shape measurement position. However, even if the surface shape measurement position is 1.5 m below the meniscus, the slab drawing speed is 1.8 m /
If it is min, the required time is about 50 seconds. In the flow control of the molten steel in the mold, control at short time intervals, for example, when the applied magnetic field is changed, it tends to diverge, and therefore control at a somewhat long cycle is suitable. Therefore, such a time difference does not pose a problem and flow control can be sufficiently performed.

As the magnetic field applied to the discharge flow, it is preferable to use a moving magnetic field in which the magnetic field moves in the horizontal direction. In the moving magnetic field, by selecting and applying an appropriate magnetic field strength,
This is because the molten steel flow velocity and flow pattern can be freely controlled as compared with the static magnetic field generated by a direct current.

The present invention will be described with reference to the drawings. FIG. 3 is a schematic front cross-sectional view of a continuous casting machine mold part showing one embodiment of the present invention, and FIG. 4 is a schematic side cross-sectional view. In FIG. 3 and FIG. 4, a tundish 6 is arranged above a mold 1 composed of opposed mold long sides 2 and opposed mold short sides 3 installed in the mold long sides 2. There is. At the bottom of the tundish 6, a fixed plate 22 and a sliding plate 2 are provided.
3 and a sliding nozzle 7 composed of a rectifying nozzle 24, and further, a dipping nozzle 8 is arranged on the lower surface side of the sliding nozzle 7 to form a molten steel outflow hole 28 from the tundish 6 to the mold 1. The molten steel 4 injected into the tundish 6 from a ladle (not shown) is provided under the immersion nozzle 8 via the molten steel outflow hole 28,
Moreover, a discharge flow 10 is injected into the mold 1 toward the mold short side 3 from the discharge hole 9 immersed in the molten steel 4 in the mold 1. Then, the molten steel 4 is cooled in the mold 1 to form a solidified shell 5, which is drawn below the mold 1 to form a slab.

A porous brick 25 is fitted into the molten steel outflow hole 28 of the fixed plate 22, and the molten steel outflow hole 28 is provided.
In order to prevent Al ₂ O _{3 from} adhering to the wall surface of Ar, Ar is blown from the porous brick 25 into the molten steel outflow hole 28.
The blown Ar flows into the mold 1 together with the molten steel 4 through the immersion nozzle 8 and the discharge hole 9, and the molten steel 4 in the mold 1
And floats on the meniscus 13 and penetrates the mold powder 14 added on the meniscus 13 to reach the atmosphere.

On the back surface of the long side 2 of the mold, there are a magnetic field generator 11 and a magnetic field generator 12 which are divided into two parts on the left and right in the width direction of the long side 2 of the mold with the immersion nozzle 8 as a boundary.
The center positions of the casting directions 1 and 12 in the casting direction are set as a range between the lower end position of the discharge hole 9 and the lower end position of the mold 1 and are arranged so as to face each other across the long side 2 of the mold. This magnetic field generator 11, 12
Are connected to the magnetic field power supply controller 19, and the strength of the magnetic field applied by the magnetic field power supply controller 19 is individually controlled.
The magnetic field strengths of the magnetic field generators 11 and 12 may be industrially normally used, with the maximum magnetic field strength being about 0.2 Tesla to 0.4 Tesla.

The magnetic field applied from the magnetic field generators 11 and 12 may be a static magnetic field by a direct current, but as described above, a moving magnetic field in which the magnetic field moves in the horizontal direction is preferable. In the case of the moving magnetic field, not only the magnetic field strength but also the moving direction of the magnetic field can be controlled individually, so that the flow control becomes easier. In the moving magnetic field, the discharge flow 10 is decelerated by setting the moving direction of the moving magnetic field from the mold short side 3 side to the immersion nozzle 8 side, and conversely, the moving direction is changed from the immersion nozzle 8 side to the mold short side 3 side. As a result, the discharge flow 10 is accelerated. In the case of a moving magnetic field, the magnetic field generators 11 and 12 do not need to face each other with the mold long side 2 interposed therebetween, and the discharge flow 10 can be controlled simply by arranging the magnetic field generators 11 and 12 on the back surface of the mold long side 2 on one side. However, when the magnetic field strength is attenuated when it is arranged only on the back surface on one side, it is necessary to arrange a moving magnetic field generator having a high magnetic field strength.

The copper plate on the long side 2 of the mold is provided with a plurality of holes in the width direction of the long side 2 of the mold, and is used as a measurement point 15 for measuring the temperature of the copper plate on the long side 2 of the mold in the mold 1. At each measurement point 15, a thermocouple 16 as a temperature measuring element is inserted into the hole of the copper plate,
It is arranged in contact with the copper plate at the bottom of the hole. Then, the temperature of the copper plate on the long side of the mold is measured by the thermometer main body 17 connected to the thermocouple 16. It is preferable that the measurement points 15 are arranged side by side in the horizontal direction, the distance between the measurement points 15 is 200 mm or less, and the distance from the meniscus 13 is 300 mm or less. If the distance between the measurement points 15 exceeds 200 mm, the number of the measurement points 15 is too small to detect the flow pattern inaccurately, and the distance from the meniscus 13 is 300 mm.
This is because if the temperature exceeds the value, the temperature of the copper plate on the long side 2 of the mold is affected by the discharge flow 10 flowing in the horizontal direction, and similarly the detection of the flow pattern becomes inaccurate.

The temperature of the copper plate on the long side of the mold measured by the thermometer body 17 is sent to the data analyzer 18, and the rate of increase or decrease of the temperature of the copper plate at each measurement point 15 is analyzed. At the same time, in the width direction of the long side 2 of the mold, the distribution of the measurement points 15 having similar changes in the temperature of the copper plate is analyzed. Then, based on these analysis data, the data analysis device 18 detects the molten steel flow pattern in the mold 1, and sends a signal of the detected flow pattern to the magnetic field power supply control device 19. Magnetic field power supply control device 19
Controls the magnetic field intensity applied from the magnetic field generators 11 and 12 individually based on the transmitted flow pattern signal to control the flow pattern to be pattern B.
The magnetic field strength is adjusted by increasing or decreasing the current supplied to the magnetic field generators 11 and 12. In the case of a moving magnetic field (using an AC power supply), the magnetic field strength can be adjusted even by changing the frequency of the current. In the case of the pattern A, the flow pattern is controlled by increasing the magnetic field strength and discharging the flow 10.
When the discharge flow 10 is decelerated or the pattern C is obtained, the magnetic field strength in the deceleration direction is weakened or the magnetic field strength in the acceleration direction is increased to accelerate the discharge flow 10 to form the pattern B together. it can.

Immediately below the mold 1, displacement gauges 20, 20a, 20b, 20 for measuring the surface shape of the solidified shell 5 are provided.
c, 20d are arranged, displacement gauges 20, 20a, 20b,
20 c and 20 d are connected to the arithmetic unit 21. Each of the displacement gauges 20, 20a, 20b, 20c, 20d can be moved in the width direction of the cast piece by a moving device (not shown), and the surface shape of the solidified shell 5 of the entire width of the cast piece can be measured. You can Displacement gauges 20, 20a, 20b, 20
Displacement meters 20, 20a, 20b, 20c, 20d are used for c and 20d, and distance measuring devices such as eddy current distance meters are used.
The distances between the displacement gauges 20, 20a, 20b, 20c, 20d and the solidification shell 5 are measured with, and the calculator 2 is based on the measured values.
1 performs analysis processing to determine the surface shape such as unevenness in the width direction of the solidified shell 5. Then, the computer 21 estimates the heat transfer resistance between the copper plate on the long side 2 of the mold in the width direction of the slab and the solidification shell 5 from the surface shape thus determined, and the estimated heat transfer resistance is analyzed by the data analysis device 18 Send to.

The data analysis device 18 can correct the copper plate temperature on the long side 2 of the mold based on the transmitted heat transfer resistance data, and detect the molten steel flow pattern in the mold 1 from the corrected copper plate temperature. . As described above, the data analyzer 18 is also configured to detect the flow pattern of the molten steel 4 from the measured copper plate temperature without using the heat transfer resistance data, but the corrected copper plate temperature It becomes more accurate by detecting from. In particular, the carbon content is 0.1 to 0.
In the case of 15 wt% carbon steel in the hypoperitectic region, the thickness of the solidified shell 5 is likely to be non-uniform in the width direction of the slab, and unevenness is generated on the surface of the solidified shell 5, so it was corrected by heat transfer resistance. If the copper plate temperature is used, an accurate flow pattern can be detected.

The method of correcting the copper plate temperature is, for example, that the concave portion of the solidified shell 5 is in poor contact with the copper plate on the long side of the mold, and the heat transfer resistance is lowered, and the temperature of the copper plate on the long side of the mold measured is reduced accordingly. Therefore, by correcting the heat transfer resistance of the concave portion of the solidified shell 5 so as to be equal to that of the convex portion, the copper plate temperature on the long side of the mold of the concave portion is corrected to the high temperature side. Before the start of casting, the discharge angle and the cross-sectional area of the discharge hole 9 of the immersion nozzle 8, the immersion depth of the immersion nozzle 8, the injection amount of the molten steel 4 into the mold 1 per unit time, the applied magnetic field strength, Also, the casting conditions such as the amount of Ar blown in are appropriately selected, and the molten steel flow pattern in the mold 1 is set as the pattern B, and the casting is started.

In this embodiment, the refractory rod 26 is immersed in the meniscus 13 to a depth of about 100 mm, and the pressure sensor 27 for detecting the force acting on the refractory rod 26.
The surface flow velocity was measured from the force acting on the refractory rod 26 by the surface flow of the molten steel 4 at several points of the meniscus 13, and it was confirmed that the flow pattern was a predetermined pattern. Since the three flow patterns have different surface velocity distributions, the flow patterns can be analogized. still,
The refractory rod 26 and the pressure receiving sensor 27 are arranged for confirmation, and do not necessarily have to be arranged in carrying out the present invention.

In the above description, the magnetic field generators 11 and 12 are divided in the width direction of the mold long side 2 with the immersion nozzle 8 as a boundary. It can also be implemented in a generator. In that case,
When using the moving magnetic field, it is necessary to connect the magnetic field power supply control device 19 in advance so that the moving directions of the left and right magnetic fields are opposite to each other with the immersion nozzle 8 as a boundary. However, compared with the divided magnetic field generators 11 and 12, the flow control is slightly difficult with one magnetic field generator. Further, in the above description, five displacement gauges are used for description, but the number of displacement gauges may be appropriately determined depending on the width of the slab and the moving speed of the displacement gauge.

[Embodiment 1] An embodiment of the continuous casting machine shown in FIGS. 3 and 4 will be described. The slab size is thickness 2
A low carbon Al killed steel having a width of 50 mm and a width of 1600 mm was cast at a drawing speed of 2.5 m / min. The magnetic field to be applied was a moving magnetic field, and the center of the magnetic field generator in the casting direction was at a position 150 mm from the lower end of the discharge hole. The amount of Ar blown into the molten steel outflow hole is 9 Nl / min. The copper plate on the long side of the mold was measured at 130 mm from the upper end (at a position of 50 mm from the meniscus) with holes at intervals of 50 mm and thermocouples were arranged on the copper plate on the long side of the mold.

FIG. 5 shows an example of measuring the temperature of the copper plate on the long side of the mold at two measurement points A and B. As shown in the figure, at time T ₁ -ΔT, the temperature at point B was higher than the temperature at point A, but immediately before time T ₁ , the temperature at point A started to rise and the temperature at point B was increased. starts to descend, and the temperature is reversed at the two measurement points of points a and B before and after the time T _1, then the time T ₁ + temperature while reversing both point a and point B in ΔT is stable Was there.

FIG. 6 shows changes with time in temperature at each measurement point of the entire length of the long side of the mold before and after the time T ₁ .
In FIG. 6, a ● mark indicates a measurement point 15 where the temperature does not change around time T ₁ , a ⊚ indicates a measurement point 15 at which the temperature rises, and a × indicates a measurement point 15 at which the temperature decreases. As shown in the figure, the measurement points where the temperature has risen are distributed on the side of the short side 3 of the mold, and the measurement points where the temperature has dropped are distributed at the intermediate position between the immersion nozzle 8 and the short side 3 of the mold. It can be seen that the measurement points where the rise is and the measurement points where the fall are showing a characteristic distribution. still,
FIG. 6 also shows the two measurement points A and B shown in FIG.

FIG. 7 shows the result of detecting the molten steel flow pattern in the mold based on the above temperature analysis result. As shown in FIG. 7, at time T ₁ -ΔT, pattern B, time T ₁
At + ΔT, pattern A was detected.

FIG. 8 is a diagram showing the distribution of the surface flow velocity of the molten steel in the mold measured with a refractory rod at the same time. At time T ₁ -ΔT, the flow is toward the center of the mold on the side of the immersion nozzle with the intermediate position between the immersion nozzle and the short side of the mold as the boundary, and conversely, on the side of the short side of the mold, that is, the flow toward the short side of the mold, that is, , Pattern B flow. However, at time T ₁ + ΔT, the surface flow is from the short side of the mold to the center of the mold, that is,
It was pattern A. Thus, from the distribution of the surface flow of molten steel, pattern B, time T ₁ + Δ at time T ₁ −ΔT.
In T, it was confirmed as pattern A, which proves that the pattern detected from the measurement of the copper plate temperature is accurate.

Therefore, the current supplied to the magnetic field generator was increased to increase the strength of the moving magnetic field on the left and right of the immersion nozzle, and the discharge flow was decelerated. FIG. 9 shows the results of measuring the temperature changes at the two measurement points A and B while continuing casting in this state. Immediately after changing the supplied current A
The temperature at the point decreased, the temperature at the point B increased, and stabilized in the same state as at time T ₁ -ΔT. It was confirmed by a refractory rod that the distribution of the surface flow in the meniscus was also the same as that at time T ₁ -ΔT.

As a result of rolling the slab obtained in this example into a thin steel sheet, the amount of mold powder defects was low,
We were able to achieve a high yield. The reference numerals in FIGS. 6 and 7 are the same as those in FIGS. 3 and 4.

[Embodiment 2] An embodiment of the continuous casting machine shown in FIGS. 3 and 4 will be described. The slab size is thickness 2
50 mm, width 1600 mm, carbon content 0.1
2 wt% carbon steel was cast at a drawing speed of 1.8 m / min. The magnetic field to be applied was a moving magnetic field, and the center of the magnetic field generator in the casting direction was at a position 150 mm from the lower end of the discharge hole. The amount of Ar blown into the molten steel outflow hole is 9 Nl / min
Is. The copper plate on the long side of the mold was measured at 130 mm from the upper end (at a position of 50 mm from the meniscus) with holes at intervals of 50 mm and thermocouples were arranged on the copper plate on the long side of the mold.
In this example, the surface shape of the solidified shell was measured with five displacement gauges provided directly below the mold to correct the temperature of the copper plate on the long side of the mold.

FIG. 10 is a graph showing measured data of the copper plate on the long side of the mold at a certain time, the broken line shows the temperature of the copper plate on the long side of the mold before correction, and the solid line shows the temperature of the copper plate on the long side of the mold after correction. The heat transfer resistance was estimated by aligning the gap between the copper plate on the long side of the mold and the solidified shell to a standard value, and the temperature of the copper plate on the long side of the mold was corrected. It was difficult to accurately grasp the change over time of the copper plate on the long side of the mold because the temperature before correction was so high that it was difficult to accurately grasp the changes over time in the copper plate on the long side of the mold. Met.

FIG. 11 shows the molten steel flow velocity measured with a refractory rod immersed in a meniscus in the vicinity of the measurement point shown in FIG. 10 at the same time. A time zone in which the molten steel flow velocity was high occurred at the same time as the time zone in which the temperature of the copper plate on the long side of the mold in FIG. 10 was high. Thus, by correcting the temperature of the copper plate on the long side of the mold from the surface shape of the solidified shell, the flow pattern could be detected more accurately.

Best Mode 2 (Method for Estimating Molten Steel Flow Pattern and Apparatus therefor) The inventors of the present invention, in order to detect the molten steel flow condition with high accuracy even if there is a complicated molten steel flow near the meniscus, The installation position of the temperature measuring element to be buried in was investigated. Primarily,
The installation intervals of temperature measuring elements in the mold width direction were examined. Among the complicated molten steel flow in the vicinity of the meniscus, the molten steel flow velocity profile in the vicinity of the meniscus along the mold width direction is particularly important for quality control.Therefore, using the continuous casting machine used in the examples described later, refractory rods were used. One end of the molten steel was immersed in a meniscus, and the molten steel flow velocity profile along the width direction of the mold near the meniscus was measured by a molten steel anemometer for measuring the molten steel flow velocity by measuring the force applied to the refractory rod by the molten steel flow with a load cell. The measurement of the molten steel flow velocity profile was carried out by changing the combination of the slab drawing speed and the slab width to three levels of levels 1 to 3. Table 1 shows the casting conditions of each level. Moreover, the measurement results of the molten steel flow velocity profile near the meniscus at Levels 1 to 3 are shown in FIGS.
In FIGS. 12 to 14, in the meniscus molten steel flow velocity on the vertical axis, a “positive” value represents the flow from the mold short side to the immersion nozzle side, and a “negative” value represents the flow in the opposite direction. In the present invention, the molten steel flow velocity of the meniscus will be represented in this way.

[0063]

[Table 1]

As shown in FIGS. 12 to 14, the wavelength of the molten steel flow velocity profile near the meniscus along the width direction of the mold, that is, the wavelength of the molten steel flow velocity is 17 at level 1.
50mm, 800mm for Level 2, 880m for Level 3
It is understood that m is about 800 to 1800 mm.

In order to accurately capture this molten steel flow velocity profile with the temperature measuring element embedded in the copper plate of the mold, at least 5 temperature measuring points are required in one wavelength, as shown in FIG. FIG. 15 shows the wavelength of molten steel flow velocity near the meniscus in correspondence with the mold copper plate temperature, and the experience of the present inventors shows that the mold copper plate temperature increases as the molten steel flow velocity increases. ing.

Therefore, the high and low wavelengths of the molten steel flow velocity are from 800 to
In the case of 1800 mm, it suffices to install the temperature measuring elements at intervals of 200 to 450 mm. However, as shown in FIGS. 12 to 14, the molten steel flow velocity profile in the vicinity of the meniscus varies depending on the casting conditions even with the same continuous casting machine, so that the wavelength of the shortest molten steel flow velocity can be detected. Therefore, it is necessary to install the temperature measuring elements at intervals of 200 mm or less.

Second, the installation position of the temperature measuring element in the slab withdrawal direction was examined. Since the present invention aims to estimate the molten steel flow in the vicinity of the meniscus, it is necessary to install the temperature measuring element as close to the meniscus as possible. However, the position of the meniscus fluctuates in the slab drawing direction due to the delicate fluctuation of the flow rate of the molten steel injected into the mold and the slab drawing speed. The fluctuation amount is generally about ± 10 mm at the maximum. The installation position of the temperature measuring element must be below the meniscus position variation range. This is because when the meniscus falls below the temperature measuring element position in the slab drawing direction, the measured mold copper plate temperature greatly drops, and a large error occurs in the estimation of molten steel flow near the meniscus. From the above, the upper limit of the installation position of the temperature measuring element is set to 1 from the meniscus position to the slab drawing direction.
The positions were separated by 0 mm.

Next, the lower limit of the temperature measuring element in the slab drawing direction was examined. This depends on how deep the molten steel flow near the meniscus is from the meniscus to a depth below. In order to examine this, a water model device having a mold width of 1500 mm was used to measure the flow velocity distribution from the meniscus position to a position 195 mm below at positions 225 mm and 375 mm from the mold short side. FIG. 16 is a diagram showing the results, where (A) shows the measurement result at a position of 225 mm from the mold short side, and (B) shows the measurement result at a position of 375 mm from the mold short side. Is the average flow velocity, and the length of the line indicates the flow velocity range. First
As shown in FIG. 6, at the two measured positions, the flow velocity is gradually attenuated up to a position 135 mm below the meniscus, but below that, the flow velocity is rapidly attenuated.
Therefore, from this result, the lower limit of the installation position of the temperature measuring element in the slab drawing direction was set to a position separated by 135 mm from the meniscus position.

Thirdly, the distance from the molten steel side surface of the mold copper plate to the tip of the temperature measuring element was examined. If this distance is too long, the delay in the response time of the temperature measuring element becomes large, and it becomes impossible to accurately follow the temporal change of the molten steel flow in the vicinity of the meniscus. Therefore, first, it was investigated how much the molten steel flow velocity near the meniscus fluctuates with the above-mentioned immersion rod type molten steel flow velocity meter. Then, the autocorrelation coefficient of the measured molten steel flow velocity was calculated in order to obtain the periodicity of the temporal change of the molten steel flow velocity. The calculation result is shown in FIG. In this example, as shown in FIG. 17, it is found that the molten steel flow velocity near the meniscus has a periodicity of 9.3 seconds. The x mark in the figure represents the boundary of each cycle.
The present inventors conducted similar periodicity investigations under other casting conditions, and found that they sometimes have a periodicity of 9 to 30 seconds. Based on the results of these investigations, the following examination was made on the buried depth of the temperature measuring element for estimating the molten steel flow velocity in the vicinity of the meniscus having such periodicity.

The 18th model is a model in which the temperature change on the molten steel side surface of the mold copper plate becomes the output of the temperature measuring element embedded in the mold copper plate.
It is replaced with an electrical equivalent circuit having a distributed constant as shown in the figure. If this distributed constant circuit is replaced with a lumped constant circuit as shown in FIG. 19 for simplification, this is R
It is a low-pass filter using a C integrator circuit. The cutoff frequency of this circuit is expressed by the equation (1). However, in the equation (1), fo is a cutoff frequency, R is a DC resistance component, and C is a capacitance component. fo = 1 / (2π × R × C) (1)

As described above, in the present invention, it is necessary to grasp the fluctuation of the molten steel flow velocity in the vicinity of the meniscus in the cycle of 9 seconds, that is, the fluctuation of the molten steel side surface temperature of the mold copper plate. Assuming that this cycle is the cut-off point, and the temperature variation of the mold copper plate having a longer cycle than that is measured by the temperature measuring element, the product of R × C at this time is given by equation (2). 2π × R × C = 9 (2) Therefore, from the equation (2), R × C = 1.4 seconds. Next, the distance from the molten steel side surface of the mold copper plate to the tip of the temperature measuring element was calculated so that the product of R × C would be 1.4 seconds. FIG. 20 shows a mold at each position in the mold copper plate when a step signal for increasing the temperature from 25 ° C. to 300 ° C. is given to the surface of the mold copper plate on the molten steel side, and the surface temperature of the mold copper plate on the cooling water side is constant at 25 ° C. The change in copper plate temperature is represented by solving an unsteady one-dimensional heat transfer equation. The horizontal axis of FIG. 20 shows the elapsed time (t) from the time when the step signal is input, and the vertical axis shows the mold copper plate temperature (T _∞ ) when the steady state is reached as the denominator, and the mold copper plate temperature at that time (T). The temperature ratio (Ti /
T _∞ ). Further, FIG. 20 shows ratios (Ti / T _∞ ) at a plurality of positions where the distance (x) from the molten steel side surface of the mold copper plate to the cooling water side as a starting point is different, and the numerical values given to the curves in the figure are It is the distance (x) expressed in mm.
Here, the curve in FIG. 20 can be approximated by the equation (3). Ti = {1-exp [-t / (R * C)]} * T [ _infinity ] (3) Further, when t = R * C, the ratio (Ti / T [ _infinity] ) = 0.6.
It is 3. Therefore, if there is a temperature measuring element at a distance (x) such that the ratio (Ti / T _∞ ) ≧ 0.63 with t = R × C = 1.4 (sec), R × of this temperature measuring element The product of C is 1.4 seconds or less, and it is possible to capture the change in the mold copper plate temperature with the above-described fluctuation period of 9 seconds or more, that is, the change in the molten steel flow velocity near the meniscus. The distance (x) that satisfies this condition is the 20th
As shown in the figure, it can be seen that it is 16 mm or less. Therefore, in the present invention, the distance from the molten steel side surface of the mold copper plate to the tip of the temperature measuring element is set to 16 mm or less. Next, a method for estimating molten steel flow in a mold using the above temperature measuring device will be described. First, the principle of a method of estimating the molten steel flow velocity in the mold from the mold copper plate temperature will be described.

FIG. 21 is a diagram schematically showing the temperature distribution from the molten steel to the cooling water for the mold copper plate in the process of heat conduction from the molten steel in the mold to the cooling water for the mold copper plate through the mold copper plate. Is. As shown in FIG. 21, between the molten steel 101 and the cooling water 105 for the mold copper plate, the solidified shell 1
02, mold powder layer 103, and mold copper plate 104
Of each of the heat conductors of the
Is embedded in the mold copper plate 104, and the temperature inside the mold copper plate 104 is measured. In the figure, To is the temperature of the molten steel 101,
T _L is the interface temperature between the solidified shell 102 and the molten steel 101, T _L
S is the boundary temperature between the solidified shell 102 and the mold powder layer 103, T _P is the surface temperature of the mold powder layer 103 on the mold copper plate 104 side, T _mH is the surface temperature of the mold copper plate 104 on the mold powder layer 103 side, and T _mL is Mold copper plate 1
04, the surface temperature of the cooling water 105 side, Tw is the cooling water 105
Is the temperature of.

In this case, from the molten steel 101 to the cooling water 105.
The total thermal resistance obtained by combining the thermal resistances of the heat conductors in equation (4) is
It is represented by. However, in the equation (4), R: general heat resistance
Anti, α: Convection heat transfer coefficient between molten steel and solidified shell, λ
_S : Thermal conductivity of solidified shell, λ _P : Mold powder layer
Thermal conductivity of, λ_m : Thermal conductivity of copper mold plate, h_m :the mall
Heat transfer coefficient between the powder layer and the copper mold, h_W : Casting
Heat transfer coefficient between the copper plate and the cooling water, d_S : Solidified shell
Thickness, d_P : Thickness of mold powder layer, d_m : Mold copper plate
It is the thickness.     R = (1 / α) + (d_S/ λ_S) + (d_P/ λ_P) + (1 / h_m) + (d_m/ λ_m) + (1 / h_W)… (4) Here, mold copper plate thickness (d_m ), The thermal conductivity of the mold copper plate (λ
_m ) Is a fixed value depending on the equipment. In addition, solidification
Thermal conductivity (λ_S ) Is fixed if the steel type is decided
It is a value. Also, the thickness of the mold powder layer (d_P ) Is moo
Type of powder and mold vibration amplitude, frequency, and wave
It is a numerical value that is fixed if the shape and the slab drawing speed are determined.
It Also, the thermal conductivity of the mold powder layer (λ_P ) Is moo
It is known that it is almost constant regardless of the type of powder.
Has been. Also, the heat transfer coefficient between the mold copper plate and the cooling water
(H_W ) Is the flow rate of the cooling water 105, the surface of the mold copper plate 104
It is a fixed value if the roughness is determined. Also, mold
Heat transfer coefficient between powder layer and mold copper plate (h_m ) Mo
Once the type of the field powder is decided, it will be decided to be a constant value.
It

However, the convective heat transfer coefficient (α) between the molten steel and the solidified shell is a value that changes depending on the molten steel flow velocity along the surface of the solidified shell 102, and the convective heat transfer coefficient (α) is (5) ) Can be expressed by a plate approximation formula. However, in the equation (5), Nu: Nusselt number, λ
₁ : Thermal conductivity of molten steel, X ₁ : Representative length of heat transfer. α = Nu × λ ₁ / X ₁ (5) Here, the Nusselt number (Nu) is expressed by equations (6) and (7) for each velocity range of the molten steel flow velocity. However, in the equations (6) and (7), Pr is the number of Plunder, Re is the number of Reynolds, U is the molten steel flow velocity, and Uo is the transition velocity between the laminar flow and the turbulent flow of the molten steel. Nu = 0.664 x Pr ^1/3 x Re ^4/5 (U <Uo) (6) Nu = 0.036 x Pr ^1/3 x Re ^1/2 (U≥Uo) (7) Also, the number of prandles ( Pr) and Reynolds number (Re)
Are expressed by equations (8) and (9), respectively. However, in the equation (9), X _{2 is a} representative length of molten steel flow, and ν is a kinematic viscosity coefficient of molten steel. Pr = 0.1715 (8) Re = U × X ₂ / ν (9)

On the other hand, the heat flux from the molten steel 101 to the cooling water 105 can be expressed by the equation (10). However (10)
In the formula, Q: heat flux from molten steel to cooling water, To: molten steel temperature, Tw: cooling water temperature. Q = (To-Tw) / R (10) The surface temperature of the mold copper plate 104 on the cooling water 105 side is (1
It can be expressed by the equation 1). However, in the equation (11), T _mL is the surface temperature of the copper plate on the cooling water side. T _mL = T _w + Q / h _W (11)

Further, the mold copper plate temperature measured by the temperature measuring element 106 can be expressed by the equation (12). However (1
In the equation (2), T is the temperature of the mold copper plate measured by the temperature measuring element, d is the distance from the surface of the mold copper plate on the molten steel side to the tip of the temperature measuring element. _{T = T mL + Q × (} d m -d) / λ m ... (12) Then, by substituting expression (11) to (12), the mold copper plate temperature (T) is expressed by equation (13) . _{T = Tw + Q / h W} + Q × (d m -d) / λ m ... (13)

In the present invention, the molten steel flow velocity (U) is calculated by using the above equation.
The procedure is described below. First, the measured value of the mold copper plate temperature (T) by the temperature measuring element,
The heat flux (Q) is obtained by substituting it into the equation (13). (13)
In the formula, all the variables on the right side other than the heat flux (Q) are known, so the heat flux (Q) can be calculated backward. Next, by substituting the heat flux (Q) into the equation (10), the overall thermal resistance (R)
Ask for. In this case as well, all variables on the right side other than the total thermal resistance (R) are known, so the total thermal resistance (R) can be calculated backward. Then, the overall heat resistance (R) is substituted into the equation (4) to obtain the convection heat transfer coefficient (α). In this case as well, all variables on the right side other than the convection heat transfer coefficient (α) are known, so that the convection heat transfer coefficient (α) can be calculated backward. The calculated convection heat transfer coefficient (α) is substituted into the equation (5) to obtain the Nusselt number (Nu), and this Nusselt number (Nu) is substituted into the equation (6) or the equation (7) to calculate the Reynolds number )
Ask for. Then, the finally obtained Reynolds number (Re) is substituted into the equation (9) to obtain the molten steel flow velocity (U).

As described above, by grasping the change in the mold copper plate temperature caused by the change in the convection heat transfer coefficient between the molten steel and the solidified shell due to the molten steel flow velocity, the molten steel flow velocity along the solidification interface can be estimated. it can.

Next, a method for estimating the flow pattern of molten steel in the mold from the temperature of the copper plate in the mold will be described. The flow pattern of the molten steel in the mold is the slab drawing speed, the immersion nozzle shape,
There are various flow patterns depending on the flow rate of Ar blown into the immersion nozzle, and typical examples thereof are shown in FIG.
In addition, FIG. 22 also shows the temperature measurement result of the copper plate temperature on the long side of the mold at that time in the width direction of the mold. In addition, in FIG.
109 is a copper plate on the short side of the mold, 116 is a meniscus, 120 is a dipping nozzle, 121 is a discharge hole, and 122 is a discharge flow.
The discharge flow 122 is indicated by an arrow in the direction of the flow.
As shown in FIG. 22, it can be seen that the temperature measurement results of the copper plate temperature on the long side of the mold in the width direction of the mold correspond well with the molten steel flow pattern. That is, the discharge flow 122 from the immersion nozzle 120 is predominantly flowing in the portion where the copper plate on the long side of the mold has a high temperature,
This is because the molten steel flow pattern is determined thereby.
At that time, the flow pattern can be easily estimated by finding the number of peaks and the positions of the peaks of the mold copper plate temperature in the mold width direction.

For example, in the pattern 0 of FIG. 22, there is no particularly dominant flow, and the flow is gentle over the entire width direction of the mold, and although the measured value of the temperature measuring element does not show a large difference, the pattern In No. 1, the ascending flow in the vicinity of the immersion nozzle accompanying the floating of Ar blown into the immersion nozzle 120 is dominant, and the measured temperature value in the vicinity of the immersion nozzle becomes high. This is the case where one temperature peak is observed near the immersion nozzle. In the pattern 2, since the discharge flow 122 from the immersion nozzle 120 collides with the mold short side copper plate 109 and flows,
The measured value near the copper plate on the short side of the mold becomes high. At this time, a temperature peak appears near the copper plate 109 on the short side of the mold, and there are two temperature peaks in the entire mold. In the pattern 3, the ascending flow in the vicinity of the immersion nozzle due to the Ar blown into the immersion nozzle 120 and the flow due to the inertial force of the discharge flow 122 are dominant, and the temperature measurement values are measured both in the vicinity of the immersion nozzle and in the vicinity of the copper plate on the short side of the mold. Get higher At this time, there are three temperature peaks over the entire mold width. By the way, the pattern No. shown in FIG.
The integer part of indicates the number of temperature peaks in the entire mold width direction,
The decimal points indicate that the peak temperature position on the short side of the mold is located away from the copper plate 109 on the short side of the mold on the immersion nozzle 120 side.

Finally, a method for estimating the presence or absence of drift of molten steel in the mold from the mold copper plate temperature will be described. Normally, the molten steel injected into the mold from the immersion nozzle has a symmetrical flow in the mold width direction with the immersion nozzle at the center, and therefore the temperature of the copper plate on the long side of the mold is also symmetrical. Therefore, when the position of the maximum value of the copper plate temperature is not bilaterally symmetrical on the left and right in the width direction of the copper plate on the long side of the mold, it can be easily estimated that the drift has occurred. Even if the position of the maximum value of the copper plate temperature is symmetric, if there is a difference in the maximum values, the discharge flow rate is different between the left and right, and in this case as well, it can be estimated that a drift has occurred.

The present invention will be described with reference to the drawings. FIG. 23 is a schematic front sectional view of a continuous casting machine mold part showing one embodiment of the present invention, and FIG. 24 is a schematic side sectional view. In FIG. 23 and FIG. 24, a tundish 118 is provided above the mold 107 composed of the opposing copper mold long side copper plate 108 and the opposing mold short side copper plate 109 installed inside the mold long side copper plate 108. It is arranged. The long side water box 1 is provided on the upper back side and the lower back side of the copper plate 108 on the long side of the mold.
10 is installed, the cooling water 105 supplied from the long side water box 110 at the lower rear portion cools the long side copper plate 108 of the mold through the water passage 111, and is discharged to the long side water box 110 at the upper side. The thickness from the front surface of the mold long side copper plate 108 to the water channel 111, that is, the mold long side copper plate thickness is d _m . Although not shown, the copper plate 109 on the short side of the mold is also cooled in the same manner.

An upper nozzle 123 is provided at the bottom of the tundish 118, and a sliding nozzle 119 including a fixed plate 124, a sliding plate 125, and a rectifying nozzle 126 is arranged in connection with the upper nozzle 123, and further, The immersion nozzle 12 is provided on the lower surface side of the sliding nozzle 119.
0 is placed and the tundish 118 to the mold 107
A molten steel outflow hole 127 is formed.

The molten steel 101 poured into the tundish 118 from a ladle (not shown) is provided under the immersion nozzle 120 via the molten steel outflow hole 127, and the mold 10 is used.
A discharge flow 122 is injected into the mold 107 from the discharge hole 121 immersed in the molten steel 101 in the mold 7 toward the copper plate 109 on the short side of the mold. Then, the molten steel 101 is cooled in the mold 107 to form the solidified shell 102, which is drawn below the mold 107 to become a cast piece. At that time, mold powder 117 is added on the meniscus 116 in the mold 107,
Mold powder 117 is melted and solidified shell 102
Flows between the mold 107 and the mold 107, and the mold powder layer 10
3 is formed.

The meniscus 11 is attached to the copper plate 108 on the long side of the mold.
6, a plurality of holes are provided along the width direction of the copper plate 108 on the long side of the mold at a position where the distance from the 6 to the drawing direction of the cast is L and the adjacent installation interval is Z, and the temperature of the copper plate on the long side of the mold 108 is measured. It is the measurement point 112 to be used. At that time, the distance (L) from the meniscus 116 in the slab drawing direction is 10 to 1
The range is 35 mm, and the installation interval (Z) is 200 mm or less. At each measurement point 112, the temperature measuring element 106 is arranged such that the distance from the molten steel side surface of the long side copper plate 108 of the mold to the tip of the temperature measuring element 106 is d, and the tip is in contact with the long side copper plate 108 of the mold. . The distance (d) is 16 mm or less.

On the other hand, the other end of the temperature measuring element 106 is connected to the zero compensator 113, and the electromotive force signal output from the temperature measuring element 106 passes through the zero compensator 113 to the converter 11.
4 and the converter 114 converts the electromotive force signal into a current signal, which is then converted into a current signal by the data analysis device 115.
Entered in.

When the cooling water 105 enters the measuring point 112, the temperature of the copper plate at the temperature measuring contact portion decreases, so that the copper plate temperature cannot be accurately measured. In the present invention, in order to prevent the cooling water 105 from entering the measuring point 112, a stainless steel pipe 128 is installed in the long side water box 110 as shown in FIG. A welded portion 130 by welding is provided on the entire circumference of the contact surface with the water box 110, the temperature measuring element 106 is installed by penetrating the inside of the pipe 128, and a groove is formed on the copper plate 108 on the long side of the mold around the measuring point 112. The seal packing 129 that contacts the copper plate 108 on the long side of the mold and the water box 110 on the long side is installed therein. The coil-shaped spring (not shown) is used to measure the temperature measuring element 106.
Is pressed against the copper plate 108 on the long side of the mold. Note that FIG. 25 is a schematic side cross-sectional view of the mold part of the continuous casting machine showing the mounting structure of the temperature measuring element, and reference numeral 131 in the drawing is a back frame.

With this structure, the long side water box 1
In the inside of 10, the temperature measuring element 106 and the cooling water 105 are completely separated, the cooling water 105 in the long side water box 110 does not enter the measuring point 112, and the mold long side copper plate 108
The cooling water 105 through the contact gap between the long side water box 110 and
The seal packing 12
9 prevents entry into the measuring point 112. Instead of welding, a resin seal or a hard solder seal may be used. Also, the seal packing 129 is the long side water box 110.
You may provide a groove in the side and install in it. Temperature measuring element 10
6 may be of any type as long as it can measure a temperature with an accuracy of ± 1 ° C. or higher among thermocouples, resistance thermometers and the like.

The data analyzer 115 estimates the flow pattern of the molten steel in the mold from the temperature distribution of the copper plate temperature on the long side of the mold in the width direction of the mold, the peak position and number of the temperature, and the mold length with the immersion nozzle 120 as the boundary. The drift of molten steel in the mold is estimated and displayed from the position and the maximum value of the maximum values of the mold copper plate temperature on the left and right of the copper plate 108 in the width direction. Furthermore, based on the molten steel flow velocity measurement principle described above, the mold long sides copper plate temperature (T), the mold long sides copper plate thickness (d _m), the distance (d), the molten steel temperature by using the data of the coolant temperature and the like, The molten steel flow velocity (U) at each measurement point 112 is calculated and displayed. Incidentally, among the 15 variables constituting the equations (4) to (13), the solidification shell thickness (d _S ) and the mold powder layer thickness (d _P ) are variables that vary depending on the casting conditions and cannot be directly measured during casting. ), The heat transfer coefficient between the mold copper plate and the cooling water (h
There are three variables of _W ), but these three variables correspond to the casting conditions at the time of measuring the copper plate temperature of the mold by investigating the changes in the numerical values due to the change of the casting conditions by the actual machine test or the simulated test. The molten steel flow velocity (U) may be calculated based on the numerical value. The other 12 variables can be determined by the equipment conditions and the physical property values.

Table 2 shows that the slab drawing speed is 2.0 m / mi.
It shows an example of each variable in the casting conditions of n and 1.3 m / min. Further, based on the variables shown in Table 2 in FIG. 26, the mold copper plate temperature (T) and the molten steel flow velocity (U) are shown. The result of obtaining the relationship is shown. As shown in FIG. 26, even if the mold copper plate temperature is the same, the molten steel flow velocity is significantly different depending on the cast strip drawing speed, and it is understood that the molten steel flow velocity can be estimated from the mold copper plate temperature. The transition velocity (Uo) between the laminar flow and the turbulent flow of the molten steel was calculated as 0.1 m / sec, and Vc in Table 2 and FIG. 26 is the slab drawing speed.

[0091]

[Table 2]

By installing the temperature measuring element 106 on the mold copper plate as described above, even if there is a complicated molten steel flow in the vicinity of the meniscus 116, it is possible to accurately change the temperature of the mold copper plate due to the molten steel flow in the mold. Can be measured. And
Based on the mold copper plate temperature measured in this way, the molten steel flow velocity in the mold, the flow pattern of the molten steel in the mold, and the drift of the molten steel in the mold are estimated, so that the estimation accuracy is improved and the operation is hindered. Without this, online estimation is possible.

In the above description, the temperature measuring elements 106 are installed in one row in the width direction of the mold 107, but a plurality of rows may be installed in the casting direction. Further, in the above description, the temperature measuring element 106 is installed only on one side of the mold long side copper plate 108, but it may be installed on both mold long side copper plates 108. Further, although the above description has explained the mold 107 having a rectangular cross-sectional shape, the present invention is not limited to the rectangular cross-sectional shape of the mold 107, and can be applied even if the mold has a circular shape, for example.

[Example 1] An example in which the molten steel flow velocity was estimated by using the slab continuous casting machine and the mold copper plate temperature measuring device shown in Fig. 23 will be described below. The continuous casting machine is a vertical bending mold having a vertical portion of 3 m, and can cast a slab of maximum 2100 mm. Table 3 shows the specifications of the continuous casting machine used.

[0095]

[Table 3]

The long side mold copper plate has a thickness (d _m ) of 40 mm, and an alumel chromel (JIS thermocouple K) is used as a temperature measuring element. When the distance (d) is 13 mm, the distance (Z) between adjacent thermocouples is 66.5 mm, and the distance (L) from the meniscus is 50 mm, the length in the mold width direction is 2100 m.
The thermocouple was buried over m. And thickness 220m
m, width 1650 mm, slab drawing speed 1.85 m
/ Min (hereinafter, referred to as "casting condition 1") and a slab having a thickness of 220 mm and a width of 1750 mm was cast at a slab drawing speed of 1.75 m / min (hereinafter referred to as "casting condition 2"). In this case, the copper plate temperature on the long side of the mold was measured. Table 4 shows the casting conditions collectively.

[0097]

[Table 4]

FIGS. 27 and 28 are examples of temperature measurement data of the mold copper plate temperature in the mold width direction at a certain moment under the casting condition 1 and the casting condition 2, respectively. In these figures, the horizontal axis is the position in the width direction of the cast piece, the central position "0 mm" is the center position in the width direction of the cast piece, and the position of the immersion nozzle (hereinafter, the position in the width direction of the cast piece is the same. Shown in notation). As shown in FIG. 27 and FIG. 28, the temperature of both skirts in the width direction of the slab greatly drops. This is because the copper plate on the short side of the mold is installed in the vicinity where the temperature largely drops. Because.

29 and 30 show the molten steel flow velocity calculated from the mold copper plate temperatures shown in FIGS. 27 and 28, using the numerical values of the variables shown in Table 2. Among the variables in Table 2, the solidified shell thickness (d _S ) was 0.00362 m under the casting condition 1 and 0.00372 m under the casting condition 2. Further, in FIG. 29 and FIG. 30, the molten steel flow velocity value measured by the above-mentioned immersion rod type molten steel flow velocity meter at the time when the mold copper plate temperature was measured is indicated by ●. From these results,
It was confirmed that the molten steel flow velocity of 50 mm below the meniscus estimated from the mold copper plate temperature and the molten steel flow velocity near the meniscus by the dipping rod were in good agreement.

Example 2 Using the same continuous casting machine and mold copper plate temperature measuring device as in Example 1, Ar was placed in the dipping nozzle.
250 mm thickness, width 1 while blowing 10 Nl / min
A 600 mm slab was cast at a slab drawing speed of 2.2 m / min, and the flow pattern of the molten steel in the mold was estimated.

The temperature distribution of the copper plate on the long side of the mold after 10 minutes from the start of casting has three temperature peaks at the position of the dipping nozzle and on the copper plates on the short sides of both molds, and is almost symmetrical in the width direction of the mold. The temperature distribution is obtained, and from the result, the above-mentioned 22nd
It could be estimated that it was pattern 3 shown in the figure. In order to confirm this, the molten steel flow velocity in the mold width direction and its direction were measured using the above-mentioned immersion rod type molten steel flow velocity meter. The measurement result is shown in FIG. As shown in FIG. 31, the results obtained by the immersion rod type molten steel anemometer are a flow from the immersion nozzle to the copper plate on the short side of the mold on the side of the immersion nozzle in the mold and a flow in the opposite direction on the side of the copper plate on the short side of the mold. That is, it was confirmed that it was the flow state of pattern 3, and it was in agreement with the result estimated from the copper plate temperature on the long side of the mold.

Also, from the start of the fifth heat of continuous casting, 1
The temperature distribution of the copper plate on the long side of the mold after 0 minutes was different between the left and right of the mold, and the temperature distribution shown in FIG. 32 was obtained. As a result of estimating the flow pattern from this temperature distribution, the left side of the immersion nozzle is pattern 1 having a temperature peak on the immersion nozzle side,
It was estimated that the right side of the immersion nozzle was pattern 2 having a temperature peak on the copper plate side of the mold short side. In order to confirm this, the molten steel flow velocity in the mold width direction and its direction were measured using the above-mentioned immersion rod type molten steel flow velocity meter. The measurement result is the third
It is shown in FIG. As shown in FIG. 33, the result obtained by the immersion rod type molten steel anemometer is the flow from the immersion nozzle to the copper plate on the short side of the mold on the left side of the mold, that is, pattern 1, and on the right side of the mold, the opposite mold. The flow was from the short side to the dipping nozzle, that is, pattern 2, which coincided with the result estimated from the copper plate temperature on the long side of the mold.

Example 3 Using the same continuous casting machine and mold copper plate temperature measuring device as in Example 1, Ar was placed in the dipping nozzle.
10 Nl / min, thickness 250 mm, width 160
A 0 mm slab was cast at a slab drawing speed of 2.6 m / min to estimate the presence or absence of drift of molten steel in the mold. 10 minutes after the start of casting, the temperature distribution of the copper plate on the long side of the mold was a distribution that was substantially symmetrical in the width direction of the mold, and the maximum temperature was 180.5 ° C on the left side and 181 ° C on the right side. Since there is no difference between the maximum temperature positions on the left and right, and the maximum values on the left and right are also small, it is estimated that no drift has occurred. In order to confirm this, the molten steel flow velocity in the width direction of the mold and its direction were measured by the above-mentioned immersion rod type molten steel flow velocity meter. The measurement result is shown in FIG. As shown in FIG. 34, the molten steel flow velocity of the meniscus measured by the immersion rod type molten steel flow velocity meter was bilaterally symmetric and no uneven flow was generated, which coincided with the result estimated from the mold copper plate temperature.

[0104] From the start of the third heat of continuous casting, 1
The temperature distribution of the copper plate on the long side of the mold after 0 minutes was different in the left and right directions in the width direction of the mold. The temperature distribution at that time is shown in FIG.
As shown in FIG. 35, the maximum value of the temperature was confirmed by the thermocouple at a position of 598.5 mm from the center of the dipping nozzle on both the left and right sides. The values were 176.5 ° C. on the left side and 18 on the right side.
There was a difference of 8 ° C, which was 4.5 ° C. Since the difference between the maximum values of temperature was large, it was estimated that the drift was occurring. In order to confirm this, the molten steel flow velocity in the width direction of the mold and its direction were measured by the above-mentioned immersion rod type molten steel flow velocity meter. The measurement result is shown in FIG. As shown in FIG. 36, the molten steel flow velocity of the meniscus measured by the immersion rod type molten steel flow velocity meter was different between the left and right of the immersion nozzle, and it was confirmed that uneven flow was generated.

In the present invention, since the temperature measuring element for measuring the temperature of the mold copper plate is installed as described above, even if there is a complicated molten steel flow near the meniscus, the temperature of the mold copper plate caused by the molten steel flow in the mold The change can be accurately measured. Then, based on the mold copper plate temperature measured in this manner, the molten steel flow rate in the mold, the flow pattern of the molten steel in the mold, and the drift of the molten steel in the mold is estimated, so that the estimation accuracy is improved and the operation is performed. Online estimation is possible without any hindrance. As a result, the quality control of the slab is improved, the production of high-quality slab with a high yield is achieved, and its industrial effect is exceptional.

Best Mode 3 (Method of Determining Surface Defects of Continuous Casting Slab) The inventors of the present invention conducted measurement, model experiments, and numerical analysis on an actual machine, and under various casting conditions, the molten steel flow state in the mold, The temperature profile of the mold copper plate in the mold width direction at that time was investigated. FIG. 37 schematically shows a comparison between the flow state of molten steel in the mold and the profile of the mold copper plate temperature. still,
In FIG. 37, 206 is a copper plate on the short side of the mold, 211 is a meniscus, 215 is an immersion nozzle, 216 is a discharge hole, 21
Reference numeral 7 denotes a discharge flow, and the discharge flow 217 shows the direction of the flow with an arrow.

In the pattern 0, there is no particularly dominant flow, the flow is gentle over the entire width direction of the mold, and a large difference does not appear in the measured value of the temperature measuring element in the width direction of the mold. That is, when the temperature peak does not appear significantly, the temperature profile is flat over the entire mold width. In the pattern 1, the upward flow in the vicinity of the immersion nozzle accompanied by the floating of the Ar blown into the immersion nozzle 215 becomes dominant, and in the meniscus 211, the immersion nozzle 215 extends from the mold short side copper plate 20.
The molten steel flows toward 6. Therefore, the temperature distribution in the width direction of the mold copper plate becomes high in the vicinity of the immersion nozzle 215, and one large temperature peak occurs in the vicinity of the immersion nozzle 215. In the pattern 2, the discharge flow 2 from the immersion nozzle 215
The inertial force of 17 is large, and the discharge flow 217 is
After colliding with 06, the molten steel flows from the upper and lower parts of the meniscus 211 toward the dipping nozzle 215 from the copper plate 206 on the short side of the mold. In this case, the molten steel flow velocity at the meniscus 211 is relatively high. At this time, the copper plate temperature in the vicinity of the copper plate 206 on the short side of the mold becomes high, and a large temperature peak has a temperature profile in the vicinity of the copper plate 6 on the short side of the left and right molds.

As described above, the temperature profile can be roughly classified into three types of patterns 0, 1, and 2. However, in reality, there are temperature patterns other than these three types of patterns. For example, the pattern 3 shown in FIG. 37 occurs when both the ascending flow in the vicinity of the immersion nozzle 215 that accompanies the floating of Ar and the inertial force of the discharge flow 217 are dominant.
Temperature peaks appear in the vicinity of 15 and in the vicinity of the copper plate 206 on the short side of the mold, and the temperature profile has three temperature peaks. However, this pattern is pattern 1 and pattern 2.
Can be thought of as a combination with. It was confirmed that in other cases other than this, it was represented by a combination of pattern 0, pattern 1, and pattern 2. From the above investigation, it was found that the molten steel flow condition changes variously depending on the casting conditions and that various temperature profiles exist corresponding to the molten steel flow condition. Then, it was found that it is important and possible to judge from the corresponding temperature profile in consideration of these flow conditions when judging the quality of the surface of the slab.

First, the molten steel flow condition during operation is shown in pattern 1.
The case will be described. When the molten steel flow condition is pattern 1, the floating of Ar is concentrated near the immersion nozzle, and the floating Ar bubble diameter is also large. When the air bubbles separate from the meniscus, the meniscus is disturbed and the mold powder is caught, or the air bubbles themselves are trapped, which causes blow defects. At this time, the maximum value (T _max ) in the temperature distribution in the width direction of the mold copper plate as shown in FIG. 38 (a) can be considered as one factor representing the magnitude of the disturbance of the meniscus due to Ar, Therefore, when the maximum value (T _max ) is too large, the entrainment of the mold powder by Ar can be predicted.

Further, when both a fast flow and a slow flow exist in the meniscus, the gradient of the molten steel flow velocity is related to the shear stress acting on the mold powder, and the larger the gradient value, the more easily the mold powder is eroded. . This gradient of the flow velocity is detected as the gradient of the temperature of the mold copper plate. Therefore,
As shown in FIG. 38 (b), the maximum value minimum value (T _L1) (T _L2) obtained by subtracting the value of the temperature distribution in the mold width direction left around the immersion nozzle (T _L1 -T _L2), the maximum value of the temperature distribution in the mold width direction right (T _R1) from the minimum value (T _R2) among the values obtained by subtracting the (T _R1 -T _R2), the larger the value (hereinafter, the "maximum height temperature difference" Can be considered as another factor representing the magnitude of the disturbance of the meniscus due to Ar, and therefore, the entrainment of the mold powder by Ar can be predicted by the magnitude of the maximum temperature difference.

When the molten steel flow condition is pattern 1, the molten steel of the meniscus flows from the dipping nozzle side toward the copper plate side on the short side of the mold, so that the molten steel temperature on the copper plate side on the short side of the mold becomes low. When the circulation amount of the molten steel is small, so-called skinning and slagging that solidifies the molten steel occur in the meniscus near the copper plate on the short side of the mold. Therefore, the minimum value (T _min ) of the temperature distribution in the width direction of the mold copper plate as shown in FIG. 38 (a) can be considered as one factor representing the circulating amount of molten steel in the meniscus, and , If the minimum value (T _min ) is too small, there is a risk of skinning,
In addition, it can be predicted that blow defects and slag will occur frequently.
Further, the average copper plate temperature (T _ave ) in the entire width direction of the mold as shown in FIG. 38 (c) can be considered as another factor representing the circulating amount of molten steel in the meniscus, and therefore, the average copper plate. It is also possible to predict skinning and shavings depending on the size of the temperature (T _ave ).

Further, the mechanism of generation of slurries is that the consumption of the mold powder increases abnormally due to variations in the physical properties of the mold powder, and the thickness of the molten layer of the mold powder on the meniscus becomes thin, resulting in unmelted mold powder. It is presumed that is generated by adhering to the surface of the solidified shell. In this case, since the consumption of the mold powder increases abnormally, the temperature of the mold copper plate decreases as compared with the case where the consumption of the mold powder is normal. Therefore, by grasping the average copper plate temperature (T _ave ) in the mold width direction and comparing it with the average copper plate temperature (T _ave ) of the typical mold width direction temperature at the slab drawing speed, by grasping the difference, norokami It is possible to predict the occurrence or non-occurrence. Here, the average copper plate temperature (T _ave ) of the typical mold width direction temperature at the slab drawing speed is the average value of the mold width direction copper plate temperature measured at many casting opportunities at the slab drawing speed. Define.

Next, the molten steel flow condition during operation is shown in pattern 2.
The case will be described. Pattern 2 of molten steel flow
As shown, there is a relatively fast molten steel flow in the meniscus.
In this case, the mold covers the meniscus with this flow.
The powder may be scraped. If the molten steel flow velocity is high
The mold copper plate temperature also rises. Therefore, as shown in FIG. 39 (a)
The maximum value (T
_max) Represents the maximum velocity of molten steel in the meniscus
Can be considered as a factor, and thus the maximum value (T _max)But
If it is too large, mold powder will be scraped off
Can be predicted.

Further, the molten steel flow condition is as shown in pattern 2,
If both relatively fast and slow flows exist in the meniscus, as mentioned above, this gradient of molten steel flow velocity is related to the shear stress acting on the mold powder. It will be easier. This gradient of the flow velocity is detected as the gradient of the temperature of the mold copper plate. Therefore, as shown in Figure No. 39 (b), the maximum value of the temperature distribution in the mold width direction left around the immersion nozzle minimum value (T _L1) (T _L2) by subtracting the value (T _L1 -T _L2) And the maximum value (T _R1 ) to the minimum value (T _R1 ) of the temperature distribution on the right side in the mold width direction.
_R2 ) minus the value ( _TR1 - _TR2 ), whichever is larger, that is, the maximum height difference can be considered as a factor representing the magnitude of the flow velocity gradient. It is possible to predict whether or not the mold powder will be cut.

Further, in the case where the molten steel flow condition is pattern 2, when there is a large variation in the molten steel flow velocity of the meniscus on the left and right in the width direction of the mold, vortices are likely to be generated where the flows collide, and the mold powder may be caught. Therefore, as shown in FIG. 39 (c), the absolute value of the difference between the maximum value of the left side temperature distribution (T _L1 ) and the maximum value of the right side temperature distribution (T _R1 ) in the mold width direction (T _R1 ) around the immersion nozzle ( Hereinafter, "maximum left-right temperature difference") can be considered as a factor that represents the degree of drift that affects the entrainment of mold powder by vortices. It is possible to predict the presence or absence of congestion.

Further, when the flow condition of the molten steel in the mold changes, for example, from pattern 1 to pattern 3, or when the flow velocity of discharge on one side is faster than that on the other side even in pattern 2, the inside of the mold is The molten steel flow is disturbed, the meniscus fluctuation amount is increased, and the probability of entrainment of mold powder is increased. Usually, the flow fluctuation observed in the mold gradually changes with a cycle of several tens of seconds, but when it changes in a time shorter than this cycle, the occurrence of mold powder entrainment becomes high. This change in molten steel flow is detected as a temperature fluctuation amount of the mold copper plate temperature per unit time. Therefore, it is possible to grasp the maximum value of the temperature fluctuation amount of the mold copper plate temperature in the width direction of the mold per unit time, and to predict the presence or absence of the mold powder inclusion based on the magnitude of this maximum value.

However, it is necessary to set the temperature measurement position of the copper plate of the mold to a range 10 to 135 mm away from the position of the meniscus in the mold in the slab drawing direction. 10 mm from the meniscus position
The range of less than, because the mold copper plate temperature rises and falls due to the fluctuation of the meniscus during casting, it is not possible to accurately grasp the change of the mold copper plate temperature due to molten steel flow, and in the lower position beyond 135 mm from the meniscus, This is because the amount of change in the temperature of the mold copper plate due to the change in the molten steel flow becomes small, and the amount of change in the mold copper plate temperature cannot be accurately grasped.

By analyzing the widthwise distribution of the temperature of the mold copper plate in this manner, the degree of surface defects of the slab, such as encapsulation of mold powder, skinning, blow flaws, and shavings, can be immediately determined online. be able to.

Incidentally, in FIG. 38, the molten steel flow condition is pattern 1
It is a figure which shows typically the width direction distribution of the mold copper plate temperature at this time, and the maximum value, the minimum value, and the average value of the mold copper plate temperature.
FIG. 9 is a diagram schematically showing the widthwise distribution of the mold copper plate temperature and the maximum and minimum values of the mold copper plate temperature when the molten steel flow condition is pattern 2. In addition, since the temperature measurement value near the copper plate on the short side of the mold becomes low due to the influence of the copper plate on the short side of the mold, the influence of the copper plate on the short side of the mold appears when analyzing the widthwise distribution of the temperature of the mold copper plate in the present invention. The measured values in the range are excluded from the analysis.

The present invention will be described below with reference to the drawings. FIG. 40 is a schematic front cross-sectional view of a mold part of a continuous casting machine to which the present invention is applied. In FIG. 40, a tundish 213 is arranged above a mold 204 composed of a copper plate 205 on the long side of the mold and a copper plate 206 on the short side of the mold which are installed inside the copper plate 205 on the long side of the mold. . An upper nozzle 218 is provided at the bottom of the tundish 213, and a sliding nozzle 214 including a fixed plate 219, a sliding plate 220, and a rectifying nozzle 221 is arranged in connection with the upper nozzle 218, and further, a sliding nozzle 214. An immersion nozzle 215 is disposed on the lower surface side of the molten steel, and a molten steel outflow hole 222 from the tundish 213 to the mold 204 is formed.

From the ladle (not shown) to the tundish 21
The molten steel 201 injected into the No. 3 via the molten steel outflow hole 222 is provided in the lower part of the immersion nozzle 215, and from the discharge hole 216 immersed in the molten steel 201 in the mold 204,
The discharge flow 217 is directed toward the mold short side copper plate 206 and the mold 204
Injected inside. Then, the molten steel 201 is cooled in the mold 204 to form the solidified shell 202, and is drawn below the mold 204 to become a cast piece. Mold powder 212 is added on the meniscus 211 in the mold 204.

The upper nozzle 218 is made of porous brick,
In order to prevent alumina from adhering to the wall surface of the molten steel outflow hole 222, Ar is blown into the molten steel outflow hole 222 from the upper nozzle 218 via an Ar introduction pipe (not shown) connected to the upper nozzle 218. The blown Ar is molten steel 201
At the same time, it passes through the immersion nozzle 215, flows into the mold 204 through the discharge holes 216, floats on the meniscus 211 through the molten steel 201 in the mold 204, penetrates the mold powder 212 on the meniscus 211, and reaches the atmosphere.

On the back surface of the copper plate 205 on the long side of the mold, a width direction of the copper plate 205 on the long side of the mold is set on a straight line in a range 10 to 135 mm away from the meniscus 211 in the drawing direction of the slab and orthogonal to the drawing direction of the slab. A plurality of holes are provided along the measurement point 2 for measuring the copper plate temperature of the long side copper plate 205 of the mold.
It is 07. A temperature measuring element 203 is provided at each measuring point 207.
However, the tip is placed in contact with the long side copper plate 205 of the mold,
It is possible to measure the mold copper plate temperature corresponding to the entire width of the slab. The distance between adjacent measurement points 207 is preferably 200 mm or less. The interval between each temperature measuring point 207 is 200
This is because if it exceeds mm, the number of measurement points 207 becomes too small, and the widthwise distribution of the mold copper plate temperature cannot be accurately grasped.

On the other hand, the other end of the temperature measuring element 203 is connected to the zero point compensator 208, and the electromotive force signal output from the temperature measuring element 203 passes through the zero point compensator 208 and the converter 20.
9 and the converter 209 converts the electromotive force signal into a current signal, which is then converted into a current signal by the data analysis device 210.
Entered in. The measuring point 207 is sealed from the cooling water by a sealing material (not shown) so that the tip of the temperature measuring element 203 serving as the temperature measuring contact is not directly cooled by the cooling water (not shown) of the mold 204. . Also, the temperature measuring element 203
Any type of thermocouple, resistance thermometer, or the like can be used as long as it can measure temperature with an accuracy of ± 1 ° C. or more.

In the data analysis device 210, the maximum value (T _max ), the minimum value (T _min ), the average copper plate temperature (T _ave ), the maximum high and low temperature difference, Determine the maximum left-right temperature difference and the maximum value of the amount of temperature fluctuation per unit time, determine the degree of defect occurrence by comparing with the preset threshold value according to the quality grade, and determine the slab care method. . Typical values of these maximum value (T _max ), minimum value (T _min ), average copper plate temperature (T _ave ), maximum height difference, and maximum left-right temperature difference are measured at regular intervals or continuously. The maximum value (maximum value (T
_max ) and the maximum high / low temperature difference and the maximum left / right temperature difference), or the smallest value (in the case of the minimum value (T _min ) and the average copper plate temperature (T _ave )), or the measured value of the slab. Either value may be used as the average value, but in the sense of reliably detecting the surface defect of the cast slab, it is preferable to make the determination based on the largest value or the smallest value.
The temperature fluctuation amount per unit time is 5 to 20 seconds as a unit time, and the temperature fluctuation amount during this period is calculated to obtain the maximum value of the temperature fluctuation amount in the mold width direction. A value obtained by averaging the maximum values for each time may be used as the representative value of the slab, or the largest value among the maximum values for each unit time of the slab may be used as the representative value.

Further, in actual operation, the molten steel flow pattern in the mold 204 often changes with time, or three types of basic patterns 0, 1, 2 are often combined, so that the slab is cast. It is preferable to combine two or more determination methods for determining the surface defect.

As described above, according to the present invention, the quality of the slab surface is judged based on the mold copper plate temperature measured over the entire mold width. It becomes possible to accurately determine surface defects online.

In the above description, the temperature measuring elements 203 are installed in one row in the width direction of the copper plate 205 on the long side of the mold, but a plurality of rows may be installed in the casting direction. Further, in the above description, the temperature measuring element 203 is installed only on one side of the mold long side copper plate 205, but it may be installed on both mold long side copper plates 205. Further, the method of blowing Ar is not limited to the above, and it may be blown from the sliding nozzle 214 or the immersion nozzle 215.

Example 1 Using the slab continuous casting machine shown in FIG. 40, the thickness was 250 mm and the width was 1600-18.
A 00 mm slab of carbon steel was cast. The slab drawing speed is 1.2 to 1.8 m / min, the amount of Ar blown into the molten steel outflow hole is 10 Nl / min, the dipping nozzle is a mountain-shaped two-hole nozzle, and the discharge angle is 25 degrees downward. Thermocouples were used as the temperature measuring elements, and were arranged at a position 50 mm below the meniscus and symmetrically at intervals of 65 mm with the immersion nozzle as the center.

The cast slab was rolled into a cold rolled coil and the surface defects of the cold rolled coil were visually inspected. FIG. 41 shows the results of the investigation, in which the horizontal axis represents the maximum value (T _max ) of the temperature of the copper plate in the mold, and the vertical axis represents the number of surface defects per coil of the cold rolled coil. In this case, the maximum value of the mold copper plate temperature on the horizontal axis (T _max) is the width direction temperature distribution was measured every 10 seconds in slab corresponding to each coil, each of the maximum value of the measuring time the (T _max) A value obtained by measuring and averaging these maximum values (T _max ) is displayed as a representative value. As shown in FIG. 41, it was found that each plot was along a straight line rising to the right.

As described above, the degree of the surface defect of the cold rolled coil can be predicted from the maximum value (T _max ) of the temperature distribution in the mold width direction, and by setting the threshold value depending on the use and grade of the cold rolled coil, no maintenance It is possible to judge the maintenance. Incidentally, in the case of FIG. 41, the threshold value can be set to 160 ° C., and when the maximum value (T _max ) is less than 160 ° C., “no maintenance” can be performed, and when the maximum value (T _max ) is 160 ° C. or more, “care” can be performed. . Incidentally, the surface defects even higher maximum value (T _{ma x)} is that it may not occur, since the originally 1 is very small number of defects per coil, in this case there is no entrainment of stochastically mold powder I can say.

Example 2 Using the slab continuous casting machine shown in FIG. 40, a slab of carbon steel having a thickness of 250 mm and a width of 2000 mm was cast. Cast strip drawing speed is 1.2m /
min, the amount of Ar blown into the molten steel outflow hole is 10 Nl
/ Min, the immersion nozzle is a mountain-shaped two-hole nozzle, and its discharge angle is 25 degrees downward. Thermocouples were used as the temperature measuring elements, and were arranged at a position 50 mm below the meniscus and symmetrically at intervals of 65 mm with the immersion nozzle as the center. Under this casting condition, the pattern of the mold copper plate temperature was almost pattern 1 although it fluctuated with time.

The surface of the cast slab was visually inspected using a color check method to investigate blow defects and slurries. FIG. 42 shows the results of the investigation, in which the horizontal axis represents the minimum value of the mold copper plate temperature (T _min ) and the vertical axis represents the total number of blow defects and norokami per unit area of the slab surface. is there. In this case, the minimum value (T _min ) of the mold copper plate temperature on the horizontal axis is obtained by measuring the minimum value (T _min ) at each measurement time from the widthwise temperature distribution measured every 10 seconds in each slab. A value obtained by averaging the minimum values (T _min ) of is displayed as a representative value. As shown in FIG. 42, it was found that as the minimum value of temperature (T _min ) became lower, blow flaws and slurries increased. In this way, the degree of slab surface defects can be predicted from the minimum value (T _min ) of the temperature distribution in the mold width direction, and by setting the threshold value according to the application and grade, it is possible to make a judgment of no maintenance-care. Incidentally, in the case of FIG. 42, the threshold value can be set to 120 ° C., and when the minimum value (T _min ) is 120 ° C. or less, “care” can be performed, and when it exceeds 120 ° C., “no maintenance” can be performed. ..

Example 3 Using the slab continuous casting machine shown in FIG. 40, the thickness was 250 mm and the width was 1600-18.
A 00 mm slab of carbon steel was cast. The slab drawing speed is 1.6 to 1.8 m / min, the amount of Ar blown into the molten steel outflow hole is 10 Nl / min, the dipping nozzle is a chevron 2-hole nozzle, and the discharge angle is 25 degrees downward. Thermocouples were used as the temperature measuring elements, and were arranged at a position 50 mm below the meniscus and symmetrically at intervals of 65 mm with the immersion nozzle as the center. Under this casting condition, the pattern of the mold copper plate temperature was almost pattern 2 although it fluctuated with time.

The cast slab was rolled into a cold rolled coil, and the surface defects of the cold rolled coil were visually inspected. FIG. 43 shows the results of the investigation, in which the horizontal axis represents the maximum difference in temperature and the vertical axis represents the maximum difference in temperature between the right and left, and the number of surface defects generated per coil of the cold rolled coil is displayed. in this case,
The maximum vertical temperature difference on the horizontal axis and the maximum horizontal temperature difference on the vertical axis are calculated from the temperature distribution in the width direction measured every 10 seconds in the slab corresponding to each coil. The difference is measured, and the average value of these measured values is displayed as a representative value. As shown in FIG. 43, each plot was along a straight line rising to the right, and it was found that the number of defects in the cold-rolled coil increased as it came to the upper right plot.

As described above, the degree of surface defect of the cold-rolled coil can be predicted from the maximum height difference and the maximum left-right temperature difference of the temperature distribution in the mold width direction, and by setting the threshold value according to the use and grade of the cold-rolled coil, No maintenance-It is possible to judge the maintenance. Incidentally, in the case of FIG. 43, the threshold value of the maximum temperature difference of 10 ° C. and the threshold value of the maximum left-right temperature difference of 2 ° C. can be set as a boundary between no maintenance and care.

Example 4 Using the slab continuous casting machine shown in FIG. 40, the thickness is 250 mm and the width is 1800 to 21.
A 00 mm slab of carbon steel was cast. The slab drawing speed is 1.0 to 1.6 m / min, the amount of Ar blown into the molten steel outflow hole is 10 Nl / min, the dipping nozzle is a mountain-shaped two-hole nozzle, and the discharge angle is 25 degrees downward. Thermocouples were used as the temperature measuring elements, and were arranged at a position 50 mm below the meniscus and symmetrically at intervals of 65 mm with the immersion nozzle as the center. Under this casting condition, the pattern of the mold copper plate temperature was almost pattern 1 although it fluctuated with time.

The surface of the cast slab was visually inspected using a color check method to investigate blow defects and slurries. FIG. 44 shows the results of the investigation, in which the horizontal axis represents the average copper plate temperature (T _ave ) of the mold copper plate temperature, and the vertical axis represents the maximum temperature difference, and the number of blow defects and the number of burrows per unit area of the slab are shown. It is displayed by the total number. In this case, the average copper plate temperature (T _ave ) on the horizontal axis and the maximum height difference on the vertical axis are calculated from the widthwise temperature distribution measured every 10 seconds in each slab, and the average copper plate temperature (T
_ave ) and the maximum high and low temperature difference are measured, and the average value of these measured values is displayed as a representative value. As shown in FIG. 44, it was found that blow defects and slurries increased in the lower left plot.

As described above, the degree of surface defects of the slab can be predicted from the average copper plate temperature (T _ave ) of the temperature distribution in the mold width direction and the maximum difference in temperature, and by setting the threshold value depending on the application and grade, no maintenance is required. -It is possible to judge the maintenance. Incidentally, in the case of FIG. 44, the threshold of the average copper plate temperature (T _ave ) can be set to 180 ° C. and the threshold of the maximum temperature difference can be set to 15 ° C., which can be a boundary between no maintenance and maintenance.

Example 5 Using the slab continuous casting machine shown in FIG. 40, carbon steel having a thickness of 250 mm and a width of 1600 mm was continuously cast for 5 heats. Slab drawing speed is 1.8
m / min, the amount of Ar blown into the molten steel outflow hole is 10
Nl / min, the dipping nozzle is a mountain-shaped two-hole nozzle, and its discharge angle is 25 degrees downward. Thermocouples were used as the temperature measuring elements, and were arranged at a position 50 mm below the meniscus and symmetrically at intervals of 65 mm with the immersion nozzle as the center. The number of temperature measuring elements is 25.

First, the molten steel flow velocity at the meniscus was measured by the method of immersing the immersion rod in the meniscus and measuring the molten steel flow velocity from the force received by the immersion rod, and the long-period flow fluctuation of the molten steel in the mold was investigated. . As a result, it was found that the long-term flow fluctuation was about 30 seconds. Therefore, the unit time was set to 10 seconds and the fluctuation amount of the mold copper plate temperature was measured. FIG. 45 shows an example of the measured values of the mold copper plate temperature at time t and 10 seconds before time t. In FIG. 45, ● indicates temperature at time t, and ○ indicates 10 at time t.
It is the temperature before 2 seconds.

As shown in FIG. 45, during this period, the temperature of the mold copper plate increased in 10 seconds on the left side of the mold centering on the immersion nozzle, and conversely decreased on the right side. In this case, the maximum value of the temperature fluctuation amount per unit time is the value measured by the thermocouple of No. 6 on the right side in the mold width direction. The value obtained by dividing this temperature difference by 10 seconds per unit time was taken as the maximum value of the temperature fluctuation amount per unit time.

Then, the cast slab was rolled into a cold rolled coil, and the surface defects of the cold rolled coil were visually inspected. FIG. 46 shows a coil of 35 cold-rolled coils corresponding to the slabs in the casting order, with the vertical axis representing the maximum value of the temperature fluctuations measured at intervals of 10 seconds in the slabs corresponding to the respective coils. It is the figure displayed in numerical order. In FIG. 46, the coils corresponding to the bottom slab and the top slab are excluded from the cast slab, and the direction from the smaller coil number to the larger coil number is the casting direction.

No. 1 and N shaded in FIG.
o.5, No.8, No.12, No.20, No.21, No.2
Surface defects were found in the coils of No. 3, No. 30, and No. 31. In these coils, the maximum value of the temperature fluctuation amount exceeded 1.0 ° C./sec somewhere in the cast slab. And, in the No. 1, No. 21, No. 30, and No. 31 coils in which the maximum value of the temperature fluctuation exceeds 1.5 ° C./sec, three or more surface defects occur per coil and the yield decreases. It was the cause.

As described above, the degree of surface defect of the cold-rolled coil can be predicted from the maximum value of the temperature fluctuation amount, and by setting the threshold value according to the application and grade of the cold-rolled coil, it is possible to judge whether maintenance is not performed or maintenance is performed. Become. Incidentally, in the case of FIG. 46, the threshold value is set to 1.0 ° C./sec, and when the maximum value of the temperature fluctuation amount is 1.0 ° C./sec or less, it is set to “no maintenance” and 1.0 ° C./sec is set. If it exceeds, it can be treated as "care."

[Example 6] Slab continuous casting shown in Fig. 40
Using a manufacturing machine, the thickness is 250 mm and the width is 1250 to 19
A slab of carbon steel having a diameter of 00 mm and a composition of CaO: 33.
6 wt%, SiO ₂: 39.1 wt%, Al₂O₃: 5.
0 wt%, Na₂O: 3.4 wt%, F: 7.6 wt
%, MgO: 6.9 wt%, viscosity at 1300 ° C.
Casting using mold powder with a value of 0.35 Pa · s
I made it. Cast strip drawing speed is 0.78 to 1.82 m / mi
n, the amount of Ar blown into the molten steel outflow hole is 10 Nl / m
in, the dipping nozzle is a mountain-shaped two-hole nozzle, its discharge angle
Is 25 degrees downward. A thermocouple is used as a temperature measuring element,
Center the immersion nozzle at a position 50 mm below the meniscus
Are symmetrically arranged at intervals of 65 mm.

The cast slab was rolled into a cold-rolled coil and visually inspected for a shaving-like surface defect which is considered to be caused by slag in the cold-rolled coil, and the average copper plate temperature (T
_ave ). Figure 47 shows the results of the survey.
It is the figure which showed the relationship between the cast strip drawing speed and the average copper sheet temperature (T _ave ) according to the surface defect occurrence rate of the cold rolled coil. In this case, the average copper plate temperature (T _ave ) on the vertical axis is obtained by measuring the average copper plate temperature (T _ave ) at each measurement time from the widthwise temperature distribution measured every 10 seconds in each slab. The average value is shown as a representative value.

In FIG. 47, the mark ∘ indicates the average copper plate temperature (T _ave ) of the slab corresponding to the coil in which no whisker-like defect caused by Norokami was recognized. Dashed line penetrating the ○ mark average copper plate temperature of ○ mark group was determined by the minimum square method (T _ave) is a curve of the average copper plate temperature of a typical mold width direction Temperature at the slab drawing speed (T _ave) Becomes All circles were distributed in the range of ± 25 ° C of this curve. Further, in FIG. 47, a temperature curve shifted by 25 ° C. to the low temperature side is shown by a solid line.

On the other hand, the average copper plate temperature (T _ave ) of the slab corresponding to the coil in which the whisker-like defects due to Nokami were found is shown by Δ in FIG. 47. It was found that these Δ marks were lower than the above-mentioned solid line, that is, lower than the typical average copper plate temperature (T _ave ) at the slab drawing speed by 25 ° C. or more.

Thus, the average copper plate temperature (T _ave ) of the temperature distribution in the mold width direction was monitored, and the monitored value was compared with the typical average copper plate temperature (T _ave ) at the slab drawing speed. By doing so, the degree of surface defects of the cast piece can be predicted. Then, by setting a threshold value according to the use and grade, it is possible to make a judgment of no maintenance-maintenance. By the way, the fourth
In the case of FIG. 7, the threshold value of the difference between the average copper plate temperatures (T _ave ) can be set to 25 ° C., which can be used as a boundary between no maintenance and maintenance.

Best Mode 4 First, explanations will be given from the results of studying fluctuations in the air gap thickness between the mold powder layer and the mold copper plate and noise caused by fluctuations in the mold powder layer thickness from the measured values of the mold copper plate temperature. To do.

As a factor that affects the temperature of the mold copper plate,
Slab drawing speed, mold cooling water temperature, mold copper plate thickness, molten steel temperature in mold, molten steel flow velocity along solidified shell surface, air gap thickness between mold powder layer and mold copper plate, mold powder layer thickness, There are seven factors. However, among these seven factors, the influence of the cast strip drawing speed is constant as long as the mold width direction at a certain moment is considered, and can be ignored. Further, since the cooling water temperature and the thickness of the copper mold plate do not change significantly during the casting period, these influences can be ignored. There is little change in the molten steel temperature in the mold during the casting, and this influence can be ignored. The influence of the thickness of the mold powder layer and the influence of the thickness of the air gap are large, and it is necessary to remove these fluctuations when evaluating the molten steel flow rate.

The actual mold copper plate temperature is a combination of fluctuations in the flow velocity profile, fluctuations in the solidified shell thickness, and fluctuations in the mold powder layer thickness. Even if the spatial resolution of the temperature distribution is decreased by sparsely disposing the temperature measuring elements in the mold width direction in order to avoid the influence of the fluctuation of the solidified shell thickness and the fluctuation of the mold powder layer thickness, it is possible to measure it by accident. When the arrangement interval of the temperature elements becomes close to an integral multiple of the spatial fluctuation wavelength of the fluctuation of the solidified shell thickness and the fluctuation of the mold powder layer thickness, the mold copper plate temperature fluctuates greatly, which is large in the estimated value of the molten steel flow condition. There is an error.

Therefore, the present inventors investigated the variation intervals of the mold powder layer thickness and the air gap thickness from the variation of the solidified shell thickness of the cast piece by the test continuous casting machine or the actual machine. It is known that the variation of the solidified shell thickness greatly affects the variation of the mold powder layer thickness and the air gap thickness. As a result, it was found that the variation intervals of the mold powder layer thickness and the air gap thickness were several tens mm.

On the other hand, one end of the refractory rod was immersed in a meniscus, and the force applied to the refractory rod by the molten steel flow was measured by a load cell to measure the molten steel flow velocity. The flow velocity profile of the molten steel along the line was measured, and the spatial variation wavelength of the flow velocity profile of the molten steel in the mold was investigated. The measurement of this flow velocity profile is
The combination of the slab withdrawal speed and the slab width can be set to levels 1-3
Implemented after changing to standard. Table 5 shows the casting conditions of each level. Further, the measurement results of the molten steel flow velocity profile near the meniscus at levels 1 to 3 are shown in FIGS.
48 to 50, the value of "positive" in the meniscus molten steel flow velocity on the vertical axis represents the flow from the mold short side to the dipping nozzle side, and the value of "negative" represents the flow in the opposite direction. It represents.

[0156]

[Table 5]

As shown in FIGS. 48 to 50, the wavelength of the molten steel flow velocity profile near the meniscus along the mold width direction, that is, the wavelength of the molten steel flow velocity is 17 at level 1.
50mm, 800mm for Level 2, 880m for Level 3
It is understood that m is about 800 to 1800 mm.

As described above, it was found that the space change interval of molten steel flow was several hundred mm to several thousand mm, while the mold powder layer thickness and air gap thickness variation intervals were several tens mm. Therefore, by utilizing the fact that the space variation interval of the molten steel flow is significantly larger than the variation interval of the mold powder layer thickness and the air gap thickness, it was decided to remove the variation component of the mold powder layer thickness and the air gap thickness.

That is, the measured distribution of the temperature of the mold copper plate in the width direction has a fluctuation pitch of a heat removal amount of several tens of mm and a fluctuation pitch of several hundred mm to several thousand mm due to molten steel flow.
Only the variation of the mold copper plate temperature due to the molten steel flow remains in the temperature distribution after removing the variation of several tens of mm pitch. Therefore, if you want to remove at least small fluctuations of 100 mm or less due to the thickness of the mold powder layer or air gap thickness and evaluate large fluctuations over the entire mold, try to eliminate fluctuation wavelengths of 100 mm or less, or even at the maximum wavelength. A low-pass filter process is performed so as to remove the variable wavelength of ½ or less of the template width.

Here, f is the spatial frequency of the molten steel flow, and L is the fluctuation wavelength of the molten steel flow, and this fluctuation wavelength L (m
m), the spatial frequency f of molten steel flow is f = 1 / L (m
As defined by m ⁻¹ ), removing the fluctuation wavelength of 100 mm or less makes the cutoff spatial frequency fc less than 0.01. Similarly, assuming that the mold width is W (mm), removing the fluctuating wavelength of 1/2 or less of the mold width W makes the cutoff spatial frequency fc larger than 2 / W.

As described above, according to the present invention, the temperature of the mold copper plate is measured by a plurality of temperature measuring elements installed on the back surface of the mold copper plate for continuous casting in the direction orthogonal to the slab drawing direction to determine the cutoff spatial frequency fc. Greater than 2 / W and 0.0
Since the low-pass filter treatment is performed in the range smaller than 1, noise due to variations in the mold powder layer thickness and the air gap thickness can be removed. And, because the molten steel flow condition in the mold is estimated based on the temperature distribution of the low-pass filtered mold copper plate temperature, fluctuations in the mold copper plate temperature due to fluctuations in the solidified shell thickness and fluctuations in the mold powder layer thickness are eliminated. Therefore, the flow state of the molten steel in the mold can be accurately detected.

The width of the mold is finite, and the influence of the drop in the measured temperature at the end points during the low-pass filtering cannot be ignored. Therefore, it is a very effective method to use a finite number of data to perform a low-pass filter process based on the data series that is obtained by folding and expanding the data at the end points of the mold width on both sides. The evaluation accuracy of the temperature distribution is also improved. Especially when the discharge flow rate from the immersion nozzle is high, the discharge flow collides with the copper plate on the shorter side of the mold and branches up and down, and the branched upward flow flows in the meniscus from the shorter side of the mold toward the immersion nozzle side. Change direction. Therefore, as a characteristic of the temperature distribution of the copper plate, a high temperature is observed on the short side of the mold. In order to accurately capture this feature, it is necessary to effectively remove the temperature drop at the end point of the mold width.

As an example of the low-pass filter treatment, there is a spatial moving average, and this method is simple, and it depends on the variation of the air gap thickness between the mold powder layer and the mold copper plate or the mold powder layer thickness from the measured value of the mold copper plate temperature. It is preferably used as a means for removing noise.

The spatial moving average is i = 1 in one direction from one end to the other end at the temperature measurement point of the mold copper plate temperature,
2, ..., K (K is the temperature measuring point at the other end), the temperature Tn (ave) after the spatial moving average is calculated as follows for the temperature Tn at the temperature measuring point where i = N. It is defined by the equation (14). However, in the equation (14), L = (M-1)
/ 2, and the average number M is an odd number.

[0165]

[Equation 1]

By the way, in general, an arbitrary continuous function can be expressed as a set of sine waves represented by the following expression (15) by the definition of Fourier transform.

[0167]

[Equation 2]

The cutoff spatial frequency fc has a gain of 1 / √
Since the frequency is 2, the cutoff spatial frequency fc can be expressed by the following expression (16) using the expression (15). (1 / 2πfc L) × [(2-2cos 2πfc L) ^1/2 = 1 / √2 (16) From equation (16), fc × L≈0.443 is obtained. Then, when the number of points to be averaged is M and the installation interval between adjacent temperature measuring elements is Δh, equation (17) is derived. fc × L≈0.443 = fc × M × Δh (17)

Here, in the case where M is 3 which is the minimum, in order to cut off a wave whose fluctuation pitch is shorter than 100 mm, the installation interval Δh between adjacent temperature measuring elements must satisfy the following expression (18). Yes, and in the case where M is 3 which is the minimum, in order to block a wave whose fluctuation pitch is shorter than 1/2 of the mold width W,
The installation interval Δh between adjacent temperature measuring elements needs to satisfy the following expression (19). Δh = 0.443 / [(1/100) × 3] = 44.3 / 3 …… (18) Δh = 0.443 / [(2 / W) × 3] ＝ 0.443W / 6 …… (19) Therefore, normal operation Then, if the installation interval Δh (mm) between the adjacent temperature measuring elements is set within the range of the following formula (20), the target wave can be removed. 44.3 / 3 <Δh <0.443W / 6 …… (20)

The average number M does not necessarily have to be 3, and can be determined as follows. The attenuation R of the sinusoidal wave due to the spatial moving average is expressed by the following equation (21). In the equation (21), π is the circular constant, f is the spatial frequency of a sinusoidal wave, τ = M / fs, and fs is the spatial frequency of the embedding interval of the temperature measuring element in the mold width direction. Is represented by a value obtained by dividing the reference mold width by the installation interval of the temperature measuring element.

R = (1 / 2πfτ) × [2−2cos (2πfτ)] ^1/2 (21) By changing the averaging number M, the attenuation amount M of each frequency f of the sinusoidal wave can be calculated. The amount of attenuation R in the frequency range of the molten steel flow velocity profile to be measured and calculated by the equation (21) becomes as small as possible, and to the temperature of the mold copper plate caused by the fluctuation of the solidified shell thickness to be removed and the fluctuation of the mold powder layer thickness. It is sufficient to adopt the averaged number M in which the frequency range of fluctuation of is sufficiently attenuated. As described above, by performing the spatial moving average with the averaged number M as an appropriate value, it is possible to remove the fluctuations of the solidified shell thickness and the mold powder layer thickness, which are shorter than the wavelength of the molten steel flow velocity profile.
Sufficient damping means that the value after damping is 1/1 of the value before damping.
The state is about 0, and when the attenuation amount M is displayed in dB, the amount of attenuation M is about −10 dB.

As described above, the variation of the mold copper plate temperature during casting is caused by the variation of molten steel flow rate, the variation of mold powder layer thickness, and the variation of air gap thickness. The low-pass filter treatment described above removes noise caused by variations in the thickness of the mold powder layer and the thickness of the air gap that affect the mold copper plate temperature. Therefore, the influence of the mold powder layer thickness and the air gap thickness on the mold copper plate temperature in the mold width direction can be obtained by subtracting the value subjected to the low pass filter from the measured value of the mold copper plate temperature.

In continuous casting, when the heat removal inside the mold becomes uneven in the width direction of the mold due to variations in the thickness of the mold powder layer and the air gap thickness, the thickness of the solidified shell in the width direction of the mold becomes uneven, and Not only does vertical cracking occur to deteriorate the quality of the slab, but when the thickness of the solidified shell becomes extremely thin, so-called breakout occurs in which molten steel flows out under the static pressure of molten steel just below the mold.

As described above, if the low-pass filtered value is subtracted from the measured value of the mold copper plate temperature,
The non-uniformity of heat removal in the mold width direction can be grasped online, and by feeding back the grasped result to the casting conditions, it is possible to improve the quality of the slab and ensure the stability of casting.

Next, the result of studying the optimization of the sampling interval for data collection will be described. A computer is usually used to capture the temperature distribution of the mold copper plate based on the temperature measurement values of multiple temperature measuring elements installed on the backside of the mold copper plate, and to infer the molten steel flow condition from the obtained mold copper plate temperature distribution. It is common that this is done. However, due to the structure of the device, computer data processing must use discrete data that is not continuous in time.

Therefore, the inventors of the present invention used a magnetic field generator of a moving magnetic field type installed on the back surface of the copper plate on the long side of the mold in the continuous casting machine and the temperature measuring device for the copper plate of the mold used in the examples to be described later. In order to detect the change in the molten steel flow condition in the mold without omission by investigating how long the change of the molten steel flow is completed by intentionally changing the molten steel flow, in order to detect the change of the molten steel flow condition in the mold without omission, We examined how much discrete time intervals are allowed when collecting data from the temperature sensor.

The investigation was conducted as follows. Slab thickness:
220 mm, slab width: 1875 mm, slab withdrawal speed:
1.6m / min, Ar blowing amount 1 into the immersion nozzle
Under the casting condition of 3 Nl / min, the magnetic flux density of the moving magnetic field type magnetic field generator is increased stepwise from 0.03 tesla to 0.05 tesla, and after a certain period of time, it is reduced stepwise to 0.03 tesla again. The change with time of the temperature of the copper plate on the long side of the mold was investigated. The survey results are shown in FIG. 51st
The figure shows 731.5 on the right side from the widthwise center of the copper plate on the long side of the mold.
mm, 798 mm, 864.5 mm, and 86 to the left
It is a figure which shows the time-dependent change of the copper plate length side of a casting mold in the position 4.5 mm apart. In each case, it was found that the transition period of the temperature change of the copper plate on the long side of the mold when the magnetic flux density was changed was about 60 seconds.

The same investigation was conducted under various casting conditions, the transition period of the temperature change of the copper plate on the long side of the mold was determined, and summarized in a histogram in FIG. From FIG. 52, it was found that the transition period was distributed between 60 seconds and 120 seconds. Therefore, if the discrete time interval when collecting the temperature measurement values by the temperature measuring element is set to 60 seconds or less, it is possible to detect the change in the molten steel flow state in the mold that affects the quality without omission.

As described above, in the present invention, when collecting the temperature measurement value of the temperature measuring element installed on the mold copper plate,
Intermittently sampled at intervals of 60 seconds or less, and the molten steel flow condition in the mold is estimated based on the mold copper plate temperature sampled at this interval. It can be detected accurately.

The present invention will be described below with reference to the drawings. FIG. 53 is a schematic front sectional view of a continuous casting machine mold part to which the present invention is applied. As shown in FIG. 53, a mold 30 composed of opposed mold long side copper plates 305 and opposed mold short side copper plates 306 installed inside the mold long side copper plates 305.
4, a tundish 313 is arranged above.
An upper nozzle 318 is provided at the bottom of the tundish 313. The upper nozzle 318 is connected to the fixing plate 319,
A sliding nozzle 314 including a sliding plate 320 and a rectifying nozzle 321 is arranged, and a dipping nozzle 315 is arranged on the lower surface side of the sliding nozzle 314 to form a molten steel outflow hole 322 from the tundish 313 to the mold 304. To be done.

From the ladle (not shown) to the tundish 31
The molten steel 301 injected into the No. 3 via the molten steel outflow hole 322 is provided in the lower part of the immersion nozzle 315, and from the discharge hole 316 immersed in the molten steel 301 in the mold 304,
Direct the discharge flow 317 toward the copper plate 306 on the short side of the mold 304
Injected inside. Then, the molten steel 301 is cooled in the mold 304 to form the solidified shell 302, and is drawn below the mold 304 to become a cast piece. Mold powder 312 is added on the meniscus 311 in the mold 304.

The upper nozzle 318 is made of porous brick,
In order to prevent alumina from adhering to the wall surface of the molten steel outflow hole 322, Ar is blown into the molten steel outflow hole 322 from the upper nozzle 318 via an Ar introduction pipe (not shown) connected to the upper nozzle 318. Ar blown is molten steel 301
At the same time, it passes through the immersion nozzle 315, flows into the mold 304 through the discharge hole 316, passes through the molten steel 301 in the mold 304, floats on the meniscus 311 and penetrates the mold powder 312 on the meniscus 311 to reach the atmosphere.

At the position on the back surface of the copper plate 305 on the long side of the mold, below the meniscus 311 in the drawing direction of the slab, a plurality of copper plates 305 on the long side of the mold are formed on a straight line orthogonal to the drawing direction of the slab. A hole is provided and serves as a measurement point 307 for measuring the copper plate temperature of the copper plate 305 on the long side of the mold. At each measurement point 307, a temperature measuring element 303 is arranged with its tip in contact with the copper plate 305 on the long side of the mold, and the temperature of the copper plate on the long side of the mold corresponding to the entire width of the cast piece can be measured. When the mold copper plate temperature is low-pass filtered, the adjacent measuring points 3
The interval of 07 is 44.3 / 3 = 14.8 mm or more, 0.4
It is necessary to set the range to 43 × [mold width (mm)] / 6 or less. The distance from the meniscus 311 to the measuring point 307 is preferably 10 to 135 mm apart in the slab drawing direction. In the range of less than 10 mm from the meniscus 311, the temperature of the mold copper plate rises and falls due to the fluctuation of the meniscus 311 during casting, so it is not possible to accurately grasp the change in the mold copper plate temperature due to molten steel flow, and the meniscus 311
At a position below 11 mm and over 135 mm, the amount of change in the copper plate temperature decreases due to the development of the solidification shell 302,
This is because the measurement accuracy cannot be expected. Furthermore,
The distance from the molten steel side surface of the copper plate 305 on the long side of the mold to the tip of the temperature measuring element 303 is preferably 16 mm or less in order to accurately grasp the change in molten steel flow rate from moment to moment.

On the other hand, the other end of the temperature measuring element 303 is connected to the zero point compensator 308, and the electromotive force signal output from the temperature measuring element 303 passes through the zero point compensator 308 and the converter 30.
9 and the converter 309 converts the electromotive force signal into a current signal, which is then converted into a current signal by the data analysis device 310.
Entered in. The data analysis device 310 is provided with a low-pass filter process, for example, a function of calculating a spatial moving average by the above-mentioned equation (20). The measuring point 307 is sealed from the cooling water by a sealing material (not shown) so that the tip of the temperature measuring element 303 serving as the temperature measuring contact is not directly cooled by the cooling water (not shown) of the mold 304. . The temperature measuring element 303 may be of any type as long as it can measure the temperature with an accuracy of ± 1 ° C. or higher among thermocouples, resistance temperature measuring elements, and the like.

The data analysis device 310 intermittently reads the temperature data of the copper plate on the long side of the mold transmitted from the converter 309 at intervals of 60 seconds or less, and spatially moves the read data at each measurement point 307 by the equation (20). On average, the spatially moving average temperature Tn (ave) distribution in the mold width direction is displayed on a monitor (not shown), or the molten steel flow pattern defined in advance from the temperature distribution of the copper plate on the long side of the mold is displayed. In addition, (2
As for the average number M in the equation (0), an optimum value is input in advance in consideration of the frequency of the molten steel flow velocity profile.

In the present invention, the molten steel 3 in the mold is thus manufactured.
Since the flow condition of 01 is detected, it is possible to remove the noise of the fluctuation of the solidified shell thickness and the mold powder layer thickness, and the sampling interval of the data collection is optimized to detect the flow change accurately and without omission. It becomes possible. Further, when the molten steel flow pattern is controlled by feeding back from the detected molten steel flow pattern to the casting conditions such as the slab drawing speed and the amount of Ar blown into the molten steel outflow hole 322,
Since the detected information is accurate, quick and appropriate feedback control can be performed.

[0187] In the above description, the temperature measuring element 303 is installed in one row in the width direction of the copper plate 305 on the long side of the mold on one side. It may be installed on the copper plate 305. Also, the mold short side copper plate 306
Although the temperature measuring element 303 is not installed in the mold, it may be installed in the copper plate 306 on the short side of the mold. Furthermore, the method of blowing Ar is not limited to the above, and may be blown from the sliding nozzle 314 or the immersion nozzle 315.

[Example 1] An example in which the flow detection of the molten steel in the mold was carried out using the slab continuous casting machine shown in Fig. 53 will be described below. The continuous casting machine is a vertical bending mold having a vertical portion of 3 m, and can cast a slab of maximum 2100 mm. Table 6 shows the specifications of the continuous casting machine used.

Alumel chromel (JI
Using S thermocouple K), the distance from the molten steel side surface of the copper plate on the long side of the mold to the thermocouple tip (temperature measuring contact) is 13 mm, the distance between adjacent thermocouples is 66.5 mm, and the distance from the meniscus is 50 mm. As a result, a thermocouple was embedded over a length of 2100 mm in the mold width direction. And thickness 220mm, width 1
700 mm slab, cast strip drawing speed 2.1 m / mi
Casting was performed under the casting conditions of n and Ar blowing amount of 10 Nl / min.

[0190]

[Table 6]

FIG. 54 shows a temperature distribution in the width direction of the mold based on raw data of the copper plate temperature on the long side of the mold collected under these casting conditions. The temperature distribution is composed of short-wavelength fluctuations that are thought to be caused by fluctuations in the solidified shell thickness and fluctuations in the mold powder layer thickness. Incidentally, the horizontal axis of FIG. 54 is the position in the mold width direction, the central "0 mm" position is the center position in the mold width direction, the position of the immersion nozzle, the negative sign represents the left side in the mold width direction, The plus sign represents the right side in the mold width direction (hereinafter, the position in the mold width direction is indicated by the same display method).

Therefore, it was decided to apply the spatial moving average to the temperature distribution shown in FIG. First, the average number M was determined as follows. The mold width, which is the reference when determining the spatial frequency f of the sine wave and the spatial frequency fs of the embedding interval of the temperature measuring element, is set to 2100 mm, which is the maximum width of the mold, and the average number M is 3, 5 or 3 levels. And the attenuation amount R of the sinusoidal wave was calculated. The result is shown in FIG. 55. Fifth
As shown in FIG. 5, by changing the average number M, a difference occurs in the attenuation amount R of the sinusoidal wave having a wavelength of 1000 mm or less.

In this example, it is considered that this is caused by the variation of the solidified shell thickness and the variation of the mold powder layer thickness.
A sine wave with a wavelength of about 00 mm is removed, which is considered to correspond to the flow velocity profile of molten steel 800 to 18
A sine wave with a wavelength of about 00 mm is desired to remain. From this point of view, when examining FIG. 55, it was determined that the averaging number M is 3 and the averaging number M is 3 when the attenuation amount R of the wave having a wavelength of about 200 mm is the largest. It can be seen that when the average number M is 5 and 7, the flow velocity profile of the molten steel may be greatly attenuated, which is not suitable. Therefore, the average number M is set to 3.

FIG. 56 shows a temperature distribution in the width direction of the copper plate on the long side of the mold, which is obtained by subjecting the temperature distribution shown in FIG. 54 to the spatial moving average with the average number M being 3. As shown in FIG. 56, in FIG. 56, the fluctuation of the short wavelength that was present in FIG. 54 was eliminated, and only the temperature fluctuation due to the flow velocity profile of the molten steel could be displayed.

Example 2 Using the same continuous casting machine as in Example 1, a slab having a thickness of 250 mm and a width of 1500 mm was drawn at a slab drawing speed of 2.0 m / min and an Ar blowing amount of 10 N.
Casting was performed under the casting condition of 1 / min. In this embodiment, an alumel chromel (JIS thermocouple K) is used as the temperature measuring element, and the distance from the molten steel side surface of the copper plate on the long side of the mold to the tip of the thermocouple (temperature measuring contact) is 13 mm. 50mm, the distance from the meniscus is 50mm,
A thermocouple was embedded over the entire surface in the width direction of the mold.

FIG. 57 shows raw data of the temperature distribution of the copper plate measured during casting at this time. This raw data represents a variation of 100 mm wavelength or more, which is twice the embedding interval. A spatial moving average was used as a low-pass filter. 58 to 60 show temperature distributions treated with the averaged number M = 3, 7, and 9. For the average number M = 3,
The cutoff spatial frequency fc is 0.003, and the wavelength is 340.
mm. With respect to the averaged number M = 7, the spatial frequency fc to be cut off is 0.0013 and the wavelength is 790 mm. For the averaged number M = 9, the cutoff spatial frequency fc is 0.001 and the wavelength is 1015 mm.

When the low-pass filter processing is not performed, the features cannot be grasped at first glance, but when M = 3, the strong flow near the short side due to the strong discharge flow is observed as a high temperature as shown in FIG. At the same time, the floating upstream of the immersion nozzle near Ar can be observed as a high temperature near the center. When M = 7, the temperature remains high near the short side and near the center as shown in FIG. 59, but it is somewhat vague. When M = 9, the temperature distribution is almost flat as shown in FIG.
The characteristics are completely unknown. From the above, the cutoff wavelength of the filter is 100 mm to the mold width (W) / 2 (= 7
It has been found that it is preferable to perform it in the range of 50 mm).

[Embodiment 3] With the same continuous casting machine and the same casting conditions as in Embodiment 2, the thermocouple embedding interval was set to 5
It was set to 0 mm, 100 mm, and 150 mm. As the low-pass filter processing, the spatial moving average was used, and processing was performed with the minimum average number M = 3. The temperature distribution when thermocouples are embedded at intervals of 50 mm is shown in FIG.
FIG. 1 shows the temperature distribution when the thermocouples were embedded at 100 mm intervals and FIG. 62 at 150 mm intervals.

The cutoff wavelengths in the case of M = 3 corresponding to the respective embedding intervals are 340 mm, 680 mm and 1015 for the intervals 50 mm, 100 mm and 150 mm, respectively.
mm. As shown in FIG. 62, when the distance is 150 mm, the low-pass filter process results in a flat temperature distribution, and the characteristics of the temperature distribution cannot be grasped.
From these results, the thermocouple embedding interval was 0.443 /
Specified by (3 x f) mm, the maximum is 0.443 x [mold width (W)] / 6 mm (1500 mm width: 110 m
It turned out that it is good if it is within m).

Example 4 Using the same continuous casting machine and temperature measuring device as in Example 2, casting was performed under the same casting conditions as in Example 2. Data obtained by folding back the data at the template end points and using the expanded data are shown in FIG. 63, where the number of averages is M = 7 and the spatial moving average is shown in FIG. When the data was folded back, the characteristics of the raw data were well captured up to the mold edge, enabling more accurate evaluation of the temperature distribution.

[Embodiment 5] Using the same continuous casting machine and temperature measuring device as in Embodiment 1, thickness 220 mm, width 1550
mm slab, slab drawing speed 2.0m / min, Ar
Casting was performed under the casting conditions of a blowing rate of 10 Nl / min. In this example, a moving magnetic field type magnetic field generator was installed on the back surface of the copper plate on the long side of the mold, and casting was performed by applying a moving magnetic field in a direction to brake the discharge flow from the immersion nozzle.

During casting, the measured copper plate temperature on the long side of the mold was collected by a data analyzer every one second. In this embodiment, in order to change the data collection interval of the copper plate temperature on the long side of the mold, the data collected by the data analysis device is further transferred to the data collection / analysis personal computer at 1 second intervals, 5 second intervals, 10 second intervals, 60 seconds. The data was transmitted at the interval of 5 seconds and at the interval of 240 seconds. The TCP / IP procedure was used to transmit the data from the data analysis device. The data collection / analysis personal computer has a CPU clock frequency of 200 MHz and a RAM memory capacity of 128 M
It is a general-purpose product of B.

During casting, when the casting length reached 165 m, the magnetic flux density of the moving magnetic field type magnetic field generator was set to 0.12.
The temperature was gradually increased from 5 Tesla to 0.145 Tesla, and the temperature change of the copper plate on the long side of the mold at this time was monitored at the above-mentioned 5 levels of collection intervals to confirm whether there was a difference in the obtained data. . Data collection /
Data collection interval on the analysis PC is 1 second, 5 seconds, 10
The time-dependent change of the copper plate temperature on the long side of the mold is shown at intervals of 60 seconds and 240 seconds.

As shown in FIG. 64 to FIG. 68, the moving magnetic field type magnetic field is changed against the temperature change when data is collected at the shortest data collection interval of 1 second even when the data collection interval is 60 seconds. The change in the temperature of the copper plate on the long side of the mold due to the change in the magnetic flux density of the generator was able to be captured almost accurately. However, when the data collection interval was set to 240 seconds, the temperature change of the copper plate temperature on the long side of the mold became dull, and the accurate temperature change could not be captured. The data shown in FIGS. 64 to 68 is 665 to the right from the center of the copper plate on the long side of the mold in the width direction.
It is a temperature measurement value at a measurement point separated by mm.

[Embodiment 6] Using the same continuous casting machine and temperature measuring device as in Embodiment 2, thickness 250 mm, width 1400.
A slab of ~ 1800 mm with an Ar blowing amount of 10 Nl /
min, and cast at a slab drawing speed of 1.2 to 1.8 m / min. Iron sulfide was added to the mold during casting, and the solidified shell thickness at 30 points was measured on each cut surface from the distribution of sulfur on the cut surface of the cast slab, and the standard deviation (σ) was obtained.

On the other hand, the measured data of the mold copper plate temperature was spatially moving averaged with the average number M = 3, and at each measurement point,
A value (Di = Ti−Tn (ave)) obtained by subtracting the value Tn (ave) after the spatial moving average from the measured value (Ti) was obtained online. Then, as shown in the following formula (22), the average value (Do) in the mold width direction of the absolute value of this value (Di) was obtained as a representative value representing the nonuniformity of heat removal in the mold.

[0207]

[Equation 3]

FIG. 69 shows the relationship between the average value in the mold width direction (Do) obtained and the standard deviation (σ) of the solidified shell thickness obtained from the sulfur distribution. As is clear from the figure, there is a very good linear relationship between the two, and the average value (Do) in the mold width direction.
It has been found that the method accurately evaluates the non-uniformity of heat removal in the mold. If the nonuniformity of the heat removal amount is evaluated online, the nonuniformity of the resulting solidified shell thickness can be indirectly predicted.

Best Mode 5 In the present invention, the purpose is to grasp the molten steel flow condition in the mold in real time without relying on the estimation database and appropriately control the molten steel flow condition based on this information.
A sensor is needed to capture the flow of molten steel in the continuous casting mold in real time. Therefore, the present inventors installed a plurality of temperature measuring elements as sensors in the width direction of the back surface of the copper plate on the long side of the mold. The convection heat transfer coefficient between the molten steel in the mold and the solidified shell changes according to the molten steel flow in the mold, and along with this, the heat flux from the molten steel through the copper plate on the long side of the mold to the cooling water for the copper plate on the long side of the mold. Varies in size. Therefore, if the temperature of the copper plate on the long side of the mold is monitored, the flow of molten steel in the mold can be monitored. Further, since the temperature measuring element does not come into direct contact with the molten steel, it is durable and can always detect the molten steel flow velocity in the mold while the mold is mounted on the continuous casting machine.

By the way, in Japanese Unexamined Patent Publication No. 10-109145, the mold size, slab drawing speed, amount of Ar blown into the dipping nozzle, and magnetic field strength for controlling molten steel flow are set to 4.
By changing the four elements, the molten steel flow pattern in the mold can be roughly divided into three patterns A, B, and C. These four elements are the targets of the casting conditions. Measure the molten steel flow pattern in the mold in advance, and estimate the molten steel flow pattern in the mold in individual casting conditions based on this measurement result,
A method of adjusting the magnetic field strength applied to the discharge flow or the amount of Ar blown into the immersion nozzle so that the flow pattern becomes the pattern B is disclosed. The pattern A is a pattern in which the discharge flow from the dipping nozzle branches up and down after reaching the solidification shell on the short side of the mold. In the meniscus, the flow is from the short side of the mold to the dipping nozzle, and the pattern B
Is a pattern in which the discharge flow from the immersion nozzle does not reach the solidification shell on the short side of the mold and is dispersed from the discharge port to the solidification shell on the short side of the mold, and the pattern C is The pattern has an upward flow in the vicinity of the immersion nozzle. In the meniscus, the flow is from the immersion nozzle to the shorter side of the mold, and the pattern B is the best because of the amount of mold powder defects generated in the products of each pattern. I am trying.

Thus, in order to minimize the quality of the product, particularly the inclusion of inclusions in the product due to the inclusion of mold powder, it is best to set the flow pattern of the molten steel in the mold to the above pattern B. . Therefore, the inventors of the present invention have used a continuous casting machine shown in an example described later for the molten steel flow velocity in the meniscus when the molten steel flow condition in the mold becomes the pattern B, cast piece thickness: 220 mm, cast piece width: 1600m
m, slab drawing speed: 1.3 m / min, amount of Ar blown into the immersion nozzle: 10 Nl / min, immersion depth of the immersion nozzle: 260 mm. The molten steel flow velocity was measured by a method of immersing a refractory rod in a meniscus and measuring it from the deflection angle of the refractory rod due to the molten steel flow (hereinafter referred to as "immersion rod type meniscus molten steel velocity meter").

The results are shown in FIG. As shown in FIG. 70, the molten steel flow velocity distribution in the meniscus corresponding to the pattern B is substantially symmetrical with respect to the center of the mold in the width direction, and the difference in absolute value of the flow velocity in the width direction of the mold is small. I found out. In FIG. 70, the flow velocity with a positive sign on the vertical axis is the flow from the mold short side to the dipping nozzle side, and the flow velocity with a negative sign is the flow flowing in the opposite direction, and the horizontal axis is the mold width direction. Position, the central "0 mm" position is the center position in the mold width direction, and is the position of the immersion nozzle. The negative sign represents the left side in the mold width direction, and the positive sign represents the right side in the mold width direction ( Hereinafter, the position in the width direction of the mold is indicated by the same display method).

Therefore, it is considered that the temperature distribution of the copper plate on the long side of the mold at this time is flat and bilaterally symmetrical from the above-mentioned characteristic of the temperature of the copper plate for the mold to the molten steel flow. Actually, the temperature distribution in the width direction of the copper plate on the long side of the mold in the case of the pattern B has the result shown in FIG. As shown in FIG. 71, the temperature distribution in the case of pattern B was substantially symmetrical in the left and right of the mold width, and was a flat temperature distribution with a small difference between the maximum value and the minimum value. In this way, as a result of measuring the temperature distribution in the pattern B under various casting conditions, in the temperature distribution of the copper plate on the long side of the mold in the pattern B, the difference between the maximum value and the minimum value is 12
It was found that the temperature distribution was relatively flat below 0 ° C, and the difference between the copper plate temperatures at the symmetrical positions with respect to the center in the width direction of the mold was 10 ° C or lower from the viewpoint of symmetry in the left and right directions of the mold.

In the present invention, the difference between the maximum value and the minimum value of the temperature distribution in the width direction of the copper plate on the long side of the mold is set to 12 ° C. or less, and preferably the symmetrical position on the left and right sides of the copper plate on the long side of the mold is centered around the immersion nozzle. By controlling the temperature difference at 10 ° C. or less, the molten steel flow in the mold is controlled to the pattern B, and the quality of the product is improved.

In the present invention, as means for controlling the molten steel flow in this way, the magnetic field strength of the magnetic field generator, the slab drawing speed, the immersion depth of the immersion nozzle, and the A in the immersion nozzle.
It was decided to adjust any one or more of the r blowing amounts.

When the magnetic field generated by the magnetic field generator is a static magnetic field, the molten steel flow in the mold receives a braking force due to Lorentz force, and when the magnetic field generated by the magnetic field generator is a moving magnetic field, the magnetic field The molten steel in the mold is driven in the moving direction of, and the molten steel flow excited by this drives the molten steel flow in the mold. Such a magnetic field generator can instantaneously change the magnetic field strength by instantaneously changing the supplied power. Therefore, it is possible to control the molten steel flow in response to the change in the molten steel flow in the mold which is measured every moment by the temperature measuring element. Further, the magnetic field generator does not come into direct contact with the molten steel and has good durability in operation. Therefore, a magnetic field can be applied to the molten steel at all times while the mold is mounted on the continuous casting machine.

By adjusting the withdrawal speed of the slab, the speed of the discharge flow from the dipping nozzle can be adjusted, so that the flow of molten steel in the mold can be controlled. Further, when the immersion depth of the immersion nozzle is adjusted, the position where the discharge flow collides with the solidified shell on the short side moves up and down. This adjusts the distance from the collision position to the meniscus, and after the collision with the solidified shell on the short side, it is possible to adjust the degree of damping until the molten steel flow branched upwards reaches the meniscus. Therefore, the molten steel flow in the mold can be controlled. Further, Ar blown into the immersion nozzle floats near the immersion nozzle when it exits the immersion nozzle, and at that time also induces an upward flow of molten steel. Therefore, the molten steel flow in the mold can be adjusted by adjusting the amount of Ar blown. still,
In the present invention, the immersion depth of the immersion nozzle represents the distance from the upper end of the discharge hole of the immersion nozzle to the meniscus.

As described above, the molten steel flow in the mold can be controlled based on the temperature distribution of the copper plate on the long side of the mold, but the temperature of the copper plate on the long side of the mold measured by the temperature measuring element is It also changes depending on factors such as the temperature and flow rate of cooling water for use. Therefore, including these factors, by determining the molten steel flow velocity in the mold from the mold copper plate temperature using the heat transfer calculation model, after eliminating factors other than the molten steel flow velocity change factor of the mold copper plate temperature, the molten steel in the mold Flow control can be performed. The method of converting the molten steel flow velocity in the mold from the temperature of the copper plate on the long side of the mold measured by the temperature measuring element is performed as follows.

FIG. 72 is a diagram schematically showing the temperature distribution from the molten steel to the cooling water in the process of heat conduction from the molten steel in the mold to the copper plate on the long side of the mold to the cooling water for the copper plate on the long side of the mold. Is. As shown in FIG. 72, between the molten steel 401 and the cooling water 405 for the copper plate on the long side of the mold, the solidified shell 4
02, mold powder layer 403, and mold long side copper plate 4
04 heat conductors are present, and temperature measuring element 4
06 is embedded in the mold long side copper plate 404, and the mold long side copper plate 4
The temperature inside 04 is measured. In the figure, To is molten steel 4
01, T _L is the interface temperature between the solidified shell 402 and the molten steel 401, T _S is the boundary temperature between the solidified shell 402 and the mold powder layer 403, and T _P is the mold powder layer 40.
3, the surface temperature on the long side copper plate 404 side of the mold, T _mH is the surface temperature on the side of the mold powder layer 403 of the long side copper plate 404 of the mold, T _mL is the surface temperature of the cooling water 405 side of the long side copper plate 404 of the mold, and Tw is the cooling. The temperature of water 405.

In this case, the total thermal resistance obtained by combining the thermal resistances of the heat conductors from the molten steel 401 to the cooling water 405 is (23)
It is represented by a formula. However, in the equation (23), R: overall heat resistance, α: convection heat transfer coefficient between molten steel and solidified shell,
λ _S : thermal conductivity of solidified shell, λ _P : thermal conductivity of mold powder layer, λ _m : thermal conductivity of copper plate on long side of mold, h _m :
Heat transfer coefficient between mold powder layer and copper plate on long side of mold, h _W : Heat transfer coefficient between copper plate on long side of mold and cooling water,
d _S : solidified shell thickness, d _P : mold powder layer thickness, d _m : mold long side copper plate thickness. R = (1 / α) + (d _S / λ _S ) + (d _P / λ _P ) + (1 / h _m ) + (d _m / λ _m ) + (1 / h _W ) ... (23) Here The thickness (d _m ) of the copper plate on the long side of the mold and the thermal conductivity (λ _m ) of the copper plate on the long side of the mold are values that are fixed depending on the equipment.
Further, the thermal conductivity (λ _S ) of the solidified shell is a value that is fixed when the steel type is determined. Also, the thickness of the mold powder layer (d
_P ) is a numerical value that is fixed if the type of mold powder, the amplitude, frequency, and vibration waveform of mold vibration, and the slab drawing speed are determined. It is known that the thermal conductivity (λ _P ) of the mold powder layer is almost constant regardless of the type of mold powder. Further, the heat transfer coefficient (h _W ) between the copper plate on the long side of the mold and the cooling water is a numerical value which is fixed when the flow rate of the cooling water 405 and the surface roughness of the copper plate 404 on the long side of the mold are determined. Further, the heat transfer coefficient between the mold powder layer and the mold long sides copper plate (h _m) is also substantially determined constant value once the type of mold powder.

However, the convection heat transfer coefficient (α) between the molten steel and the solidified shell is a value that changes depending on the molten steel flow velocity along the surface of the solidified shell 402, and this convective heat transfer coefficient (α) is (24) ) Can be expressed by a plate approximation formula. However, in the equation (24), Nu: Nusselt number, λ
₁ : Thermal conductivity of molten steel, X ₁ : Representative length of heat transfer. α = Nu × λ ₁ / X ₁ (24) Here, the Nusselt number (Nu) is represented by the equations (25) and (26) for each velocity range of the molten steel flow velocity. However (2
In equations (5) and (26), Pr is the number of prandles,
Re: Reynolds number, U: molten steel flow velocity, Uo: transition velocity between laminar flow and turbulent flow of molten steel. Nu = 0.664 x Pr ^1/3 x Re ^4/5 (U <Uo) (25) Nu = 0.036 x Pr ^1/3 x Re ^1/2 (U≥Uo) (26)

The Prandle number (Pr) and the Reynolds number (Re) are expressed by the equations (27) and (28), respectively. However, in the equation (28), X _{2 is a} representative length of molten steel flow, and ν is a kinematic viscosity coefficient of molten steel. Pr = 0.1715 (27) Re = U × X ₂ / ν (28)

On the other hand, the heat flux from the molten steel 401 to the cooling water 405 can be expressed by the equation (29). However (29)
In the formula, Q: heat flux from molten steel to cooling water, To: molten steel temperature, Tw: cooling water temperature. Q = (To-Tw) / R (29) Further, the surface temperature of the long side copper plate 404 on the cooling water 405 side can be expressed by the equation (30). However, in the formula (30), T _{mL is} the cooling water side surface temperature of the copper plate on the long side of the mold. _{T mL = Tw + Q / h} W ... (30) Further, the mold long sides copper plate temperatures measured by the temperature measurement element 406 can be expressed by equation (31). However, in the formula (31), T is the temperature of the copper plate on the long side of the mold measured by the temperature measuring element, and d is the distance from the surface of the copper plate on the long side of the mold to the temperature measuring element. _{T = T mL + Q × (} d m -d) / λ m ... (31) Then, the (30) equation (31) by substituting the equation, the mold long sides copper plate temperature (T) in the equation (32) Represented. _{T = Tw + Q / h W} + Q × (d m -d) / λ m ... (32)

Therefore, the procedure for obtaining the molten steel flow rate (U) from the temperature (T) of the copper plate on the long side of the mold is as follows. First, the measured value of the copper plate temperature (T) on the long side of the mold by the temperature measuring element is calculated as (3
The heat flux (Q) is obtained by substituting it into the equation (2). Since all variables on the right side other than the heat flux (Q) are known in the equation (32), the heat flux (Q) can be calculated backward. Next, the heat flux (Q) is substituted into the equation (29) to obtain the total thermal resistance (R). In this case as well, all variables on the right side other than the total thermal resistance (R) are known, so the total thermal resistance (R) can be calculated backward. Then, the overall heat resistance (R) is substituted into the equation (23) to obtain the convection heat transfer coefficient (α). In this case as well, all variables on the right side other than the convection heat transfer coefficient (α) are known, so that the convection heat transfer coefficient (α) can be calculated backward. The calculated convection heat transfer coefficient (α) is substituted into the equation (24) to obtain the Nusselt number (Nu), and this Nusselt number (Nu) is substituted into the equation (25) or the equation (26) to calculate the Reynolds number (R).
e) is required. And the number of Reynolds finally obtained (Re
) Is substituted into the equation (28) to obtain the molten steel flow velocity (U).
As described above, in the present invention, a change in the copper plate temperature on the long side of the mold (T) caused by a change in the convection heat transfer coefficient (α) between the molten steel and the solidified shell due to the molten steel flow velocity (U) is captured,
The molten steel flow velocity (U) along the solidification interface is estimated.

FIG. 73 is an example in which the relationship between the molten steel flow rate and the copper plate temperature on the long side of the mold is obtained by the above principle. 7th
As shown in Fig. 3, even if the temperature of the copper plate on the long side of the mold is the same, the molten steel flow rate is significantly different depending on the slab drawing speed.
It is understood that the molten steel flow rate can be estimated from the temperature of the copper plate on the long side of the mold. Incidentally, FIG. 73 shows the molten steel flow velocity calculated from the temperature of the copper plate on the long side of the mold based on the variables shown in Table 7. It shows an example of each variable in the condition. The transition velocity (Uo) between the laminar flow and the turbulent flow of the molten steel was calculated as 0.1 m / sec, and Vc in Table 7 and FIG. 73 is the slab drawing speed.

[0226]

[Table 7]

As described above, the molten steel flow velocity in the mold can be determined from the temperature of the copper plate on the long side of the mold. Therefore, in order to confirm this principle, the inventors of the present invention arranged a plurality of temperature measuring elements along the width direction of the copper plate on the long side of the mold using the continuous casting machine described above, and mold based on the temperature of each temperature measuring element. A test was conducted to estimate the molten steel flow velocity inside and the flow velocity distribution in the width direction of the mold.
An alumel-chromel thermocouple (JIS thermocouple K) was used as the temperature measuring element, and the temperature measuring contact of the thermocouple was 50 mm below the meniscus, and the distance from the molten steel side surface of the copper plate on the long side of the mold to the tip of the thermocouple (d ) Was 13 mm, and the distance between adjacent thermocouples was 66.5 mm. This thermocouple array covers the widthwise length 2100 mm of the copper plate on the long side of the mold. The electromotive force of each thermocouple is connected to a zero compensator via a compensating lead wire, and then the electromotive force is converted into a current analog output (4 to 20 m).
It was converted to A) and input to a personal computer for data collection and analysis.

The results of measuring the temperature of the copper plate on the long side of the mold are shown in FIGS. 74 and 75. Incidentally, FIG. 74 shows the thickness of the slab: 220
mm, slab width: 1650 mm, slab withdrawal speed: 1.8
5 m / min, Ar blowing amount into the immersion nozzle: 10
Nl / min, immersion depth of immersion nozzle: 260 mm, the result of measurement under the casting conditions (casting condition 1).
Slab thickness: 220 mm, slab width: 1750 mm, slab drawing speed: 1.75 m / min, Ar into immersion nozzle
The results are measured under the casting condition (casting condition 2) in which the blowing amount is 10 Nl / min and the dipping depth of the dipping nozzle is 260 mm. In both FIGS. 74 and 75, the temperatures at both skirts in the width direction of the mold greatly drop, but these are because the short sides of the mold are in the vicinity of the large drop in temperature.

FIGS. 76 and 77 show the molten steel flow velocity obtained from the temperature of the copper plate on the long side of the mold shown in FIGS. 74 and 75 by the conversion method described above. Further, the plots of ● in FIGS. 76 and 77 are the results of measuring the molten steel flow velocity in the vicinity of the meniscus using the immersion rod type meniscus molten steel flow velocity meter under the respective casting conditions. As shown in FIGS. 76 and 77, it was found that the molten steel flow velocity estimated from the temperature of the copper plate on the long side of the mold and the molten steel flow velocity measured by the immersion rod type meniscus molten steel flow velocity meter were in good agreement. Among the variables shown in Table 7, the solidified shell thickness (d _S ) was 0.00362 m under casting condition 1 and 0.00372 m under casting condition 2.

According to this method, by appropriately setting the distance (d) from the molten steel side surface of the copper plate on the long side of the mold to the tip of the temperature measuring element, the time constant of the output change of the temperature measuring element is Sufficient to capture changes in flow velocity. According to this conversion method, when the flow pattern of the molten steel in the mold is pattern B, the difference between the maximum value and the minimum value of the flow velocity is a relatively flat velocity distribution of 0.25 m / sec or less, and in the mold width direction. From the viewpoint of left-right symmetry, the difference in flow velocity at the left-right symmetrical position with respect to the center of the mold width direction is 0.20 m / s.
It was found to be ec or less. The speed difference in the present invention means a difference in absolute value of flow velocity regardless of the flowing direction of molten steel.

In the present invention, the difference between the maximum value and the minimum value of the molten steel flow velocity distribution in the width direction of the copper plate on the long side of the mold is set to 0.25 m / sec or less. Since the molten steel flow velocity difference between the left and right symmetrical positions is controlled to be 0.20 m / sec or less, the molten steel flow in the mold is controlled to the pattern B, and the quality of the product is improved. Incidentally, the measured temperature of the portion near the copper plate on the short side of the mold is added with the cooling effect from the copper plate on the short side of the mold, so that the measured temperature becomes low. The temperature of the copper plate on the long side of the mold up to 150 mm toward the center is not monitored.

The present invention will be described below with reference to the drawings. FIG. 78 is a schematic front sectional view of a continuous casting machine showing one embodiment of the present invention, and FIG. 79 is a schematic side sectional view thereof. In FIG. 78 and FIG. 79, a mold 407 composed of a copper plate 404 on the longer side of the mold and a copper plate 408 on the shorter side of the mold installed inside the copper plate 404 on the longer side of the mold.
A tundish 423 loaded on a tundish car (not shown) is arranged at a predetermined position above the. The tundish 423 is vertically moved by an elevating device (not shown) installed in the tundish car and held at a predetermined position. This lifting device is controlled by a lifting control device 419.

A long side water box 409 is installed on the upper back surface and lower back surface of the long side copper plate 404 of the mold, and the cooling water 405 supplied from the long side water box 409 on the lower back surface is the water channel 410.
The copper plate 404 on the long side of the mold is cooled by passing through and is discharged to the water box 409 on the long side on the upper side. The thickness from the front surface of the mold long side copper plate 404 to the water channel 410, that is, the mold long side copper plate thickness is d.
_m . Although not shown, the copper plate 408 on the shorter side of the mold is also cooled in the same manner. A magnetic field generator 411 is installed on the back surface of the copper plate 404 on the long side of the mold. Magnetic field generator 411
The magnetic field generated by can be either a static magnetic field or a moving magnetic field. The magnetic field strength of the magnetic field generator 411 is controlled by the magnetic field strength controller 417. In addition, in order to facilitate the control of molten steel flow in the mold 407, the magnetic field intensity generated from the magnetic field generator 411 is set to the immersion nozzle 4
It is preferable to be able to separately adjust the right and left in the mold width direction with 25 as the boundary.

An upper nozzle 428 is provided at the bottom of the tundish 423, and a sliding nozzle 424 including a fixed plate 429, a sliding plate 430, and a rectifying nozzle 431 is arranged in connection with the upper nozzle 428, and further, The immersion nozzle 42 is provided on the lower surface side of the sliding nozzle 424.
5 is placed and the tundish 423 to the mold 407.
A molten steel outflow hole 432 is formed.

The molten steel 401 poured into the tundish 423 from a ladle (not shown) is provided under the immersion nozzle 425 via the molten steel outflow hole 432, and the mold 40
The discharge flow 427 is injected into the mold 407 from the discharge hole 426 immersed in the molten steel 401 inside the mold 7 toward the mold short side copper plate 408. Then, the molten steel 401 is cooled in the mold 407 to form the solidified shell 402, and the drawing roll 412
Thus, it is pulled out below the mold 407 to form a cast piece. At that time, the mold powder 422 is added on the meniscus 421 in the mold 407, and the mold powder 422 is melted to flow between the solidified shell 402 and the mold 407 to form the mold powder layer 403. The drawing roll 412 is controlled by a slab drawing speed control device 418.

The upper nozzle 428 is made of porous brick,
In order to prevent alumina from adhering to the wall surface of the molten steel outflow hole 432, an Ar introducing pipe (not shown) connected to the upper nozzle 428 and an Ar flow rate adjusting valve (not shown) installed in the Ar introducing pipe are used. Upper nozzle 428 through the Ar supply device
Ar is blown into the molten steel outflow hole 432 from. The blown Ar flows through the immersion nozzle 425 together with the molten steel 401, flows into the mold 407 through the discharge hole 426, floats on the meniscus 421 through the molten steel 401 in the mold 407, and the mold powder 422 on the meniscus 421. To reach the atmosphere. The Ar supply device is controlled by the Ar blowing amount control device 420.

A plurality of holes are provided on the back surface of the copper plate 404 on the long side of the mold along the width direction of the copper plate 404 on the long side of the mold, and serve as measurement points 413 for measuring the copper plate temperature of the copper plate 404 on the long side of the mold. At each measuring point 413, the temperature measuring element 406 has a distance from the molten steel side surface of the copper plate 404 on the long side of the mold to the tip of the temperature measuring element 406, and the tip is the copper plate 404 on the long side of the mold.
It is placed in contact with. At that time, it is preferable that the distance (d) be 16 mm or less in order to accurately grasp the change in molten steel flow rate every moment. Also, the meniscus 42 during casting
The distance from the meniscus 421 to the measuring point 413 is 10 mm in order not to be affected by the temperature fluctuation due to the vertical movement of
The above is preferable. Furthermore, in order to accurately grasp the temperature distribution in the mold width direction, it is preferable that the interval between adjacent measurement points 413 is 200 mm or less.

On the other hand, the other end of the temperature measuring element 406 is connected to the zero point compensator 414, and the electromotive force signal output from the temperature measuring element 406 passes through the zero point compensator 414 and the converter 41.
5, the converter 415 converts the electromotive force signal into a current signal, and the data analyzer 416 converts the current signal into a current signal.
Entered in. The data analysis device 416 is provided with a function of calculating the molten steel flow velocity from the temperature of the copper plate on the long side of the mold.
The output of the data analysis device 416 is the magnetic field strength control device 41.
7, slab drawing speed control device 418, lifting control device 41
9 and the Ar blowing amount control device 420.
The tip of the temperature measuring element 406, which serves as a temperature measuring contact, is connected to the cooling water 40.
The measuring point 413 is sealed from the cooling water 405 by a sealing material (not shown) so that the measuring point 413 is not directly cooled by the cooling water. Further, the temperature measuring element 406 may be of any type as long as it can measure temperature with an accuracy of ± 1 ° C. or higher among thermocouples, resistance temperature measuring elements and the like.

In the continuous casting equipment having such a structure,
The flow of molten steel in the mold is controlled as follows. The data analysis device 416 captures the maximum and minimum values of the temperature from time to time from the temperature distribution of the copper plate on the long side of the mold in the width direction of the mold, and at the same time, symmetrically in the width direction of the copper plate 4 on the long side of the mold with the immersion nozzle 425 as the center. Capture the temperature difference at the position. Then, the difference between the captured maximum value and the minimum value is 12 ° C. or less, and more preferably, the temperature difference at the symmetrical positions in the lateral direction of the copper plate 404 on the long side of the mold is 10 ° C. or less. A control signal is transmitted to any one or two or more of the magnetic field strength control device 417, the slab drawing speed control device 418, the elevation control device 419, and the Ar blowing amount control device 420. Upon receipt of the control signal, each control device controls the molten steel flow by changing the magnetic field strength, the slab drawing speed, the immersion depth of the immersion nozzle 425, and the Ar blowing amount along the control signal.

[0240] Also, the data analyzer 416, based on the above-mentioned (23) to (32), the mold long sides copper plate temperature, the mold long sides copper plate thickness (d _m), the above distance (d), the molten steel temperature , Using the data such as cooling water temperature
3. Estimate the molten steel flow velocity in 3. Then, the molten steel flow velocity distribution in the width direction of the copper plate 404 on the long side of the mold is captured, and the difference between the maximum value and the minimum value of the captured molten steel flow velocity distribution is preferably 0.25 m / sec or less. 25, the magnetic field strength control device 417, the slab drawing speed control device 418, and the elevating control device so that the difference in molten steel flow velocity at symmetrical positions in the width direction left and right of the copper plate 404 on the long side of the mold is 0.20 m / sec or less. 419, the control signal is transmitted to any one or more of the Ar blowing amount control devices 420. Upon receipt of the control signal, each control device controls the molten steel flow by changing the magnetic field strength, the slab drawing speed, the immersion depth of the immersion nozzle 425, and the Ar blowing amount along the control signal.

In the case of controlling using the magnetic field generator 411, the experience of the present inventors is that it takes 30 seconds for the molten steel flow in the mold 407 to reach a steady state, so an interval of at least 30 seconds is required. It is preferable to change the magnetic field strength separately. It should be noted that among the 15 variables constituting the equations (23) to (32) shown in Table 7, it varies depending on the casting conditions,
Moreover, as variables that cannot be directly measured during casting, solidified shell thickness (d _S ), mold powder layer thickness (d _P ),
There are three variables of the heat transfer coefficient (h _W ) between the mold copper plate and the cooling water. For these three variables, the changes in the numerical values due to the change of the casting conditions were investigated in advance by the actual machine test or the simulated test. The molten steel flow velocity may be calculated based on the numerical value corresponding to the casting condition when measuring the temperature of the copper plate in the mold. The other 12 variables can be determined by the equipment conditions and the physical property values.

By controlling the molten steel flow in the mold in this manner, the molten steel flow in the mold is controlled online and in real time to an appropriate flow pattern, and a slab excellent in cleanliness can be stably manufactured. It becomes possible to do.
In the above description, the temperature measuring element 406 is the copper plate 40 on the long side of the mold.
4 are installed in one row in the width direction, but a plurality of rows can be installed in the casting direction. Also, the above explanation is for the copper plate 4 on the long side of the mold.
Although the temperature measuring element 406 is installed only on one side of the mold 04, it may be installed on both long side copper plates 404 of the mold. Further, the position of the Ar blown into the molten steel outflow hole 432 is determined by the upper nozzle 42.
The fixing plate 429 and the immersion nozzle 42 are not limited to eight.
It may be set to 5.

[Embodiment 1] An embodiment in which molten steel flow control in a mold is carried out by using the slab continuous casting machine shown in FIG. 78 will be described below. The continuous casting machine is a vertical bending mold having a vertical portion of 3 m, and can cast a slab of maximum 2100 mm. Table 8 shows the specifications of the continuous casting machine used.

[0244]

[Table 8]

The long side mold copper plate has a thickness (d _m ) of 40 mm, and an alumel chromel (JIS thermocouple K) is used as a temperature measuring element from the molten steel side surface of the mold copper plate to the thermocouple tip (temperature measuring junction). The distance (d) is 13 mm, the distance between adjacent thermocouples is 66.5 mm, and the distance from the meniscus is 5 mm.
The length was 0 mm, and the thermocouple was embedded over the length of the mold in the width direction of 2100 mm. And thickness 220mm, width 1875
mm slab, slab drawing speed 1.60 m / min, A
Casting was performed by applying a moving magnetic field with a magnetic field generator in a direction that brakes the discharge flow under the conditions of r blowing rate of 10 Nl / min and immersion depth of the immersion nozzle of 260 mm. Table 9 shows the specifications of the magnetic field generator.

[0246]

[Table 9]

Initially, the magnetic flux density of the magnetic field generator was set to 0.03.
It was cast as Tesla, and FIG. 80 was obtained as the temperature distribution of the copper plate temperature on the long side of the mold at that time. In this temperature distribution, the temperature near the copper plate on the short side of the mold was high, and therefore, it was estimated that the molten steel flow velocity near the copper plate on the short side of the mold was fast in the meniscus. In this case, the corresponding molten steel flow condition in the mold was estimated to be Fig. 81. This flow pattern corresponds to pattern A in Japanese Patent Laid-Open No. 10-109145.

Then, when the electric power supplied to the magnetic field generator was increased and the magnetic flux density was set to 0.05 Tesla, the temperature distribution of the copper plate on the long side of the mold became the temperature distribution shown in FIG. In this temperature distribution, the difference between the maximum value and the minimum value was 8 ° C, and the temperature difference at the symmetrical position in the mold width direction was also 10 ° C or less.
Therefore, the molten steel flow velocity in the meniscus was estimated to be almost uniform in the width direction of the mold, and in this case, the corresponding molten steel flow condition in the mold was estimated to be FIG. 83. This flow pattern corresponds to pattern B in Japanese Patent Laid-Open No. 10-109145.

Next, when the power supplied to the magnetic field generator was further increased and the magnetic flux density was set to 0.07 Tesla, the temperature distribution of the copper plate on the long side of the mold became the temperature distribution shown in FIG.
In this temperature distribution, the temperature in the vicinity of the immersion nozzle is high, and therefore the molten steel flow velocity in the meniscus is estimated to be the fastest in the vicinity of the immersion nozzle. In this case, the corresponding molten steel flow condition in the mold was estimated to be FIG. This flow pattern is disclosed in JP-A-1
This corresponds to the pattern C of 0-109145.

As described above, it was found that by controlling the magnetic field intensity of the magnetic field generator, the molten steel flow condition in the mold can be controlled to an appropriate flow pattern. The 81st
In FIG. 83, FIG. 85 and FIG. 85, the white arrows indicate the moving direction of the moving magnetic field.

[Embodiment 2] Using the same continuous casting machine and temperature measuring device as in Embodiment 1, the thickness is 220 mm and the width is 1600.
mm slab, slab drawing speed 1.30 m / min, A
Casting was performed by applying a moving magnetic field with a magnetic field generator in a direction that brakes the discharge flow under the conditions of r blowing rate of 10 Nl / min and immersion depth of the immersion nozzle of 260 mm. Initially, when the magnetic flux density of the magnetic field generator was set to 0.13 Tesla, the temperature distribution of the copper plate temperature on the long side of the mold became the temperature distribution shown in FIG. In this temperature distribution, the temperature on the right side of the center of the slab width direction is higher than that on the left side. Therefore, in the meniscus, it is estimated that the molten steel flow velocity on the right side is faster than the molten steel flow velocity on the left side. That is, there is a drift on the left and right in the mold width direction.
Therefore, when the magnetic flux density of the magnetic field generator was increased to 0.17 Tesla, the temperature distribution shown in FIG. 87 was obtained. In this temperature distribution, the difference between the maximum value and the minimum value was 9 ° C, the temperature difference at the symmetrical positions was 10 ° C or less, and it was estimated that the meniscus flow velocity was almost equal on both sides of the mold width. In this state, the molten steel flow velocity of the meniscus was measured using an immersion rod type molten steel flow velocity meter, and it was confirmed that the molten steel flow pattern in the mold was pattern B.

[Embodiment 3] Using the same continuous casting machine and temperature measuring device as in Embodiment 1, thickness 220 mm, width 1600
A slab having a diameter of 10 mm was cast under the conditions that the amount of Ar blown was 10 Nl / min and the immersion depth of the immersion nozzle was 260 mm. In this example, the magnetic field generator was not used for casting.

Initially, the cast strip drawing speed was set to 1.60 m / mi.
When cast with n, the temperature distribution of the copper plate temperature on the long side of the mold became the temperature distribution shown in FIG. 88. In this temperature distribution, the temperature distribution has maximum values near the copper plate on the shorter side of the mold and near the dipping nozzle. From this temperature distribution, in the meniscus, it was estimated that the molten steel flow velocity near the copper plate on the short side of the mold and around the dipping nozzle was fast. That is, the molten steel flow in the vicinity of the copper plate on the short side of the mold is a flow caused by the upward flow generated after the discharge flow from the immersion nozzle collides with the short side solidification shell and branches up and down. The flow is a flow caused by an upward flow of molten steel that is induced when Ar blown into the immersion nozzle floats near the discharge port of the immersion nozzle. At the position where these molten steel flows meet, that is, at the midpoint between the copper plate on the short side of the mold and the immersion nozzle, it is considered that the flows of the two cancel each other and the molten steel flow velocity becomes smaller, and the temperature distribution actually measured is minimal. There was value.

Therefore, the withdrawal speed of the cast slab is reduced to 1.3.
When it was set to 0 m / min, the temperature distribution shown in FIG. 89 was obtained. In this temperature distribution, the difference between the maximum value and the minimum value is 12
It was estimated that the temperature difference was 10 ° C. or less, and the temperature difference at the symmetrical positions was 10 ° C. or less, and the meniscus flow velocity was almost equal on both sides of the mold width. In this state, the molten steel flow velocity of the meniscus was measured using an immersion rod type molten steel flow velocity meter, and it was confirmed that the molten steel flow pattern in the mold was pattern B. This is because the discharge flow is slowed because the slab drawing speed is reduced,
It is considered that the discharge flow did not reach the solidified shell on the short side of the mold and was dispersed from the discharge port to the solidified shell on the short side.

[Embodiment 4] Using the same continuous casting machine and temperature measuring device as in Embodiment 1, thickness 220 mm, width 1000
mm slab, cast slab drawing speed 1.50 m / min, A
Casting was performed by applying a moving magnetic field with a magnetic field generator in the direction of braking the discharge flow under the condition of r blowing rate of 10 Nl / min. Initially, when the magnetic flux density of the magnetic field generator was 0.03 Tesla and the immersion depth of the immersion nozzle was 180 mm, casting was performed, and the temperature distribution of the copper plate temperature on the long side of the mold was the temperature distribution shown in FIG. 90. In this temperature distribution, the temperature distribution has a maximum value near the immersion nozzle. From this temperature distribution, it was estimated that the molten steel flow velocity around the immersion nozzle was high in the meniscus. That is, it was found that the molten steel flow was mainly composed of the flow caused by the upward flow of the molten steel induced when Ar blown into the immersion nozzle floated near the discharge port of the immersion nozzle.

Therefore, when the immersion depth of the immersion nozzle was increased to 230 mm while maintaining the magnetic flux density at 0.03 Tesla, the temperature distribution shown in FIG. 91 was obtained. In this temperature distribution, the difference between the maximum value and the minimum value was 9 ° C, the temperature difference at the symmetrical positions was 10 ° C or less, and it was estimated that the meniscus flow velocity was almost equal on both sides of the center of the mold width.
In this state, the molten steel flow velocity of the meniscus was measured using an immersion rod type molten steel flow velocity meter, and it was confirmed that the molten steel flow pattern in the mold was pattern B. It is considered that this is because the ascending flow near the immersion nozzle came to rise to a position away from the immersion nozzle because the immersion depth of the immersion nozzle was increased, and the ascending flow velocity near the immersion nozzle was substantially reduced.

[Embodiment 5] Using the same continuous casting machine and temperature measuring device as in Embodiment 1, thickness 220 mm, width 1600
mm slab, slab drawing speed 2.0m / min, A
Under a condition of r blowing amount of 10 Nl / min and immersion depth of the immersion nozzle of 220 mm, a moving magnetic field was applied in a direction in which the discharge flow was braked by the magnetic field generator to perform casting. The magnetic field generator can individually adjust the strength of the applied magnetic field on the left and right in the mold width direction with the immersion nozzle as a boundary. Initially,
When the right and left magnetic flux densities of the magnetic field generator were set to 0.06 tesla, the temperature distribution of the copper plate temperature on the long side of the mold was the temperature distribution shown in FIG. In this temperature distribution, the temperature distribution on the right side is higher than that on the left side with the center in the width direction of the mold as a boundary, therefore,
In the meniscus, it was estimated that the molten steel flow velocity on the right side was faster than the molten steel flow velocity on the left side. That is, there is a drift on the left and right in the mold width direction.

Therefore, when the magnetic flux density of the magnetic field generator was increased to 0.065 Tesla only on the right side of the mold, the temperature distribution shown in FIG. 93 was obtained, and the drift on the left and right in the mold width direction was relaxed. Furthermore, when the magnetic flux density of the magnetic field generator was increased to 0.07 Tesla only on the right side of the mold, the temperature distribution shown in FIG. 94 was obtained. In this temperature distribution, the difference between the maximum value and the minimum value was 12 ° C., the temperature difference at the bilaterally symmetrical position in the mold width direction was also 10 ° C. or less, and it was estimated that the meniscus flow velocity was almost equal on both sides of the mold width.

In this state, the molten steel flow velocity in the meniscus was measured using a dipping rod type molten steel flow velocity meter, and it was confirmed that the molten steel flow pattern in the mold was pattern B. For confirmation,
When the magnetic flux density of the magnetic field generator on the right side of the mold was returned to 0.06 Tesla, which is the same as that on the left side, the temperature distribution shown in FIG. 95 was obtained. In this temperature distribution, it was confirmed that the temperature distribution on the right side in the mold width direction was higher than that on the left side, and the condition returned to the original state where there was a drift on the left and right in the mold width direction.

FIG. 96 shows the transition of the mold copper plate temperature measured by thermocouples installed at positions 665 mm apart on the left side and the right side from the center of the mold width direction. It can be seen that the bias current is controlled by applying left and right independent magnetic fields. In this example, the method of increasing the strength of the magnetic field on the side of strong flow is adopted, but the method of weakening the strength of the magnetic field on the side of weak flow may be adopted. Further, when the moving magnetic field is applied in the direction of accelerating the flow, a method of weakening the magnetic field strength on the strong flow side or a method of increasing the magnetic field strength on the weak flow side can be adopted. .

[Brief description of drawings]

FIG. 1 is a schematic view showing a flow pattern of molten steel in a mold in Best Mode 1.

FIG. 2 is a diagram showing a relationship between a flow pattern of molten steel in a mold and an amount of defective products in the best mode 1.

FIG. 3 is a schematic front sectional view of a continuous casting machine mold unit showing an example of an embodiment of the best mode 1.

FIG. 4 is a schematic side sectional view of a casting mold part showing an example of an embodiment of the best mode 1.

FIG. 5 is a diagram showing temperature transitions at two measurement points in Example 1 of the best mode 1.

FIG. 6 is a diagram showing measurement points according to changes in temperature over time from the temperature measurement result in Example 1 of the best mode 1.

FIG. 7 is a diagram showing changes in the flow pattern detected from temperature analysis results in Example 1 of the best mode 1.

FIG. 8 is a diagram showing a distribution of surface velocity of molten steel in a mold measured by a refractory rod in Example 1 of the best mode 1.

FIG. 9 is a diagram showing temperature transitions at two measurement points after increasing the strength of the magnetic field in Example 1 of the best mode 1.

FIG. 10 is a diagram showing mold long side copper plate temperatures before and after correction in Example 2 of the best mode 1.

FIG. 11 is a diagram showing a molten steel flow velocity measured with a refractory rod in Example 2 of the best mode 1.

FIG. 12 is a diagram showing a measurement result of a molten steel flow velocity profile in the vicinity of a meniscus under a casting condition of level 1 in the best mode 2.

FIG. 13 is a diagram showing measurement results of a molten steel flow velocity profile in the vicinity of a meniscus under a level 2 casting condition in Best Mode 2.

FIG. 14 is a diagram showing a measurement result of a molten steel flow velocity profile in the vicinity of a meniscus under a level 3 casting condition in Best Mode 2.

FIG. 15 is a diagram showing an installation position of a temperature measuring element for accurately capturing the molten steel flow velocity profile in the best mode 2 by the temperature measuring element.

FIG. 16 is a diagram showing a flow velocity distribution directly below a meniscus measured by a water model in Best Mode 2.

FIG. 17 is a diagram showing a calculation result of an autocorrelation coefficient of a molten steel flow velocity measured by a molten steel flow velocity meter of a refractory rod in Best Mode 2.

FIG. 18 is a diagram showing an electrical equivalent circuit of a model which is an output of the temperature measuring element in which the temperature change on the molten steel side of the mold copper plate in the best mode 2 is output.

FIG. 19 is a diagram showing an electrical equivalent circuit of a model serving as an output of the temperature measuring element in which the temperature change on the molten steel side of the mold copper plate in the best mode 2 is output.

FIG. 20 is a diagram showing changes in the mold copper plate temperature at various positions in the mold copper plate when a step signal is applied to the surface of the mold copper plate on the molten steel side in Best Mode 2.

FIG. 21 is a diagram schematically showing a temperature distribution from molten steel to cooling water for a mold copper plate in Best Mode 2.

FIG. 22 is a diagram showing a flow pattern of molten steel in a mold and a mold copper plate temperature distribution in the mold width direction in Best Mode 2.

FIG. 23 is a schematic front cross-sectional view of a continuous casting machine mold part showing an example of an embodiment in Best Mode 2.

FIG. 24 is a schematic side cross-sectional view of a mold part of a continuous casting machine showing an example of an embodiment in Best Mode 2.

FIG. 25 is a schematic side cross-sectional view of a mold part of a continuous casting machine showing a temperature measuring element mounting structure in Best Mode 2.

FIG. 26 is a diagram showing an example of a relationship between a mold copper plate temperature and a molten steel flow rate in Best Mode 2.

FIG. 27 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 1 of Best Mode 2.

FIG. 28 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 1 of Best Mode 2.

FIG. 29 is a diagram showing a distribution of molten steel flow velocity estimated from a mold copper plate temperature in Example 1 of Best Mode 2.

FIG. 30 is a diagram showing a distribution of a molten steel flow velocity estimated from a mold copper plate temperature in Example 1 of Best Mode 2.

FIG. 31 is a diagram showing a molten steel flow velocity distribution in the mold measured in the first heat of continuous casting in Example 2 of Best Mode 2.

FIG. 32 is a diagram showing a mold copper plate temperature distribution measured in the fifth heat of continuous casting in Example 2 of the best mode 2.

FIG. 33 is a diagram showing a molten steel flow velocity distribution in the mold measured in the fifth heat of continuous casting in Example 2 of Best Mode 2.

FIG. 34 is a diagram showing a molten steel flow velocity distribution in the mold measured in the first heat of continuous casting in Example 3 of Best Mode 2.

FIG. 35 is a diagram showing a mold copper plate temperature distribution measured in a third heat of continuous casting in Example 3 of the best mode 2.

FIG. 36 is a diagram showing a molten steel flow velocity distribution in the mold measured in the third heat of continuous casting in Example 3 of Best Mode 2.

FIG. 37 is a diagram schematically showing a comparison between the flow state of molten steel in a mold and the profile of the mold copper plate temperature in Best Mode 3.

38 is a diagram schematically showing the widthwise distribution of mold copper plate temperatures and the maximum, minimum, and average mold copper plate temperatures when the molten steel flow condition is pattern 1 in the best mode 3. FIG.

FIG. 39 is a diagram schematically showing the widthwise distribution of the mold copper plate temperature and the maximum and minimum values of the mold copper plate temperature when the molten steel flow condition is the pattern 2 in the best mode 3.

FIG. 40 is a schematic front cross-sectional view of a mold part of a continuous casting machine in Best Mode 3.

FIG. 41 is a view showing a result of investigation in Example 1 of the best mode 3, showing a relationship between the maximum value (T _max ) of the temperature of the copper plate in the mold and the surface defect of the cold rolled coil.

FIG. 42 is a view showing a result of investigation in Example 2 of the best mode 3, showing a relationship between the minimum value (T _min ) of the temperature of the mold copper plate and the blow defect and the slag defect on the surface of the slab.

FIG. 43 is a diagram showing the results of investigation in Example 3 of the best mode 3, showing the relationship between the maximum height difference, the maximum left-right temperature difference, and the surface defect of the cold-rolled coil.

FIG. 44 is a result of investigation in Example 4 of the best mode 3, and is a diagram showing a relationship between an average copper plate temperature (T _ave ) and a maximum difference in height and a blow flaw and a slag defect on the surface of the cast slab.

FIG. 45 is a diagram showing measured values of mold copper plate temperatures in Example 5 of Best Mode 3;

[Fig. 46] Fig. 46 is a result of an examination in Example 5 of the best mode 3, and is a diagram showing changes in the maximum value of the temperature fluctuation amount, corresponding to the cold rolling coil.

[Fig. 47] Fig. 47 is a result of an examination in Example 6 of the best mode 3, and is a diagram showing a relationship between a cast strip drawing speed and an average copper sheet temperature (T _ave ) for each surface defect occurrence rate of a cold rolled coil.

FIG. 48 is a diagram showing a measurement result of a molten steel flow velocity profile under level 1 casting conditions of Best Mode 4.

FIG. 49 is a diagram showing measurement results of molten steel flow velocity profile under level 2 casting conditions of Best Mode 4.

FIG. 50 is a diagram showing a measurement result of a molten steel flow velocity profile under a casting condition of level 3 of the best mode 4.

FIG. 51 is a diagram showing a change over time in the temperature of the copper plate on the long side of the mold when the magnetic flux density of the magnetic field generator is changed in Best Mode 4.

FIG. 52 is a diagram collectively showing a transition period of a temperature change of a long side copper plate of a mold in Best Mode 4.

FIG. 53 is a schematic front cross-sectional view of a mold part of a continuous casting machine in Best Mode 4.

FIG. 54 is a diagram showing a temperature distribution in the mold width direction based on the collected raw data of the long-side copper plate temperature of the mold in Example 1 of Best Mode 4.

FIG. 55 is a diagram showing a result of calculating a change in the attenuation amount R due to a change in the averaged number M in the best mode 4.

56 is a temperature distribution diagram obtained by spatially moving average of the temperature distribution shown in FIG. 54. FIG.

FIG. 57 is a diagram showing a temperature distribution in the mold width direction based on the collected raw data of the long-side copper plate temperature of the mold in Example 2 of Best Mode 4.

FIG. 58 shows the temperature distribution shown in FIG.
It is a distribution diagram of the temperature which carried out the space moving average as.

FIG. 59 shows the temperature distribution shown in FIG.
It is a distribution diagram of the temperature which carried out the space moving average as.

FIG. 60 shows the temperature distribution shown in FIG.
It is a distribution diagram of the temperature which carried out the space moving average as.

FIG. 61 is a temperature distribution diagram of spatial moving average in Example 3 of the best mode 4 when the thermocouple embedding interval is 100 mm and the number of averaged temperature distributions is 3.

FIG. 62 is a temperature distribution diagram of spatial moving average in Example 3 of the best mode 4 when the thermocouple embedding interval is 150 mm and the number of averaged temperature distributions is 3.

FIG. 63 is a temperature distribution chart of spatial moving average using the data obtained by folding back and expanding the data at the end points in Example 4 of the best mode 4.

FIG. 64 is a diagram showing a change over time in the temperature of the copper plate on the long side of the mold when the data collection interval is set to 1 second in Example 5 of Best Mode 4.

FIG. 65 is a diagram showing a time-dependent change in copper plate temperature on the long side of the mold when the data collection interval is set to 5 seconds in Example 5 of Best Mode 4.

FIG. 66 is a diagram showing a change over time in the temperature of the copper plate on the long side of the mold when the data collection interval is 10 seconds in Example 5 of Best Mode 4.

FIG. 67 is a diagram showing a time-dependent change in the temperature of the copper plate on the long side of the mold when the data collection interval was set to 60 seconds in Example 5 of Best Mode 4.

[Fig. 68] Fig. 68 is a diagram showing a time-dependent change in copper plate temperature on the long side of the mold when the data collection interval is 240 seconds in Example 5 of Best Mode 4.

69. In Example 6 of the best mode 4, the standard value (σ) of the average value (Do) in the mold width direction and the solidified shell thickness.
It is a figure which shows the relationship with.

70 is a diagram showing an example of molten steel flow velocity distribution at a meniscus in the case where the flow pattern of molten steel in a mold is pattern B in the best mode 5. FIG.

71 is a diagram showing a temperature distribution example of copper plate temperature on the long side of the mold in the case where the flow pattern of the molten steel in the mold is pattern B in the best mode 5. FIG.

72 is a diagram schematically showing a temperature distribution from molten steel to cooling water for a mold copper plate in Best Mode 5. FIG.

FIG. 73 is a diagram showing an example of a relationship between a mold copper plate temperature and a molten steel flow rate in Best Mode 5.

FIG. 74 is a diagram showing an example of measurement results of temperature of copper plate on long side of mold in best mode 5.

FIG. 75 is a diagram showing another example of the measurement results of the copper plate temperature on the long side of the mold in Best Mode 5.

76 is a diagram in which the temperature of the copper plate on the long side of the mold shown in FIG. 74 is converted into a molten steel flow rate.

77 is a diagram in which the temperature of the copper plate on the long side of the mold shown in FIG. 75 is converted into a molten steel flow rate.

[Fig. 78] Fig. 78 is a schematic front sectional view of a continuous casting machine showing an example of an embodiment of Best Mode 5.

79 is a schematic side sectional view of a continuous casting machine showing an example of an embodiment of Best Mode 5. FIG.

FIG. 80 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 1 of Best Mode 5.

81 is a diagram showing a molten steel flow condition estimated from the temperature distribution of FIG. 80. FIG.

82 is a diagram showing an example of measurement results of mold copper plate temperature in Example 1 of Best Mode 5. FIG.

83 is a diagram showing a molten steel flow condition estimated from the temperature distribution of FIG. 82. FIG.

FIG. 84 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 1 of Best Mode 5.

85 is a diagram showing a molten steel flow condition estimated from the temperature distribution of FIG. 84. FIG.

FIG. 86 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 2 of Best Mode 5.

FIG. 87 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 2 of Best Mode 5.

FIG. 88 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 3 of Best Mode 5;

89 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 3 of Best Mode 5. FIG.

90 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 4 of Best Mode 5. FIG.

FIG. 91 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 4 of Best Mode 5.

92 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 5 of Best Mode 5. FIG.

FIG. 93 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 5 of Best Mode 5.

FIG. 94 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 5 of Best Mode 5.

FIG. 95 is a diagram showing an example of measurement results of mold copper plate temperatures in Example 5 of Best Mode 5.

FIG. 96 is a diagram showing an example of changes over time in the temperature of the copper plate on the long side of the mold when the magnetic flux density of the magnetic field generator was changed in Example 5 of Best Mode 5.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Jun Kubota             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Noriko Kubo             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Junichi Kadota             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Yuichi Yamaoka             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Yoshimitsu Isobe             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. F-term (reference) 4E004 AA09 HA01 MA05 MB04

Claims (30)

[Claims] 1. A method for estimating a molten steel flow pattern in continuous casting comprises the following steps: continuously casting molten steel discharged from a dipping nozzle into a mold; A step of measuring a plurality of points by a temperature measuring device; and a step of estimating a flow pattern of molten steel in the mold from the distribution of the copper plate temperature at each measurement point. 2. The molten steel flow pattern estimation method according to claim 1, further comprising the step of applying a magnetic field to the molten steel discharged into the mold so that the detected flow pattern becomes a predetermined pattern. 3. The molten steel flow pattern estimation method according to claim 1, further comprising the following steps: Mold copper plate temperature measured by a mold copper plate temperature measuring device, mold copper plate thickness, and mold copper plate molten steel. The distance from the side surface to the tip of the temperature measuring element, the cooling water temperature for the mold copper plate, the solidification shell thickness,
A process of determining the heat flux from the molten steel in the mold to the cooling water for the copper plate for the mold using the thickness of the mold powder layer and the temperature of the molten steel in the mold; convective heat transfer between the molten steel and the solidified shell corresponding to this heat flux The step of obtaining the coefficient; the step of obtaining the flow velocity of the molten steel along the solidified shell from the convection heat transfer coefficient. 4. A temperature measuring device for temperature of a mold copper plate comprises a plurality of temperature measuring elements embedded in the back surface of the mold copper plate for continuous casting,
The temperature measuring element, the distance from the molten steel side surface of the mold copper plate to the tip of the temperature measuring element is 16 mm or less in the range of 10 to 135 mm away from the molten steel surface position in the mold in the slab drawing direction,
Further, the molds are installed over a range corresponding to the entire width of the slab, with an installation interval in the width direction of the mold being 200 mm or less.
Method for estimating flow pattern of molten steel described. 5. The flow of molten steel according to claim 1, wherein the step of estimating the flow pattern comprises estimating the flow pattern of the molten steel in the mold based on the number of peaks and the positions of the peaks of the mold copper plate temperature in the width direction of the mold. Pattern estimation method. 6. The step of estimating the flow pattern comprises comparing the maximum value of the mold copper plate temperature with the position of the maximum value on the left and right of the mold width direction with reference to the center position of the mold width direction based on the measured temperature. The method for estimating a molten steel flow pattern according to claim 1, wherein the drift of the molten steel in the mold is estimated by. 7. A mold copper plate temperature measuring device comprises: a plurality of temperature measuring elements embedded in the back surface of the mold copper plate for continuous casting; the temperature measuring elements extending from the molten steel surface position in the mold toward the slab drawing direction. Installed over a range corresponding to the entire width of the slab, with the distance from the molten steel side surface of the mold copper plate to the tip of the temperature measuring element being 16 mm or less, and the installation interval in the mold width direction being 200 mm or less within a range of 10 to 135 mm apart. Has been done. 8. The temperature measuring element is installed so as to penetrate through a pipe sealed from cooling water in a water box, and a seal packing is provided around the temperature measuring element. Item 7. A temperature measuring device according to item 7. 9. The method for determining the surface defects of a continuously cast slab comprises the following: a plurality of temperature measuring elements in the width direction of the back surface of the mold copper plate in the range 10 to 135 mm away from the meniscus position in the mold in the slab drawing direction. Is measured; the widthwise distribution of the temperature of the copper plate in the mold is measured; and the surface defect of the slab is determined based on the temperature distribution in the widthwise direction of the mold. 10. The surface defect determination method according to claim 9, wherein the determination of the surface defect comprises determining the surface defect of the slab based on the maximum value of the temperature distribution in the mold width direction. 11. The surface defect determination method according to claim 9, wherein the determination of the surface defect comprises determining the surface defect of the slab based on the minimum value of the temperature distribution in the mold width direction. 12. The surface defect determination method according to claim 9, wherein the surface defect determination comprises determining the surface defect of the slab based on the average value of the temperature distribution in the mold width direction. 13. A surface defect of a slab is judged based on a difference between an average value of temperature distribution in the mold width direction and a typical average value of temperature distribution in the mold width direction at the slab drawing speed. The method for determining a surface defect according to claim 9, comprising: 14. The determination of the surface defect is performed by determining the value obtained by subtracting the minimum value from the maximum value of the temperature distribution on the left side in the mold width and the temperature distribution on the right side in the mold width around the immersion nozzle arranged in the center of the mold. The surface defect determination method according to claim 9, which comprises determining the surface defect of the slab based on the larger value of the values obtained by subtracting the minimum value from the maximum value. 15. The absolute value of the difference between the maximum value of the temperature distribution on the left side in the mold width direction and the maximum value of the temperature distribution on the right side in the mold width direction centering on the immersion nozzle arranged in the center of the mold for determining the surface defect. The surface defect determination method according to claim 9, which comprises determining the surface defect of the slab based on the above. 16. The surface defect of the slab is determined based on the maximum value of the temperature fluctuation amount per unit time among the temperature measurement values of the temperature measuring elements. Surface defect determination method. 17. A method for detecting molten steel flow in continuous casting comprises the following: a plurality of temperature measuring elements are arranged on a back surface of a casting copper plate for continuous casting in a direction orthogonal to a slab drawing direction; When the spatial frequency f of the molten steel flow is defined as f = 1 / L by using the fluctuation wavelength L (mm) of the molten steel flow, the cutoff spatial frequency is The range is larger than 2 / [mold width W] and smaller than 0.01, and is low-pass filtered; the molten steel flow condition in the mold is estimated based on the temperature distribution of the low-pass filtered mold copper plate temperature. 18. The low-pass filter processing is a spatial moving average, and when the averaging number is 3, the distance between adjacent temperature measuring elements is wider than 44.3 / 3 mm, and 0.443 ×
18. The molten steel flow detection method according to claim 17, wherein the mold width is adjusted to a range narrower than 6 mm. 19. The molten steel flow detection method according to claim 17, which comprises performing a low-pass filtering process using a data series obtained by folding back and expanding the measurement data at the end points of the mold width on both sides. 20. A method for detecting molten steel flow in continuous casting comprises the following: A space between adjacent temperature measuring elements is set to 4 in the direction orthogonal to the drawing direction of the slab on the back surface of the continuous casting mold copper plate.
A plurality of temperature measuring elements are arranged as 4.3 / 3 mm to 0.443 x [mold width W] / 6 mm; the temperature of the mold copper plate is measured by these temperature measuring elements; Moving average is performed; the molten steel flow state in the mold is estimated based on the temperature distribution of the mold copper plate temperature subjected to this spatial moving average. 21. A method for evaluating non-uniformity of heat removal in a mold in continuous casting comprises the following: disposing a plurality of temperature measuring elements on a back surface of a copper plate for continuous casting, in a direction orthogonal to a slab drawing direction; The mold copper plate temperature is measured by these plural temperature measuring elements; each measured mold copper plate temperature is low-pass filtered; based on the difference between the measured mold copper plate temperature and the low-pass filtered mold copper plate temperature Evaluate heat non-uniformity. 22. A method for detecting molten steel flow in continuous casting comprises: arranging a plurality of temperature measuring elements on a rear surface of a continuous casting mold copper plate in a direction orthogonal to a slab drawing direction; The mold copper plate temperature is measured; the measured mold copper plate temperatures are sampled at intervals of 60 seconds or less; the molten steel flow condition in the mold is estimated based on the mold copper plate temperatures collected at these intervals. 23. The molten steel flow control method in continuous casting comprises the following: a plurality of temperature measuring elements are arranged in the width direction of the back surface of the copper plate on the long side of the mold for continuous casting to obtain a temperature distribution in the width direction of the copper plate on the long side of the mold. Measured; the magnetic field strength of the magnetic field generator attached to the mold, the slab drawing speed, the immersion depth of the immersion nozzle, the immersion so that the difference between the maximum value and the minimum value of the measured temperature distribution is 12 ° C or less. Any one or two or more of the amounts of Ar blown into the nozzle are adjusted. 24. The molten steel flow control method according to claim 23, wherein the magnetic field intensity of the magnetic field generator attached to the mold is adjusted independently on the left and right sides of the mold in the width direction of the mold. 25. Any one or two or more of the magnetic field strength of a magnetic field generator attached to the mold, the slab drawing speed, the immersion depth of the immersion nozzle, and the amount of Ar blown into the immersion nozzle are measured. The temperature difference is adjusted so that the difference between the maximum value and the minimum value of the temperature distribution is 12 ° C. or less, and the temperature difference is 10 ° C. or less at the symmetrical positions on the long side of the mold in the width direction of the copper plate with the immersion nozzle as the center. The molten steel flow control method according to claim 23. 26. The molten steel flow control method according to claim 25, wherein the magnetic field strength of the magnetic field generator attached to the mold is adjusted independently on the left and right in the mold width direction with the immersion nozzle as a boundary. 27. The molten steel flow control method in continuous casting comprises: a plurality of temperature measuring elements arranged in the width direction of the back surface of the copper plate on the long side of the mold for continuous casting, and the temperature at each position in the width direction of the copper plate on the long side of the mold. The flow velocity of molten steel at each measurement point is calculated based on the measured temperature value to obtain the molten steel flow velocity distribution in the copper plate width direction of the long side of the mold; the difference between the maximum value and the minimum value of the obtained molten steel flow velocity distribution is 0. Any one or two of the magnetic field strength of the magnetic field generator attached to the mold, the slab drawing speed, the immersion depth of the immersion nozzle, and the amount of Ar blown into the immersion nozzle so as to be 0.25 m / sec or less. Adjust one or more. 28. The molten steel flow control method according to claim 27, wherein the magnetic field strength of the magnetic field generator attached to the mold is adjusted independently on the left and right in the mold width direction with the immersion nozzle as a boundary. 29. Any one or two or more of the magnetic field strength of a magnetic field generator attached to the mold, the slab drawing speed, the immersion depth of the immersion nozzle, and the amount of Ar blown into the immersion nozzle is determined. The difference between the maximum value and the minimum value of the molten steel flow velocity distribution is 0.25 m / sec or less, and the difference in the molten steel flow velocity is 0.20 m / sec at symmetrical positions on the long side of the mold and the width direction of the copper plate with the immersion nozzle as the center. The molten steel flow control method according to claim 27, which is adjusted as follows. 30. The molten steel flow control method according to claim 29, wherein the magnetic field strength of the magnetic field generator attached to the mold is adjusted independently on the left and right in the mold width direction with the immersion nozzle as a boundary.