JP2016175114A - Molten metal surface profile measuring method, device and program in continuous casting mold, and control method of continuous casting - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a measuring accuracy of a molten metal surface profile in a casting mold to permit stable operation by grasping an influence of heat transfer on a molten metal surface position to detect a molten metal level and, thereby, improving a detection accuracy of the molten metal surface level.SOLUTION: An input part 101 inputs measurement values of a plurality of thermocouples 6 which are arranged and embedded in a casting direction in a plurality of positions in a width direction of a casting mold length side of a continuous casting mold 1 and/or in a width direction of a casting mold width side. A calculation part 102 analyses a heat transfer inverse problem by using the inputted measurement values of the thermocouples 6 and calculates a vector component value in the casting direction of a thermal flux on an operating surface on each of the plurality of positions. A molten metal surface profile measuring part 103 judges such a position that the vector component value in a normal direction of a molten metal surface which becomes reverse to the casting direction of the thermal flux on the operating surface calculated on each of the plurality of positions gets to maximum as a molten metal surface level to measure a molten metal surface profile. A control part 104 decreases a casting speed when a difference between a maximum value and a minimum value on the measured molten metal surface profile gets to a predetermined value or more.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a molten metal surface profile measuring method, apparatus, and program in a continuous casting mold (mold), and a continuous casting control method.

In continuous casting operations, it is extremely important to improve the detection accuracy of the molten metal surface level in the mold from the viewpoints of stable casting (preventing casting troubles such as breakout) and slab quality.
In recent years, in continuous casting operations, an electromagnetic stirrer (hereinafter also referred to as EMS) has become widespread from the viewpoint of improving surface quality. When electromagnetic stirring is performed by EMS, the hot water surface level is a short side collision flow formed by the left and right discharge flow of a conventional immersion nozzle, and the hot water surface rise of the short side portion (the hot water surface is relatively low in the center of the width). The hot water surface profile is different from the distribution of. Specifically, since the swirling flow formed by electromagnetic stirring is subjected to pressure loss at the narrow part of the immersion nozzle and the long side of the mold, the surface of the molten metal may be lowered due to the static pressure drop. In this way, the flow in the mold that is electromagnetically agitated by EMS is different from only the discharge flow from the conventional immersion nozzle, and generally forms a complex flow, and the flow due to the discharge flow is generated in this flow. Overlapping and forming a more complex flow shape of the hot water surface.
On the other hand, the molten powder tends to gather at a low part on the surface of the molten steel due to a difference in specific gravity with the molten steel. Therefore, when the molten metal surface level difference becomes large, in a portion where the molten powder thickness is thin, lubrication failure due to insufficient powder flow tends to occur, and the risk of occurrence of breakout or the like increases.

In Patent Document 1, a plurality of temperature measuring elements are embedded at equal intervals along the height direction of the mold wall, and the time change rate value of the temperature at each element point is calculated for each arbitrary period. The element (n) indicating the maximum value of the rate is detected, and the position indicating the maximum value of the quadratic curve connecting the element (n) and the time change rate values of the elements (n−1) and (n + 1) before and after the element (n) And a technique for setting the position to the surface level is disclosed.
In Patent Document 2, the mold temperature is measured by temperature measuring means embedded in a plurality of locations of the mold at intervals in the casting direction, and the heat flux on the inner surface of the mold at each measurement point is calculated based on the measured mold temperature. A technique for estimating each using the inverse heat transfer problem method is disclosed.
Further, in Patent Document 3, the level of the molten steel in the mold is continuously measured by a pair of sensors arranged on the short side of the immersion nozzle on the left and right sides and reciprocating in the mold longitudinal direction. A technique is disclosed in which the casting speed is changed when the difference in the obtained molten metal surface fluctuation exceeds a predetermined value.
In Patent Document 4, a plurality of thermocouples are arranged in the width direction of the mold copper plate to measure the temperature of the mold copper plate. A technique for estimating the above is disclosed.

JP-A-53-26230 JP 2001-239353 A JP-A-2-137655 JP-A-11-90600

  However, the existing method represented by Patent Document 1 is based on an empirical rule that the position where the temperature in the casting direction of the mold is maximum is in the vicinity of the molten metal surface and has a certain correlation with the molten metal surface position. Thus, when based on an empirical rule, there exists a possibility that the detection accuracy of a hot-water surface level may become low. Specifically, the temperature change rate of the thermocouple embedded in the mold depends on the molten steel temperature and the molten steel surface change rate. The higher the molten steel temperature, the greater the temperature change rate. There is a problem that the detection delay of the hot water surface position becomes large due to the time delay of the temperature rise.

  Patent Document 2 is a method for estimating the heat flux using the inverse heat transfer problem, but there is no description about the heat flux, the surface level, and the surface profile measurement.

  In Patent Document 3, since the molten metal surface profile obtained by reciprocating a pair of sensors in the mold longitudinal direction is obtained, only the molten metal surface profile separated from the mold long side and the mold short side can be measured. This is because in order to avoid sensor breakage due to changes in the molten metal surface position, it is necessary to maintain a certain distance between the sensor and the molten metal surface, and generally the measurement area tends to expand. As a result, if the sensor is too close to the mold wall surface, the mold wall surface enters the measurement area and measurement errors are likely to occur. As a result, it is possible to grasp only the offshore surface level change that is duller than the surface level change in the vicinity of the mold wall surface, and it is possible to measure the local rise and decrease in the surface level near the mold wall surface due to the flow in the mold. Can not.

  In Japanese Patent Laid-Open No. 2004-260260, the amount of fluctuation of the molten metal surface can be detected, but the molten metal surface level cannot be detected, and the above-described difference in molten metal surface level cannot be grasped, so that phenomena such as poor lubrication due to insufficient powder flow cannot be grasped.

  The present invention has been made in view of the above points, and by detecting the level of the molten metal level by detecting the influence of heat transfer at the level of the molten metal level, the accuracy of detection of the molten metal level is improved, and the molten metal level in the mold The purpose is to improve the measurement accuracy of the profile and realize stable operation.

In order to solve the above problems, the present invention is as follows.
[1] A method for measuring a molten metal surface profile in a continuous casting mold,
An acquisition step of acquiring measurement values of a plurality of temperature detection means arranged and embedded in the casting direction at a plurality of positions in the width direction of the mold long side and / or the width direction of the mold short side of the continuous casting mold;
A calculation step for solving a heat transfer inverse problem using the measurement value of the temperature detection means acquired in the acquisition step and calculating a component value in the casting direction of the heat flux on the working surface at the plurality of positions;
Based on the component value in the casting direction of the heat flux at the working surface at the plurality of positions calculated in the calculation step, the molten metal surface profile is measured by detecting the surface level at the plurality of positions. And a measuring step. A method for measuring a molten metal surface profile in a continuous casting mold.
[2] In the molten metal surface profile measuring step, the position where the component value in the normal direction of the molten metal surface that is opposite to the casting direction of the heat flux on the working surface at the plurality of positions calculated in the calculating step is maximized. Is determined as a molten metal surface level, [1] The method of measuring a molten metal surface profile in a continuous casting mold according to [1].
[3] [1] or [2], wherein a plurality of temperature detection means are arranged and embedded in the casting direction on the pair of mold short sides and the pair of mold long sides of the continuous casting mold. Of hot water surface profile in continuous casting mold.
[4] When a difference between the maximum value and the minimum value in the molten metal profile obtained by the molten metal profile measuring method in the continuous casting mold according to any one of [1] to [3] exceeds a predetermined value. A control method for continuous casting, characterized in that the casting speed is reduced.
[5] The continuous casting control method according to [4], wherein when the difference between the maximum value and the minimum value in the molten metal surface profile exceeds 15 mm, the casting speed is reduced by 10% or more.
[6] When the difference between the maximum value and the minimum value in the molten metal profile obtained by the molten metal profile measuring method in the continuous casting mold according to any one of [1] to [3] exceeds a predetermined value. The method for controlling continuous casting, wherein the electromagnetic stirring thrust of the electromagnetic stirring device is reduced.
[7] The continuous casting control method according to [6], wherein when the difference between the maximum value and the minimum value in the molten metal surface profile exceeds 15 mm, the electromagnetic stirring thrust is reduced by 20% or more.
[8] A molten metal profile measuring device in a continuous casting mold,
Input means for inputting measured values of a plurality of temperature detection means arranged and embedded in the casting direction at a plurality of positions in the width direction of the mold long side and / or the width direction of the mold short side of the continuous casting mold,
Solving the inverse heat transfer problem using the measured value of the temperature detecting means input by the input means, calculating means for calculating the component value in the casting direction of the heat flux at the working surface at the plurality of positions;
Based on the component value in the casting direction of the heat flux at the operating surface at the plurality of positions calculated by the calculating means, the molten metal level profile is detected by detecting the level of the molten metal level at the plurality of positions. An apparatus for measuring a molten metal surface profile in a continuous casting mold, comprising a measuring means.
[9] A program for measuring a molten metal surface profile in a continuous casting mold,
A process of inputting measured values of a plurality of temperature detecting means arranged and embedded in the casting direction at a plurality of positions in the width direction of the mold long side and / or the width direction of the mold short side of the continuous casting mold,
Processing to solve the inverse heat transfer problem using the input measurement value of the temperature detection means, and calculate the component value in the casting direction of the heat flux at the working surface at the plurality of positions;
Based on the calculated component value in the casting direction of the heat flux on the working surface at the plurality of positions calculated, the computer detects the surface level at the plurality of positions and measures the surface profile. Program to let you.

  According to the present invention, the detection accuracy of the molten metal surface level is improved by detecting the molten metal surface level by detecting the influence of the heat transfer at the molten metal surface position, the measurement accuracy of the molten metal surface profile in the mold is improved, and stable operation is achieved. Can be realized.

It is a figure which shows typically the outline | summary of the continuous casting mold in 1st Embodiment. It is a figure for demonstrating the influence which electromagnetic stirring has on a hot-water surface profile. It is a figure which shows the function structure of the control apparatus of the continuous casting which concerns on 1st Embodiment. It is a figure which shows the coordinate system of a heat transfer inverse problem. It is a figure for demonstrating the outline | summary of the detection of a hot-water surface level. It is a figure which shows the example of an apparatus structure for measuring a hot_water | molten_metal surface level. It is a characteristic view which shows the hot-water surface level detected with the method of this invention, the hot-water surface level detected with the existing method, and the measured hot-water surface level. It is a flowchart which shows the control processing which a control part performs in 1st Embodiment. It is a flowchart which shows the control processing which a control part performs when the casting speed is reduced in 1st Embodiment. It is a flowchart which shows the control processing which a control part performs in 2nd Embodiment. It is a flowchart which shows the control processing which a control part performs when electromagnetic stirring thrust is reduced in 2nd Embodiment.

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.
[First Embodiment]
FIG. 1 schematically shows an outline of a continuous casting mold (hereinafter simply referred to as a mold) 1. The mold 1 includes a pair of mold short sides 2a and 2b facing each other and a pair of mold long sides 3a and 3b facing each other. The inner surface of the mold 1 is called the working surface, and the outer surface is called the water-cooled surface. That is, of the surfaces of the mold 1, the surface that contacts the molten metal is the working surface (however, when lubricating powder is used, it contacts the molten metal through the lubricating powder).
An immersion nozzle 4 is disposed at the center of the mold 1, and molten steel is discharged from the left and right discharge holes 4 a, 4 b of the immersion nozzle 4 toward the left and right mold short sides 2 a, 2 b. Reference numeral 5 indicates a hot water surface. Although FIG. 1 shows an example having a pair of left and right discharge holes 4a and 4b, a plurality of right and left discharge holes may be provided.

A plurality of thermocouples 6 are arranged and embedded in the casting direction at a plurality of positions in the width direction of the mold short side and / or the width direction of the mold short side of the mold 1. In the present embodiment, a plurality of thermocouples 6 are arranged and embedded in the casting direction at five locations on each of the pair of mold long sides 3a and 3b. In addition, a plurality of thermocouples 6 are arranged and embedded in the casting direction at each one of the pair of mold short sides 2a and 2b.
For the purpose of measuring the molten metal surface profile (the shape of the molten metal surface), it is preferable that the rows of the thermocouples 6 be arranged at equal intervals or at intervals close thereto without being biased in the circumferential direction of the mold 1.

  An electromagnetic stirrer (EMS) 7 is disposed around the mold 1. The electromagnetic stirrer 7 rotates the magnetic field in the mold 1 to create a flow in the molten steel so that inclusions remain on the surface of the solidified shell and do not solidify. The arrow 8 in FIG. 2 indicates the molten steel flow vector in the electromagnetic stirring application region. As shown in FIG. 2, the swirling flow formed by electromagnetic stirring is subject to pressure loss at the narrow part of the immersion nozzle and the long side of the mold, so that the molten metal surface is lowered due to the static pressure drop, and the main flow is below the molten metal surface. It becomes a flow to get into. The flow that collides with the mold short side 2b is divided into upper and lower parts, and the raised flow forms a flow that reverses in the direction of the immersion nozzle 4 on the molten metal surface and pushes up the molten metal surface near the short side 2b (in FIG. Only the flow separated upward from the flow colliding with the side 2b is shown).

FIG. 3 shows a functional configuration of the continuous casting control apparatus 100 according to the first embodiment. In the present embodiment, the control device 100 also functions as a molten metal profile measuring device in a continuous casting mold to which the present invention is applied.
Reference numeral 101 denotes an input unit for inputting measured values of a plurality of thermocouples 6 arranged and embedded in a casting direction at a plurality of positions of the mold 1. In this embodiment, as shown in FIG. 1, the measured values of the thermocouples 6 in 5 rows each of the mold long sides 3a and 3b and the measured values of the thermocouple 6 in 1 row each of the mold short sides 2a and 2b are input. .
Reference numeral 102 denotes a calculation unit, which will be described in detail later, but solves the inverse heat transfer problem using the measured value of the thermocouple 6 input at the input unit 101, and at each of a plurality of positions, in the casting direction of the heat flux on the working surface. The vector component value, in other words, the vector component value in the direction perpendicular to the surface of the heat flux on the operating surface is calculated.

103 is a molten metal surface profile measuring unit, and at each of a plurality of positions, the position where the vector component value in the normal direction of the molten metal surface opposite to the casting direction of the heat flux on the working surface calculated by the calculating unit 102 is maximized. Is determined as the hot water level, and the hot water surface profile is measured. That is, the hot water level obtained at each of a plurality of positions at the same timing is used as the hot water surface profile at the timing. In this case, the hot water surface level may be obtained by interpolating the hot water surface level obtained in each row between a certain thermocouple 6 row and the adjacent thermocouple 6 row.
Reference numeral 104 denotes a control unit, which will be described in detail later, but the difference between the maximum value and the minimum value (hereinafter also referred to as a difference in molten metal surface height) in the molten metal surface profile measured by the molten metal surface profile measuring unit 103 is a predetermined value or more. The casting speed is reduced.
The input unit 101, the calculation unit 102, the molten metal profile measuring unit 103, and the control unit 104 are, for example, at regular intervals, input of measurement values of the thermocouple 6, calculation of vector component values, measurement of molten metal profile, and casting speed. Execute the control.

(About detection of hot water level)
In the continuous casting operation, powder is added into the mold 1 to keep the molten steel warm and prevent oxidation, absorb inclusions in the molten steel, ensure the lubricity of the solidified shell, and adjust the heat removal. As a result, a solidified shell is uniformly formed at the meniscus in the mold to prevent surface cracks, and seizure between the mold and the solidified shell is prevented.
Since powder is supplied onto the molten metal surface in the mold 1 in this way, in the present invention, “the heat flux value perpendicular to the molten metal surface and upward due to the effect of heat removal by the powder is compared with other parts of the mold. The hot water level is detected based on the inference that “It is the largest.”

Hereinafter, the inverse heat transfer problem for estimating the heat flux vector of the working surface based on the measurement data of the plurality of thermocouples 6 embedded in the mold 1 will be described.
Based on the time series data set of a plurality of thermocouples 6 embedded in the mold 1, the time of the two-dimensional cross-sectional temperature distribution in the casting direction and the heat removal direction of the mold 1 is used as the extrapolated temperature function u ^* for temperature estimation. Create mathematical formulas to predict changes. Based on this formula, the heat flux vector (size and direction) on the working surface is obtained and used as a basic physical quantity for determining the molten metal surface level.

FIG. 4 shows a coordinate system for the inverse heat transfer problem. The space x-axis is the heat removal direction where the working surface is x = 0, and the space y-axis is the casting direction where the upper end of the mold 1 is y = 0. .
The plot of FIG. 4 shows the definition points of the information amount used for the calculation on the two-dimensional sectional view of the space x-time t at a certain y. The measurement data of the thermocouple 6 is used as the information amount of the thermocouple position on the x axis. On the other hand, since there is no thermocouple at the position of the water-cooled surface, the heat-cooled heat transfer coefficient and the heat flux value determined as the water temperature are used as the information amount, and together with the above-mentioned thermocouple position, it is defined as the temperature measurement data collection point area To do. This region is expanded to the thermocouple position in the y-axis direction, and is set as a region of the three-dimensional temperature measurement data collection point in space x-space y-time t.
The heat flux vector on the working surface is estimated using the interpolated temperature function u ^* (x, y, t) created based on the information amount of the region of the three-dimensional temperature measurement data collection point described above.

The mathematical procedure for constructing the extrapolated temperature function u ^* (x, y, t) is described below.
Consider the unsteady heat conduction equation of equation (1). Here, a is a physical quantity of the square root of the thermal diffusion coefficient of the mold 1. The position coordinates x and y are normalized by [0, 1].

The boundary condition of the cooling surface is expressed by equation (2). Here, g (t) = u _w γ, which is defined as the product of the water temperature u _w and the heat transfer coefficient γ. β is the thermal conductivity of the mold 1.

The thermocouple temperature information of the mold 1 is described by equation (3). x ^* and y ^* represent thermocouple positions, and [0,
1].

The interpolated temperature function u ^* (x, y, t) is described by equation (4) using a basis function φ described later.

The coefficient λ _j is determined by solving the matrix equation (5). Here, A is (m + 1) × (m + 1)
) Matrix, b is an (m + 1) vector. x _k , x _s , t _k , and t _s are definition points of the information amount in the region of the temperature measurement data collection point. On the other hand, x _j and t _j are the coordinates of the reference point on the spatio-temporal coordinate called the center point, and usually the same point as the definition point of the information amount may be adopted.

  Next, the basis function φ is defined as in equations (6) and (7) using a basic solution format that satisfies equation (1).

Here, T is a parameter for adjusting the diffusion profile of the basic solution, and H (t) is a snake side function. The y-direction component q _y of the heat flux on the operating surface can be calculated by equation (8). k is the thermal conductivity of the mold material.

In the actual machine, the molten metal level was detected by the method of the present invention, and compared with the molten metal level detected by the existing method and the measured molten metal level. In this comparison, a plurality of thermocouples 6 are arranged and embedded in the casting direction of the mold short side.
In the method of the present invention, as shown in FIGS. 5C and 5D, the vector component value in the casting direction of the heat flux on the working surface is calculated, and the position where it becomes the maximum is determined as the molten metal level. FIG. 5C shows the temperature distribution in the mold 1 (the darker the dot, the higher the temperature) and the heat flux on the operating surface. In FIG.5 (d), the vector component value of the casting direction of the heat flux in an operation surface is shown.

  On the other hand, in the existing method, as shown in FIG. 5B, the temperature distribution in the mold 1 is calculated, and the position where the maximum temperature × 0.65 is determined as the hot water level based on the empirical rule.

  Further, as shown in FIG. 6, a float 501 is floated on the hot water surface, and a rod 502 is provided on the float 501. In addition, an oscillation measurement jig 503 is set. Then, the movement of the tip of the rod 502 and the tip of the oscillation measurement hardware were photographed by the video camera 504, and the vertical surface level was measured by digitizing and recording the displacement in the vertical direction by image processing.

FIG. 7 shows the molten metal level detected by the method of the present invention, the molten metal level detected by the existing method, and the measured molten metal level. The horizontal axis represents time, and the vertical axis represents the hot water level.
In the existing method, when the measured hot water level becomes high, the detection accuracy is extremely lowered, and the measured value cannot be tracked.
On the other hand, it can be seen that the measured values can be tracked over a wide range in the method of the present invention. Considering that there is a variation in the measured accuracy of the molten metal level of about 5-10 mm, it can be said that the molten metal level detected by the method of the present invention has a good correspondence with the measured molten metal level.

  As described above, since the hot water level is detected by detecting the influence of heat transfer at the hot water surface position of heat removal by powder, the detection accuracy of the hot water level can be improved.

(About processing of the control unit 104)
FIG. 8 shows control processing executed by the control unit 104.
In step S <b> 801, the control unit 104 acquires a hot water surface profile from the hot water surface profile measuring unit 103.
In step S802, the control unit 104 determines whether or not the difference between the maximum value and the minimum value in the molten metal surface profile acquired in step S801 exceeds a predetermined value, in this example, 15 mm. If it exceeds 15 mm, it is determined that it is necessary to eliminate the difference in molten metal level, and the process proceeds to step S803. If it is 15 mm or less, the process is exited.
In step S803, the control unit 104 decreases the casting speed. In the present embodiment, the casting speed is reduced by 10% or more from the current casting speed. By reducing the casting speed, it is possible to eliminate the level difference of the molten metal surface.

FIG. 9 shows a control process executed by the control unit 104 when the casting speed is reduced in step S803 of FIG.
In step S <b> 901, the control unit 104 acquires a hot water surface profile from the hot water surface profile measuring unit 103.
In step S902, the control unit 104 determines whether or not the difference between the maximum value and the minimum value in the molten metal surface profile acquired in step S901 is a predetermined value, which is 15 mm or less in this example. If it is 15 mm or less, it is determined that the molten metal surface height difference has been eliminated, and the process proceeds to step S903. If it exceeds 15 mm, it is determined that a difference in level of the hot water surface has occurred, and the present process is exited.
In step S903, the control unit 104 returns the current casting speed to the casting speed before being decreased in step S803.

Here, in the present embodiment, the threshold value of the molten metal surface height difference is set to 15 mm, and the reduction rate of the casting speed is set to 10% or more, which is based on the knowledge obtained from the results.
Table 1 shows the height difference and the breakout alarm occurrence rate. The breakout alarm occurrence rate is defined as the number of occurrences per 350T of molten steel. A vertical axis | shaft shows a metal surface level difference and a horizontal axis shows a casting speed. Here, it is assumed that the range in which the breakout alarm occurrence rate exceeds 1.0% is an unacceptable range (the white range in the figure). Casting conditions are: casting thickness: 250 mm, casting width: 1250 mm, mold upper end to molten metal surface position: 100 mm, steel type: low-carbon AL-K steel, electromagnetic stirring: application (100 mmFe). In addition, the range shown by-shows that the hot_water | molten_metal surface fluctuation | variation did not arise at this casting speed under this casting condition.

It is assumed that the normal casting speed is 1.20 mpm. When the casting speed is 1.20 mpm, if the molten metal surface height difference exceeds 15 mm, the breakout alarm occurrence rate is in an unacceptable range. In this case, when the casting speed is reduced to 1.08 mpm (decrease of 10.0%), it can be seen that the breakout alarm occurrence rate falls within the allowable range. This shows that it is preferable to reduce the casting speed by 10% or more.
Moreover, when the molten metal surface level difference exceeds 20 mm, even if the casting speed is reduced to 1.08 mpm (decrease of 10.0%), the breakout alarm occurrence rate remains in an unacceptable range, and the casting speed is reduced. It can be seen that when it is reduced to 0.96 mpm (a decrease of 20.0%), the breakout alarm occurrence rate falls within the allowable range. Therefore, in parallel with the control described with reference to FIG. 8, when the molten metal surface level difference exceeds 20 mm, the casting speed may be controlled to be reduced by 20% or more.

  As described above, the detection accuracy of the molten metal level is improved by detecting the molten metal level by detecting the influence of the heat transfer at the molten metal surface position, and the measurement accuracy of the molten metal surface profile in the mold is improved for stable operation. Can be realized.

[Second Embodiment]
The second embodiment is an example in which the processing of the control unit 104 is changed from the first embodiment. In the following, description of points common to the first embodiment will be omitted, and differences from the first embodiment will be mainly described.

(About processing of the control unit 104)
FIG. 10 shows control processing executed by the control unit 104.
In step S <b> 1001, the control unit 104 acquires a hot water surface profile from the hot water surface profile measuring unit 103.
In step S1002, the control unit 104 determines whether or not the difference between the maximum value and the minimum value in the molten metal surface profile acquired in step S1001 exceeds a predetermined value, in this example, 15 mm. If it exceeds 15 mm, it is determined that it is necessary to eliminate the difference in molten metal level, and the process proceeds to step S1003. If it is 15 mm or less, the process is exited.
In step S1003, the control unit 104 decreases the electromagnetic stirring thrust of the electromagnetic stirring device 7. In the present embodiment, the electromagnetic stirring thrust is reduced by 20% or more than the current electromagnetic stirring thrust. By reducing the electromagnetic stirring thrust, the difference in molten metal level can be eliminated.

FIG. 11 shows a control process executed by the control unit 104 when the electromagnetic stirring thrust is reduced in step S1003 of FIG.
In step S <b> 1101, the control unit 104 acquires a hot water surface profile from the hot water surface profile measuring unit 103.
In step S1102, the control unit 104 determines whether or not the difference between the maximum value and the minimum value in the molten metal surface profile acquired in step S1101 is a predetermined value, which is 15 mm or less in this example. If it is 15 mm or less, it is determined that the molten metal surface height difference has been eliminated, and the process proceeds to step S1103. If it exceeds 15 mm, it is determined that a difference in level of the hot water surface has occurred, and the present process is exited.
In step S1103, the control unit 104 returns the current electromagnetic stirring thrust to the electromagnetic stirring thrust before being decreased in step S1003.

Here, in this embodiment, the threshold value of the molten metal surface height difference is set to 15 mm, and the reduction rate of the electromagnetic stirring thrust is set to 20% or more. This is based on knowledge obtained from actual results.
Table 2 shows the height difference and the breakout alarm occurrence rate. The breakout alarm occurrence rate is defined as the number of occurrences per 350T of molten steel. A vertical axis | shaft shows a molten metal surface level difference, and a horizontal axis shows electromagnetic stirring thrust. Here, it is assumed that the range in which the breakout alarm occurrence rate exceeds 1.0% is an unacceptable range (the white range in the figure). The casting conditions are casting thickness: 250 mm, casting width: 1250 mm, mold upper end to molten metal surface position: 100 mm, casting speed: 1.20 mpm, steel type: low-char AL-K steel. In addition, the range shown by-shows that the molten metal surface fluctuation | variation did not arise with this electromagnetic stirring thrust under this casting condition.

The normal electromagnetic stirring thrust is assumed to be 100 mmFe. When the electromagnetic stirring thrust is 100 mmFe, if the molten metal surface height difference exceeds 15 mm, the breakout alarm occurrence rate is in an unacceptable range. In this case, when the electromagnetic stirring thrust is reduced to 80 mm Fe (20% reduction), it can be seen that the breakout alarm occurrence rate falls within the allowable range. This indicates that it is preferable to reduce the electromagnetic stirring thrust by 20% or more.
In addition, if the molten metal surface height difference exceeds 20 mm, even if the electromagnetic stirring thrust is reduced to 80 mm Fe (20% reduction), the breakout alarm occurrence rate remains in an unacceptable range, and the electromagnetic stirring thrust is reduced to 60 mm Fe. It can be seen that when it is reduced (a 40% reduction), the breakout alarm rate is within an acceptable range. Therefore, in parallel with the control described with reference to FIG. 10, when the molten metal surface height difference exceeds 20 mm, control may be performed to reduce the electromagnetic stirring thrust by 40% or more.

As mentioned above, although this invention was demonstrated with various embodiment, this invention is not limited only to these embodiment, A change etc. are possible within the scope of the invention.
The molten metal surface profile measuring device in the continuous casting mold to which the present invention is applied can be realized by a computer device including, for example, a CPU, a ROM, a RAM, and the like.
In addition, the present invention supplies software (program) for realizing a molten metal surface profile measurement function in a continuous casting mold to a system or apparatus via a network or various storage media, and the computer of the system or apparatus reads the program. It can also be realized by executing.

  1: continuous casting mold, 2a, 2b: mold short side, 3a, 3b: mold long side, 4: immersion nozzle, 5: molten metal surface, 6: thermocouple, 7: electromagnetic stirring device, 100: control device for continuous casting , 101: input unit, 102: calculation unit, 103: hot water surface profile measurement unit, 104: control unit

Claims (9)

A method for measuring a molten metal surface profile in a continuous casting mold,
An acquisition step of acquiring measurement values of a plurality of temperature detection means arranged and embedded in the casting direction at a plurality of positions in the width direction of the mold long side and / or the width direction of the mold short side of the continuous casting mold;
A calculation step for solving a heat transfer inverse problem using the measurement value of the temperature detection means acquired in the acquisition step and calculating a component value in the casting direction of the heat flux on the working surface at the plurality of positions;
Based on the component value in the casting direction of the heat flux at the working surface at the plurality of positions calculated in the calculation step, the molten metal surface profile is measured by detecting the surface level at the plurality of positions. And a step of measuring a molten metal surface profile in a continuous casting mold.   In the molten metal surface profile measuring step, the position where the component value in the normal direction of the molten metal surface that is opposite to the casting direction of the heat flux in the working surface at the plurality of positions calculated in the calculating step is maximized. The molten metal surface profile measuring method in the continuous casting mold according to claim 1, wherein the level is determined as a level.   3. The continuous casting mold according to claim 1, wherein a plurality of temperature detection means are arranged and embedded in a casting direction at a pair of mold short sides and a pair of mold long sides of the continuous casting mold. No hot water profile measurement method.   The casting speed is reduced when the difference between the maximum value and the minimum value in the molten metal profile obtained by the molten metal profile measurement method in the continuous casting mold according to any one of claims 1 to 3 exceeds a predetermined value. A control method for continuous casting, characterized by comprising:   5. The continuous casting control method according to claim 4, wherein when the difference between the maximum value and the minimum value in the molten metal surface profile exceeds 15 mm, the casting speed is reduced by 10% or more.   When the difference between the maximum value and the minimum value in the molten metal profile obtained by the molten metal profile measuring method in the continuous casting mold according to any one of claims 1 to 3 exceeds a predetermined value, the electromagnetic stirrer A control method for continuous casting, characterized by reducing electromagnetic stirring thrust.   The continuous casting control method according to claim 6, wherein when the difference between the maximum value and the minimum value in the molten metal surface profile exceeds 15 mm, the electromagnetic stirring thrust is reduced by 20% or more. A hot water surface profile measuring device in a continuous casting mold,
Input means for inputting measured values of a plurality of temperature detection means arranged and embedded in the casting direction at a plurality of positions in the width direction of the mold long side and / or the width direction of the mold short side of the continuous casting mold,
Solving the inverse heat transfer problem using the measured value of the temperature detecting means input by the input means, calculating means for calculating the component value in the casting direction of the heat flux at the working surface at the plurality of positions;
Based on the component value in the casting direction of the heat flux at the operating surface at the plurality of positions calculated by the calculating means, the molten metal level profile is detected by detecting the level of the molten metal level at the plurality of positions. An apparatus for measuring a molten metal surface profile in a continuous casting mold, comprising a measuring means. A program for measuring a molten metal surface profile in a continuous casting mold,
A process of inputting measured values of a plurality of temperature detecting means arranged and embedded in the casting direction at a plurality of positions in the width direction of the mold long side and / or the width direction of the mold short side of the continuous casting mold,
Processing to solve the inverse heat transfer problem using the input measurement value of the temperature detection means, and calculate the component value in the casting direction of the heat flux at the working surface at the plurality of positions;
Based on the calculated component value in the casting direction of the heat flux on the working surface at the plurality of positions calculated, the computer detects the surface level at the plurality of positions and measures the surface profile. Program to let you.

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