JP3508420B2 - Method of controlling molten steel flow in continuous casting mold of steel - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for controlling the flow of molten steel in a continuous casting mold for steel.

[0002]

2. Description of the Related Art In a continuous casting method for steel, the flow of molten steel in a mold due to the discharge flow of molten steel injected into a mold through an immersion nozzle has a great influence on the surface properties and internal properties of a cast slab. If the surface velocity of the molten steel is too fast or a vertical vortex is generated on the molten metal surface in the mold (hereinafter referred to as "meniscus"), the mold powder added on the meniscus is caught in the molten steel, which is fatal in the product. Since it causes various defects, the flow of molten steel in the meniscus is particularly emphasized.

Therefore, as an important subject for improving the quality of the slab, a number of methods for controlling the flow of the meniscus by improving the shape of the immersion nozzle and utilizing electromagnetic force have been proposed.

JP-A-63-16840 (hereinafter, referred to as
“Prior Art 1”) has means for applying an electromagnetic force in the flow direction of the discharge flow from the immersion nozzle or in the opposite direction, and has a molten steel density ρ, a discharge flow Q of molten steel from the immersion nozzle, and a molten steel. Collision velocity V and collision angle θ when the flow collides with the mold,
And the distance D from the meniscus where the molten steel flow collides
There is disclosed a method of controlling the applied electromagnetic force so that the fluctuation index R falls within the range of 1 to 10 by defining the fluctuation index R of the following formula (1) as a function of

R = ρQV (1−sinθ) / (4D) (1) Temporary stores and others are based on materials and processes “Vol.5 (1992),
p996 ”(hereinafter referred to as“ prior art 2 ”),
Assuming that A is a constant, the molten steel surface flow velocity index M of the following equation (2) is determined as a function of the slab drawing speed V, the immersion nozzle discharge angle θ, the immersion nozzle immersion depth d, and the mold width L. It is disclosed that the defect index of the product is lowered by applying the static magnetic field to the discharge flow in the region where the index M is high.

M = AVcos θ (1-sin θ) ^1/2 / (d + Ltan θ / 2) ^1/2 (2) Further, Japanese Patent Laid-Open No. 7-47452 (hereinafter referred to as “Prior Art 3”) , A method for controlling the operating method based on real-time patterned intermediate indicators of operating conditions based on information detected by various sensors arranged in a tundish, an immersion nozzle, or a mold is disclosed. .

[0007]

Both the formulas disclosed in Prior Art 1 and Prior Art 2 improve the quality of the cast product as an index for preventing an increase in the surface flow velocity of the molten steel in the mold due to the increase in the speed of drawing the cast product. Has been effective. However, these indicators alone are not always sufficient to meet the stricter demands on quality in recent years.

The inventors have examined Prior Art 1 and Prior Art 2 based on actual machine measurement results, model experiment results, and numerical analysis results, and found that Prior Art 1 and Prior Art 2 have the following problems. And (1) The effect of Ar gas on the flow of molten steel in the mold is not taken into consideration, and even if it is taken into consideration, it is underestimated. (2) The effect on the molten steel flow when applying electromagnetic force has not been evaluated. (3) As a result of these, the flow pattern of molten steel in the mold is premised on a pattern in which the discharge flow reaches the solidification shell on the short side of the mold and collides with it, and then separates into an upflow and a downflow, which will be described later. No other flow patterns are considered.

By the way, in the continuous casting method of steel, Ar gas is blown into the immersion nozzle in order to prevent nozzle clogging due to adhesion of alumina to the immersion nozzle. After cleaning the inside of the immersion nozzle, this Ar gas flows into the mold together with the discharge flow, and becomes bubbles and floats on the meniscus. The influence of the Ar gas bubbles on the molten steel flow is extremely difficult to estimate, and therefore is not considered in the equations (1) and (2).

The inventors conducted a water model experiment under the conditions in which the volume change due to the thermal expansion of Ar gas was taken into consideration and the method of blowing Ar gas was variously changed. As a result, the influence of Ar gas on the flow of molten steel in the mold is extremely large, and the surface flow velocity changes significantly depending on the Ar gas flow rate and Ar gas bubble diameter, and the flow pattern of molten steel in the mold itself deviates from the above flow pattern. It became clear.

Similarly, it was confirmed that even when an electromagnetic force was applied, the flow pattern of the molten steel in the mold was changed by changing the magnetic field strength.

As described above, in order to improve the quality of the slab, it is necessary to control in consideration of the change in the flow pattern of the molten steel in the mold due to the influence of Ar gas and electromagnetic force, which is considered in Prior Art 1 and Prior Art 2. Not not.

Further, the prior art 3 is excellent in that the flow state of the molten steel in the mold can be displayed on the display in real time and can be immediately fed back to the operation. However, the discharge velocity of the molten steel from the immersion nozzle and the surface velocity of the molten steel are excellent. However, it shows only drifts on the left and right of the mold, and does not cover changes in the flow pattern of molten steel in the mold.

The present invention has been made on the basis of the above-mentioned phenomenon. An object of the present invention is to set a flow pattern of molten steel in a continuous casting mold to an appropriate predetermined pattern, and to select a casting condition that gives the predetermined pattern. It provides a means for doing so.

[0015]

A molten steel flow control method in a continuous casting mold for steel according to the invention of claim 1 is such that Ar gas is blown into molten steel in a dipping nozzle and the molten steel is discharged from the dipping nozzle. When injecting molten steel into the mold while applying a magnetic field for continuous casting, four conditions are considered as casting conditions: mold size, slab drawing speed, amount of Ar gas blown into the immersion nozzle, and magnetic field strength. , The molten steel flow pattern in the mold is measured in advance in a plurality of casting conditions consisting of these elements, and the molten steel flow pattern in the mold in the individual casting conditions is estimated based on the measurement result so that the predetermined flow pattern is obtained. It is characterized in that the strength of the magnetic field applied to the discharge flow or the amount of Ar gas blown into the immersion nozzle is adjusted.

Further, in the molten steel flow control method in the continuous casting mold for steel according to the invention of claim 2, Ar gas is blown into the molten steel in the immersion nozzle, and a magnetic field is applied to the molten steel discharge flow from the immersion nozzle. Meanwhile, when injecting molten steel into the mold for continuous casting, the casting conditions include the mold size, the slab drawing speed, the amount of Ar gas blown into the immersion nozzle, and the magnetic field strength. The molten steel flow pattern in the mold and the surface flow velocity are measured in advance under a plurality of casting conditions, and the flow pattern and the surface flow velocity of the molten steel in the mold under the individual casting conditions are estimated based on the measurement results, and a predetermined flow pattern is obtained. Further, the magnetic field strength applied to the discharge flow or the amount of Ar gas blown into the immersion nozzle is adjusted so as to obtain a predetermined surface flow velocity.

According to the measurement results of the actual machine, the model experiment results, and the numerical analysis by the inventors, the flow pattern of the molten steel in the mold changes intricately due to the Ar gas bubbles floating in the mold and the influence of electromagnetic force application. By simplifying the flow pattern, it can be roughly divided into three patterns A, B, and C as shown in FIG.

In the pattern A, the discharge flow from the dipping nozzle reaches and collides with the solidified shell on the short side, and then rises up to the meniscus along the solidified shell on the short side, and then the meniscus from the short side. A flow pattern that separates into a flow that flows toward the immersion nozzle side and a flow that descends from the point of collision with the solidified shell on the short side toward the bottom of the mold. It is the flow pattern.

On the other hand, in the pattern B, due to the floating of Ar gas bubbles or the influence of electromagnetic force applied to the discharge flow, the discharge flow from the immersion nozzle does not reach the solidification shell on the short side of the mold, It is a flow pattern that is dispersed up to the solidified shell on the short side of the mold.

The pattern C is a flow pattern in which an ascending flow exists near the immersion nozzle, and appears mainly due to the floating of coarse Ar gas bubbles. In pattern C, a flow from the immersion nozzle to the short side of the mold is observed in the meniscus.

The situations in which these flow patterns appear will be described below. In FIG. 4, the horizontal axis represents the amount of Ar gas blown into the immersion nozzle, and the vertical axis represents the throughput (throughput is obtained as the product of the specific gravity of molten steel, the mold size, and the slab drawing speed, and is cast per unit time. (Which represents the weight of molten steel) and floats in the mold.
It is a schematic representation of how gas bubbles change.

When the throughput is high or the amount of Ar gas blown in is small, the Ar gas bubbles become finer, the volume ratio in the molten steel is small, and the influence on the molten steel flow is small. On the other hand, when throughput is low,
When the amount of Ar gas blown in is large, the Ar gas bubbles become large and the volume ratio of Ar gas in the molten steel also becomes large, changing the flow pattern of the molten steel in the mold. Particularly when coarse Ar gas bubbles are generated, an upward flow is formed in the vicinity of the immersion nozzle, and the meniscus is disturbed by the floating Ar gas bubbles.

Based on these events, A into the immersion nozzle
FIG. 5 shows the generation distinction of the above-described three molten steel flow patterns in the mold, with the amount of r gas blown in and the throughput as factors.
The concept is shown in. As shown in FIG. 5, as the amount of Ar gas blown in increases, the effect of Ar gas bubbles increases, so the flow pattern of molten steel in the mold has a wider area of pattern C, and as the throughput increases, pattern A increases. Area becomes wider, and the pattern B becomes an area where the boundary between the pattern A and the pattern C is limited.

Similarly, the flow patterns can be distinguished on the coordinate plane with the magnetic field strength and the throughput as factors and the abscissa and the ordinate as the factors. FIG. 6 shows an example of the distinction obtained from the actual measurement and the numerical analysis. Figure 6
The case where a moving magnetic field method capable of applying a magnetic field strength of up to 2000 gauss is applied is shown. The "positive" side of the abscissa sign is the direction in which the moving direction of the magnetic field slows the discharge flow, and the "negative" side is the discharge flow. Is the direction to accelerate. As shown in FIG. 6, when the throughput is small, the pattern C is set, and when the throughput is large, the pattern A is set. Further, the pattern B becomes wider in the region of the boundary between the pattern A and the pattern C as the magnetic field strength for decelerating the discharge flow velocity becomes larger, but the pattern B does not exist when the magnetic field strength for accelerating the discharge flow is large. Range occurs. Thus, it can be seen that the pattern B is formed in a limited range.

The amount of mold powder defects in the product was investigated for each flow pattern of molten steel in the mold.
FIG. 7 shows the result of the survey. As shown in FIG. 7, it was found that when the flow pattern of the molten steel in the mold was pattern B, there were few mold powder defects and 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 likely to occur in the meniscus between the center of the mold and a position 1/4 of the width of the mold away from the center of the mold. 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.
Further, in the case of pattern C, the upward flow of molten steel near the immersion nozzle and the floating coarse Ar gas bubbles cause fluctuations / disturbance of the meniscus, mixing of mold powder occurs, and the surface velocity of molten steel is high. In this case, a vertical vortex is generated near the short side of the mold, which causes mixing of mold powder. On the other hand, in the case of pattern B,
This is because there is no generation of vortices in the meniscus or appearance of a strong surface flow, and the flow conditions are such that entrapment of mold powder is unlikely to occur.

Also, in the pattern B, it was found that the product defect occurrence index is particularly low when the molten steel surface flow velocity is 0.1 m / sec or less in the entire meniscus range.

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 product deterioration rate, and improve the slab care-free rate. . At that time, the molten steel surface flow velocity was further reduced to 0.
When it is 1 m / sec or less, the product defect occurrence index can be stably suppressed to a low value, which is more preferable. The flow direction of the molten steel surface flow may be from the short side of the mold to the immersion nozzle side or vice versa.
Setting the speed to 1 m / sec or less means that the absolute value of the flow velocity is 0.1
It means to be less than m / sec.

However, as described above, the flow pattern of the molten steel in the mold is complicated with many influencing factors such as various casting conditions, Ar gas bubbles, electromagnetic force, etc., and therefore cannot be expressed by a simple index. .

Therefore, the inventors decided to control by the following method. First, as casting conditions, four elements of mold size, slab withdrawal speed, Ar gas blowing amount into the immersion nozzle, and magnetic field strength are targeted, and molten steel in a mold is preliminarily prepared under a plurality of casting conditions including combinations of these elements. The flow pattern, as well as the surface flow velocity, is measured to systematize the flow data of molten steel in the mold.

Then, based on this systematized measurement result, the flow pattern under the individual casting conditions, and further the surface flow velocity are estimated, and the estimated flow pattern and the predetermined flow pattern,
By comparing the estimated surface flow velocity with a predetermined surface flow velocity, and adjusting the magnetic field strength applied to the discharge flow or the amount of Ar gas blown into the immersion nozzle, the molten steel flow in the mold has a predetermined flow pattern, and further A method of setting a predetermined surface flow velocity was adopted.

[0032]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described with reference to the drawings.
FIG. 1 is a flow chart of the present invention, and FIG. 2 is a schematic side sectional view of a mold part of a continuous casting machine having a rectangular cast piece cross section to which the present invention is applied.

In FIG. 2, a long side 2 of the opposite mold and a short side 3 of the opposite mold 3 slidably mounted in the long side 2 of the mold.
Above the mold 1 composed of and, the tundish 1
0 is placed. A sliding nozzle 11 is arranged at the bottom of the tundish 10, and a rectifying nozzle 14 and a dipping nozzle 4 are sequentially arranged on the lower surface side of the sliding nozzle 11 to form an outflow hole 15 from the tundish 10 to the mold 1. The tundish 10 receives the molten steel 6 from a ladle (not shown), immerses the discharge hole 9 provided in the lower part of the immersion nozzle 4 in the molten steel 6 in the mold 1, and discharges the discharge flow 7 from the discharge hole 9 into the mold short side 3 The molten steel 6 is poured into the mold 1. The molten steel 6 is cooled in the mold 1 to form a solidified shell 16, which is drawn below the mold 1 to form a cast piece.

An Ar gas introduction pipe 5 is connected to the immersion nozzle 4, and an outflow hole 15 of the immersion nozzle 4 from the Ar gas introduction pipe 5 is connected.
Ar gas is blown into the inside. The blown Ar gas flows into the mold 1 together with the molten steel 6 through the immersion nozzle 4 and the discharge hole 9, floats on the meniscus 13 through the molten steel 6 in the mold 1, and is added to the meniscus 13. It penetrates the powder 12 and reaches the atmosphere.

On the back surface of the long side 2 of the mold, an electromagnetic coil 8 for magnetically braking the discharge flow 7 is installed so that the center position of the electromagnetic coil 8 in the casting direction is below the lower end position of the discharge hole 9.
The electromagnetic coil 8 facilitates flow control of molten steel,
It is desirable that the dipping nozzle 4 is divided into left and right parts in the width direction of the mold 1 so that power can be independently applied to the left and right parts. The magnetic field generated from the electromagnetic coil 8 may be either a moving magnetic field in which the magnetic field moves or a fixed magnetic field in which the magnetic field is fixed. The moving magnetic field has a feature that it can decelerate and accelerate the molten steel flow, and either the moving magnetic field or the fixed magnetic field may be appropriately selected from the casting conditions, the mold type and the like.

The application of the present invention to the continuous casting machine having such a structure will be described below with reference to the flow chart shown in FIG.

First, under various casting conditions, the molten steel surface flow velocity in the mold 1, the molten metal surface fluctuation amount, and the Ar gas levitation distribution of the meniscus 13 are measured.

The molten steel surface flow velocity is measured by immersing a refractory rod in the meniscus 13 from the deflection angle or directly by using electromagnetic force. The Ar gas levitation distribution of an optical distance meter or the like can be measured by a method in which a gas sampling tube is installed directly above the meniscus 13 and gas analysis is performed. When the floating amount of Ar gas of the meniscus 13 is large in the vicinity of the dipping nozzle 4, the flow pattern of the molten steel in the mold is pattern C, when it is large on the mold short side 3 side, it is pattern A, and when it is uniform, it is pattern B. The Ar gas levitation distribution of 13 is a means to indirectly measure the flow pattern of molten steel in the mold.

As the casting conditions, there are four factors, that is, the mold size, the slab drawing speed, the amount of Ar gas blown into the immersion nozzle 4, and the magnetic field strength, and these factors are changed and measured. The mold size and the slab drawing speed can be summarized as a throughput.

Further, the immersion nozzle type, the brick conditions for blowing Ar gas (for example, the porosity and the pore diameter of the porous brick or the pore diameter and the number of the through holes), and the mold powder conditions (for example, high viscosity and low crystallization temperature). If there is a change, measure the data and collect the data.
Here, the immersion nozzle type means the sectional shape of the immersion nozzle 4,
It shows the inner diameter, the discharge angle of the discharge hole 9, the immersion depth, the discharge hole area, and the outflow hole bottom shape.

In this way, various casting conditions and measurement data (molten steel surface flow velocity, molten metal surface fluctuation, Ar gas levitation distribution, flow pattern) corresponding to the casting conditions were input to the computer as a mold flow database. Remember.
Further, the quality information of the obtained slab is also stored in the computer at the same time, thus systematizing the flow data of the molten steel in the mold. The flow pattern of the molten steel in the mold can be accurately determined by numerically analyzing the measurement data of the Ar gas levitation distribution and the molten steel surface flow velocity.

Prior to individual casting, individual casting conditions are input to a computer to estimate the flow pattern and the surface flow velocity under the casting conditions. When the estimated flow pattern or the surface flow velocity is different from the predetermined flow pattern or the predetermined surface flow velocity, the magnetic field strength or the Ar gas injection amount is changed and input to the computer again, and then the flow pattern and the surface flow velocity To estimate. In this way, the magnetic field strength or Ar is adjusted so that the flow pattern of the molten steel in the mold is pattern B, and further, the molten steel surface flow velocity is 0.1 m / sec or less.
By changing the gas blowing amount, the magnetic field strength or the Ar gas blowing amount satisfying these conditions is obtained and presented.

After the magnetic field strength or the amount of Ar gas blown in is adjusted, individual casting is started. The magnetic field strength is adjusted by changing the current or voltage applied to the electromagnetic coil 8, and the Ar blowing amount is adjusted by a normal flow rate adjusting valve.

The position of the Ar gas blown into the immersion nozzle 4 may be the sliding nozzle 11 installed on the immersion nozzle 4 or the stopper tip in the case of a stopper type opening / closing device. It doesn't hurt at all.

[0045]

EXAMPLE An example of the present invention using the continuous casting machine having the structure shown in FIG. 2 will be described below. [Embodiment 1] The cross section of the mold has a thickness of 220 mm and a width of 12
An ultra-low carbon Al killed steel was cast at a slab drawing speed of 2.5 m / min with a slab continuous casting machine of 00 mm. On the back surface of the long side of the mold, an electromagnetic coil divided into two in the width direction of the mold was installed. The center position of the electromagnetic coil in the casting direction is 150 mm below the lower end of the immersion nozzle discharge hole. A moving magnetic field is generated by this electromagnetic coil, a moving magnetic field of up to 2000 gauss can be applied to the discharge flow, and the moving direction of the magnetic field can be from the mold short side to the immersion nozzle side or vice versa. Moreover, the magnetic field can be applied independently to the left and right.

The dipping nozzle used has a circular cross section,
Inner diameter 85 mm, discharge angle downward 25 degrees, immersion depth (distance from meniscus to upper end of discharge hole) 230 mm, discharge hole diameter 85 mm, outlet hole bottom shape as shown in FIG. is there.

The throughput at this time is 4.6 ton /
min, Ar gas 9 Nl / mi in the immersion nozzle
I blew it.

FIG. 8 shows an example of the database under this casting condition. Throughput 4.6 ton / min
In order to realize a flow pattern of pattern B and a molten steel surface flow velocity of 0.1 m / sec or less, it was estimated that the magnetic field strength of the electromagnetic coil must be set to 60% or more. Cast as%. In FIG. 8, the “positive” side of the horizontal axis is the direction in which the magnetic field moves in the direction in which the discharge flow is decelerated, and the “negative” side is the direction in which the discharge flow is accelerated. The numbers in the figure indicate the molten steel in the meniscus. In the surface flow velocity value, the sign "positive" indicates a flow from the mold short side toward the immersion nozzle, and "negative" indicates a flow in the opposite direction. The molten steel surface flow velocity tends to increase toward the “positive” side as the flow pattern co-magnetic field strength index toward the “negative” side.

After casting, the slab was rolled into a thin steel plate, and the thin steel plate was subjected to an ultrasonic flaw detection test to examine defects caused by the mold powder. As a result, the defect occurrence rate was 0.2%, and no magnetic field was applied. It was possible to significantly reduce defects as compared with the defect occurrence rate of 1.6% under the casting conditions.

[Embodiment 2] The dimension of the mold cross section is 250 in thickness.
mm, width 2,000 mm, slab continuous casting machine, low carbon Al killed steel was cast at a slab drawing speed of 1.6 m / min. On the back surface of the long side of the mold, an electromagnetic coil divided into two in the width direction of the mold was installed. The center position of the electromagnetic coil in the casting direction is 150 mm below the lower end of the immersion nozzle discharge hole. With this electromagnetic coil, a 1000 Gauss moving magnetic field moving from the short side of the mold to the dipping nozzle side was applied to perform casting while decelerating the discharge flow. The immersion nozzle used is of the same type as in Example 1. The throughput at this time is 5.
It is 6 ton / min.

FIG. 9 shows an example of the database under this casting condition. Under this casting condition, as shown in FIG.
It was estimated that the flow pattern of the molten steel in the mold was pattern C when the Ar gas blowing amount was 10 Nl / min, and the pattern B was when the Ar gas blowing amount was 6 Nl / min.

Therefore, the amount of Ar gas blown is 6 Nl / mi.
n (Example) and 10 Nl / min (Comparative Example) were cast at two levels, a refractory rod was immersed in a meniscus to measure the molten steel surface flow velocity, and at the same time, the Ar gas levitation state at the meniscus was investigated.

FIG. 10 shows the results of measuring the Ar gas levitation state at the meniscus. Ar gas blowing amount is 10Nl
In the case of / min, it was confirmed that a large amount of Ar gas floated in the vicinity of the immersion nozzle, and the flow pattern of the molten steel in the mold was confirmed to be pattern C. In contrast,
When the amount of Ar gas blown is 6 Nl / min, the amount of floating Ar gas at the position separated from the dipping nozzle to the short side of the mold by 1/4 of the mold width is slightly large, but it is almost uniform in the entire width direction. Yes, the flow pattern of molten steel in the mold is pattern B
Was confirmed.

As a result of investigating the defect occurrence rate by the ultrasonic flaw detection test in the thin steel sheet when the Ar gas blowing amount was 6 Nl / min and 10 Nl / min, the Ar gas blowing amount was 6 Nl / min. In this case, the defect occurrence rate was 0.1%, which was a good result, but 10 Nl /
In the case of min, the defect occurrence rate was 1.3%, which was not much different from the case where no magnetic field was applied.

[0055]

According to the present invention, the flow pattern of the molten steel in the mold and the surface velocity of the molten steel can be optimized under various casting conditions, so that a continuously cast slab of excellent quality can always be stably produced. You can

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a flow of the present invention.

FIG. 2 is a view showing a schematic side sectional view of a casting mold part of a continuous casting machine having a rectangular cast piece section to which the present invention is applied.

FIG. 3 is a diagram schematically showing three types of flow patterns of molten steel in a continuous casting mold.

FIG. 4 is a diagram schematically showing the influence of the amount of Ar gas blown into the immersion nozzle and the throughput on the shape of Ar gas bubbles.

FIG. 5 is a diagram conceptually showing the division of the molten steel flow pattern in the mold with the amount of Ar gas blown into the immersion nozzle and the throughput as factors.

FIG. 6 shows the magnetic field strength index and the throughput as factors.
It is the figure which showed an example of the division of the flow pattern of the molten steel in a mold calculated | required by numerical analysis.

FIG. 7 is a diagram showing a comparison of defective occurrence indexes in products for each flow pattern of molten steel in a mold.

FIG. 8 is a diagram showing an example of a database under casting conditions in Example 1 of the present invention.

FIG. 9 is a diagram showing an example of a database under casting conditions in Example 2 of the present invention.

FIG. 10 is a diagram showing a comparison of Ar gas levitation distributions in a meniscus when the molten steel flow in the mold is pattern B and pattern C.

[Explanation of symbols]

1; mold 2; Mold long side 3; mold short side 4; immersion nozzle 5; Ar gas introduction pipe 6; Molten steel 7: Discharge flow 8; Electromagnetic coil 9; Discharge hole 10; Tundish 11; sliding nozzle 12; Mold powder 13; Meniscus 14; rectifying nozzle 15; Outflow hole 16; Solidified shell

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noriko Kubo 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (56) Reference JP 10-193047 (JP, A) JP 10 -263777 (JP, A) JP 63-104758 (JP, A) JP 10-5957 (JP, A) JP 6-15420 (JP, A) (58) Fields investigated (Int.Cl) . ⁷ , DB name) B22D 11/103 B22D 11/04 311 B22D 11/10 360 B22D 11/18

Claims (2)

(57) [Claims] 1. A mold size is used as a casting condition when Ar gas is blown into the molten steel in the immersion nozzle and the molten steel is injected into the mold while applying a magnetic field to the discharge flow of the molten steel from the immersion nozzle to perform continuous casting. , The slab drawing speed, the amount of Ar gas blown into the immersion nozzle, and the magnetic field strength are the four factors, and the flow pattern of molten steel in the mold is measured in advance under a plurality of casting conditions consisting of these factors. Estimating the flow pattern of the molten steel in the mold in the individual casting conditions based on, to adjust the magnetic field strength to be applied to the discharge flow or Ar gas blowing amount into the immersion nozzle so as to be a predetermined flow pattern, Method for controlling molten steel flow in a continuous casting mold for continuous steel. 2. A mold size as a casting condition when Ar gas is blown into the molten steel in the immersion nozzle and the molten steel is injected into the mold while applying a magnetic field to the discharge flow of the molten steel from the immersion nozzle to perform continuous casting. , The slab drawing speed, the amount of Ar gas blown into the dipping nozzle, and the magnetic field strength are targeted, and the flow pattern and the surface flow velocity of the molten steel in the mold are measured in advance under a plurality of casting conditions including these elements. , Estimating the flow pattern and the surface flow velocity of the molten steel in the mold under individual casting conditions based on the measurement results, and applying the magnetic field strength or the immersion nozzle to the discharge flow so that the predetermined flow pattern and the predetermined surface flow velocity are obtained. A method for controlling molten steel flow in a continuous casting mold for steel, comprising adjusting the amount of Ar gas blown into the steel.