JP4912945B2 - Manufacturing method of continuous cast slab - Google Patents

Description

  The present invention relates to a method for producing a continuous cast slab.

  Control of the flow of molten steel in a mold in continuous casting is an important technique for improving the surface quality and the internal part quality of a slab. In order to improve the quality of the slab surface, a technique is generally used in which an electromagnetic stirrer is installed at the upper part of the mold to flow the front of the solidified shell so that inclusions are not trapped in the solidified shell. .

  Here, in order to more effectively suppress trapping of inclusions, a control method for controlling the position of the liquid level of the molten steel so as to be within a range from the core center of the electromagnetic stirrer to the upper end of the core is disclosed. (For example, refer to Patent Document 1).

  On the other hand, in order to improve the internal parts of the slab, the discharge flow from the normally used immersion nozzle is braked by using an electromagnetic brake or the like such as a static magnetic field generator to prevent the discharge flow from entering the inside. A method for preventing intrusion of inclusions has been proposed.

  In order to achieve both the surface quality of the slab and the internal component level, it is not sufficient to control either the electromagnetic stirrer or the static magnetic field generator alone, so that both the surface quality and the internal component level are compatible. For this reason, a mold having both an electromagnetic stirrer and a static magnetic field generator is used (for example, see Patent Document 2).

JP 07-314104 A JP 2001-47195 A

  Due to the conflicting effect of stirring the molten steel and the brake effect on the discharge flow, if the brake effect is given priority, the stirring force in the mold will decrease and the slab surface quality will deteriorate. A phenomenon occurs in which the brake effect of the flow is lowered and the parts in the slab are deteriorated.

  However, a control method for improving the surface quality and the internal parts of the slab while utilizing the functions of both the electromagnetic stirrer and the static magnetic field generator to the maximum has not yet been established.

  Therefore, the present invention has been made in view of such problems, and the object thereof is to produce a new and improved continuous cast slab capable of further improving the surface quality and inner part quality of the slab. It is to provide a method.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research. As a result, in addition to the position of the liquid surface of the molten steel in the mold, the stirring force by the electromagnetic stirrer and the magnetic field strength by the static magnetic field generator are appropriately selected. It was conceived that the surface quality and the inner part quality of the slab can be further improved by controlling the slab.

  That is, in order to solve the above-mentioned problem, according to one aspect of the present invention, a downward discharge hole as a molten steel supply port for a continuous casting mold in which an electromagnetic stirring device is installed in the upper part and a static magnetic field generator is installed in the lower part Of the continuous cast slab that supplies molten steel through two immersion nozzles and controls the molten steel surface in the continuous casting mold so as to be positioned in the range from the center of the coil core of the electromagnetic stirrer to the upper end of the core. In the manufacturing method, the ratio of the stirring force by the electromagnetic stirrer on the surface of the molten steel and the magnetic field strength by the static magnetic field generator satisfies the following (Equation 1), and the static magnetic field generator at the position of the discharge hole: A method for producing a continuous cast slab in which the magnetic field strength according to satisfies the following (formula 2) is provided.

  Here, F is the stirring thrust [Pa] by the electromagnetic stirrer on the molten steel surface, and Bm is the magnetic field strength [Gauss] by the static magnetic field generator on the molten steel surface. The Bt is the magnetic field intensity [Gauss] by the static magnetic field generator at the position of the submerged nozzle discharge hole, and the Q is the throughput [ton / min].

  Moreover, it is good also considering the alternating current frequency of said electromagnetic stirring apparatus as 2 Hz-10 Hz.

  According to the present invention, it is possible to further improve the surface quality and inner part quality of a slab.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

(First embodiment)
(Construction of continuous casting machine)
The continuous casting machine according to the first embodiment of the present invention is supplied to a ladle (not shown) to which molten steel carried from a converter is supplied, and to a continuous casting mold 10 to be described later from the ladle. A tundish (not shown) that temporarily receives molten steel and removes inclusions such as oxides, and a continuous casting mold 10 to which molten steel is supplied from the tundish are provided.

  Below, the structure of the continuous casting mold 10 which concerns on this embodiment is demonstrated in detail, referring FIG. 1A and FIG. 1B. FIG. 1A is an explanatory view for explaining a longitudinal section of a continuous casting mold 10 according to the present embodiment, and FIG. 1B is a top view of the continuous casting mold 10 according to the present embodiment.

  As shown in FIG. 1A, the continuous casting mold 10 according to the present embodiment includes, for example, an immersion nozzle 20 that supplies molten steel, an electromagnetic stirring device 30, and a static magnetic field generation device 40.

  The continuous casting mold 10 is a container for solidifying a side surface of molten steel supplied from an immersion nozzle 20 described later to form a slab having a predetermined shape and feeding it from the bottom of the continuous casting mold 10. The continuous casting mold 10 is provided with an immersion nozzle 20 for supplying molten steel temporarily stored in the tundish.

  The immersion nozzle 20 has an upper end connected to the tundish, and supplies molten steel supplied from the tundish to the continuous casting mold 10. Under the immersion nozzle 20, diagonally downward discharge holes 22 that are molten steel supply ports to the continuous casting mold 10 are provided on the left and right. Molten steel supplied from the tundish is discharged from the left and right discharge holes 22 of the immersion nozzle 20 to the continuous casting mold 10 together with the inert gas. Although the discharge speed of molten steel can be controlled to an arbitrary value, for example, it is controlled to be about 1 to 2 m / sec. The immersion nozzle 20 is provided so that its height can be adjusted, and is controlled so that the discharge hole 22 of the immersion nozzle 20 is positioned below the molten steel surface 12 (also referred to as meniscus) in the continuous casting mold 10. Moreover, the discharge hole 22 needs to be provided so that it may be located between the electromagnetic stirring apparatus 30 and the static magnetic field generator 40 which are mentioned later.

  Inclusions 14 such as oxides present in the molten steel cause a decrease in the strength, workability, fatigue resistance, etc. of the steel material and surface flaws, and are thus possible in the continuous casting mold 10 until the molten steel is solidified. It must be lifted and removed as long as possible. In addition, since the components in the molten steel may be oxidized again, new inclusions may be entrained from slag mixed from the material that is missing or dissolved from the refractory of the continuous casting mold 10, It is necessary to lift and remove these new inclusions. In order to float such inclusions 14, the continuous casting mold 10 is provided with an electromagnetic stirring device 30 and a static magnetic field generation device 40.

  In order to prevent inclusion 14 from being trapped under the surface of the slab and becoming a product defect, an electromagnetic stirrer (In-mold Electromagnetic Stirrer: EMS) 30 changes the magnetic field in the molten steel in the continuous casting mold 10. The molten steel in the continuous casting mold 10 is agitated. As shown in FIG. 1B, the electromagnetic stirring device 30 is provided so as to surround the continuous casting mold 10 at a height near the meniscus of the continuous casting mold 10 and generates an electromagnetic stirring flow in the slab width direction in the molten steel. Moreover, it is necessary to control the molten steel surface 12 so that it may be located in the range of the upper end of a core from the coil center (core) of the electromagnetic stirring apparatus 30. In the continuous casting mold 10, solidification of the molten steel starts from a portion close to the inner wall of the continuous casting mold, and a solidified shell is generated. By stirring the molten steel with an electromagnetic stirring device, bubbles and inclusions 14 are formed on the solidified surface layer. Can be prevented from staying, and the surface quality of the slab can be improved.

  When the electromagnetic stirring device 30 is used alone, as shown in FIG. 1B, the electromagnetic stirring flow collides with the continuous casting mold to generate a downward flow, and the inclusion 14 is mixed into the slab. End up. Further, when the stirring force of the electromagnetic stirrer 30 is small, there is a problem that turbulent flow is generated in the vicinity of the continuous casting mold, and the inclusion 14 is captured in the vicinity of the inner wall of the continuous casting mold. For this reason, it is necessary to appropriately control the stirring force of the electromagnetic stirring device 30 and to use a static magnetic field generating device 40 described below in combination.

  The static magnetic field generation device (Level Magnetic Field: LMF) 40 is also called an electromagnetic brake, and reduces the discharge speed of the molten steel from the discharge hole 22 of the immersion nozzle 20 by applying a brake with a uniform static magnetic field. The static magnetic field generator 40 is installed below the electromagnetic stirrer 30. When the discharge speed of the molten steel is lowered by the static magnetic field generator 40, the flow of the molten steel does not reach the deep part of the continuous casting mold 10, and the upward flow occurs at a shallow portion of the continuous casting mold 10. As a result, the inclusion 14 existing in the continuous casting mold 10 can be levitated, and the inner part level of the slab can be improved.

  The braking effect of the static magnetic field generator 40 depends on the strength of the static magnetic field generated by the static magnetic field generator 40. The normal static magnetic field generator 40 can generate a magnetic field of about 4000 to 5000 Gauss at the maximum, but if such a magnetic field is generated, the operation of the electromagnetic stirring device 30 becomes unstable. For this reason, it is preferable that the intensity of the generated magnetic field be set to a level that does not cause any operational problems.

  Next, the relationship between the distribution of the stirring force by the electromagnetic stirrer 30 and the distribution of the magnetic field strength by the static magnetic field generator 40 will be described in detail with reference to FIG. FIG. 2 is an explanatory diagram for schematically explaining the distribution of the stirring force by the electromagnetic stirring device and the distribution of the magnetic field strength by the static magnetic field generator.

  As shown in FIG. 2, the distribution of the propulsive force by the electromagnetic stirrer 30 is a mountain-shaped distribution having a maximum value in the vicinity of the center of the electromagnetic stirrer core 32 (hereinafter also simply referred to as a core). The stirring device 30 is controlled so that there is sufficient stirring force even in the vicinity of the meniscus position 12 of the molten steel and the position of the discharge hole 22 of the immersion nozzle 20. On the other hand, as shown in FIG. 2, the distribution of the static magnetic field generated by the static magnetic field generator 40 is a mountain-shaped distribution having a maximum value at the center of the static magnetic field generator core 42 (hereinafter also simply referred to as a core). Thus, even in the vicinity of the meniscus position 12 of the molten steel and the position of the discharge hole 22 of the immersion nozzle 20, it has a large magnetic field strength.

  As shown in FIG. 2, the stirring force and the static magnetic field strength influence each other in the region from the meniscus position 12 to the discharge hole 22, and thus the stirring force of the electromagnetic stirring device 30 and the static magnetic field generation device 40. It is difficult to fully exhibit the functions of the electromagnetic stirrer 30 and the static magnetic field generator 40 only by setting the static magnetic field strength individually. Therefore, it is necessary to control each apparatus in consideration of both the influence of the stirring force by the electromagnetic stirrer 30 and the influence of the static magnetic field by the static magnetic field generator 40.

(About the static magnetic field intensity by the static magnetic field generator 40)
Next, the influence of the static magnetic field by the static magnetic field generator 40 according to the present embodiment will be described in detail with reference to FIG. FIG. 3 is a graph showing the relationship between the influence of the static magnetic field by the static magnetic field generator 40 according to the present embodiment and the slab bubble index. The horizontal axis of FIG. 3 is a value obtained by dividing the magnetic field strength Bt [Gauss] by the static magnetic field generator at the discharge hole position of the immersion nozzle by the throughput amount Q [ton / min] of the molten steel from the immersion nozzle. The vertical axis of 3 is a slab bubble index obtained by indexing the average number of bubbles remaining in the slab.

  Here, the number of bubbles remaining in the slab is an average value of the number of bubbles remaining in the slab measured by the X-ray transmission method, and the slab bubble index is obtained when the static magnetic field generator is not applied. The average value of the number of bubbles is 1, and the number of bubbles remaining in the slab is indexed. Therefore, the above slab bubble index can be considered as an index related to the inner part level of the cast slab.

  In FIG. 3, the slab width cast from 1.1 m / min to 1.5 m / min and the slab width of 1700 mm to 1900 mm is changed by changing the static magnetic field strength applied to the static magnetic field generator and the throughput amount. The slab bubble index was measured. Referring to FIG. 3, when a static magnetic field generator starts applying a static magnetic field, the slab bubble index increases for all slabs, and Bt / Q is about 250 [Gauss · min / ton]. It was found that the slab bubble index became the maximum, and after that, the slab bubble index decreased. Further, it was found that in the region where Bt / Q> 350, the slab bubble index value was stable at 0.5 or less.

  This result shows that when a static magnetic field that satisfies Bt / Q> 350 is applied by the static magnetic field generator, the number of bubbles remaining in the slab is less than half that when the static magnetic field generator is not used. ing. When Bt / Q> 350, the slab bubble index is stabilized at 0.5 or less. When Bt / Q is 350 or less, the flow of molten steel is caused by the static magnetic field applied by the static magnetic field generator. The turbulent flow prevents the bubbles from rising, whereas when Bt / Q> 350, the discharge speed of the discharge flow from the immersion nozzle is suppressed, and the bubbles are likely to rise efficiently. It is done.

  The above result is that the inner part level of the slab is improved by satisfying the relationship of Bt / Q> 350 between the static magnetic field strength of the static magnetic field generating device at the discharge hole position of the immersion nozzle and the throughput amount from the immersion nozzle. Indicates that it is possible.

(Regarding the position of the core and meniscus of the electromagnetic stirrer)
Next, the position of the core of the electromagnetic stirring device 30 and the meniscus of the molten steel will be described in detail with reference to FIG. In order to examine the relationship between the core of the electromagnetic stirrer 30 and the meniscus position of the molten steel, after applying a static magnetic field satisfying the condition of Bt / Q> 350 by the static magnetic field generator 40, the electromagnetic stirrer 30 is operated. The surface defect occurrence rate of the hot rolled pickling material was examined. Specifically, the static magnetic field generated by the static magnetic field generator 40 was constant at 4000 [Gauss], and the stirring force by the electromagnetic stirrer 30 was fixed at 700 [Pa]. Moreover, the alternating current frequency applied to the electromagnetic stirring device 30 was 4 Hz. In addition, the position (meniscus position) of the molten steel surface 12 is within the cast (for example, when performing 15 consecutive castings, such as the 7th pan or the 8th pan, in order to reduce the melting damage of the immersion nozzle 20, The position is changed at the center. Here, the surface defect occurrence rate means that when a coil is manufactured from a cast slab, surface defects such as scratches (for example, sliver-like defects caused by alumina clusters or powder inclusions) are generated. This shows the ratio of the coils that were used. That is, when a coil is produced from a slab and a surface defect occurs in b coils, the surface defect rate [%] is represented by (b / a) × 100.

  Referring to FIG. 4, when the meniscus position of the molten steel (position of the molten steel surface 12) is located outside the core range of the electromagnetic stirring device 30, the surface defect occurrence rate was 5%, whereas the meniscus is When the position is located in the range from the center of the core of the electromagnetic stirring device 30 to the upper end of the core, the surface defect occurrence rate is about 1%, which indicates that the surface quality is good. From this result, it is understood that the molten steel surface 12 in the continuous casting mold 10 needs to be located in the range from the center of the core of the electromagnetic stirring device 30 to the upper end of the core.

(Relationship between stirring force by electromagnetic stirrer and static magnetic field by static magnetic field generator)
The slab is cast by changing the stirring force of the electromagnetic stirrer 30 and the static magnetic field strength of the static magnetic field generator after satisfying the above-mentioned conditions regarding the static magnetic field strength of the static magnetic field generator and the meniscus position of the molten steel. Then, the surface defect occurrence rate of the hot rolled pickling material formed from the cast slab was examined. At this time, the alternating current frequency applied to the electromagnetic stirring device 30 was 4 Hz. FIG. 5 shows a value F / Bm [Pa / Gauss] obtained by dividing the stirring force F [Pa] by the electromagnetic stirrer 30 at the meniscus position by the magnetic field intensity Bm [Gauss] by the static magnetic field generator 40 at the meniscus position. It is the graph which showed the relationship with surface defect incidence [%].

  Here, the stirring force by said electromagnetic stirring apparatus 30 was calculated | required as follows. First, a brass plate to which a spring balance is connected in a state where there is no molten steel is placed in the continuous casting mold 10, and a current is passed through the electromagnetic stirrer 30 to measure the load of the spring balance. The measured load is divided by the product of the plate thickness and plate height of a brass plate, and then further divided by the specific gravity of the molten steel, and is obtained as a stirring force in the unit of pressure [Pa]. The reason why the brass plate is used is to match the physical properties of the molten steel.

  Referring to FIG. 5, when the stirring force F by the electromagnetic stirring device 30 is not applied, the surface defect occurrence rate is about 5%, and the surface defect occurrence rate decreases as the value of F / Bm increases. I understand. It can also be seen that in the range where the value of F / Bm exceeds 0.5, the surface defect occurrence rate is less than 1% and the stability is low. From this result, in the range where F / Bm exceeds 0.5, the vicinity of the molten steel surface 12 is sufficiently stirred by the electromagnetic stirrer 30 even though the static magnetic field is applied by the static magnetic field generator 40. It shows that the surface quality of the cast slab is improved.

  As described above, the molten steel surface 12 is positioned in the range from the center of the coil core of the electromagnetic stirrer to the upper end of the core in the continuous casting mold 10 and satisfies F / Bm> 0.5 and Bt / Q> 350. Thus, by controlling the stirring force F of the electromagnetic stirrer 30 and the static magnetic field strengths Bm and Bt by the static magnetic field generator 40, the surface quality improvement effect by the electromagnetic stirrer 30 and the improvement of the internal parts by the static magnetic field generator 40 are improved. It is possible to maximize both of the effects, and it is possible to improve both the surface quality and the internal component quality of the cast slab.

(About AC current frequency of electromagnetic stirrer)
In the electromagnetic stirrer 30 that stirs molten steel by generating an alternating magnetic field by applying an alternating current, the influence range of the stirring force varies depending on the frequency of the applied alternating current. When a high-frequency alternating current is applied to the electromagnetic stirring device 30, the penetration depth of the generated alternating magnetic field is shallow, and only the vicinity of the solidified shell in the continuous casting mold 10 is stirred while being applied. A pinch force is generated in the molten steel by the high frequency, and a force directed toward the solidified shell acts on inclusions such as bubbles. Thus, the frequency of the alternating current applied to the electromagnetic stirrer 30 affects the force acting on the stirring region of the electromagnetic stirrer 30 and inclusions such as bubbles.

  Then, the relationship between the frequency of the alternating current applied to the electromagnetic stirring apparatus 30 and the surface defect occurrence rate was examined. In the examination, the surface defect occurrence rate was measured by changing the frequency of the alternating current while satisfying the position of the meniscus and the conditions of the above (formula 1) and (formula 2). FIG. 6 is a graph showing the relationship between the frequency of the alternating current applied to the electromagnetic stirrer 30 and the surface defect occurrence rate.

  Referring to FIG. 6, the surface defect occurrence rate, which was about 5% when the electromagnetic stirring device 30 is not used, is decreased by increasing the frequency of the alternating current applied to the electromagnetic stirring device 30. It can be seen that when the applied frequency is higher than 5 Hz, the surface defect occurrence rate increases. Moreover, when the frequency of the alternating current applied to the electromagnetic stirrer 30 is in the range of 2 Hz to 10 Hz, for example, the surface defect occurrence rate is 1% or less, and good surface quality can be obtained. I understood.

  When the frequency of the applied alternating current is a low frequency of less than 2 Hz, the penetration depth of the generated magnetic field is deep, and the stirring flow on the upper surface side 16 of the mold wide surface and the stirring flow on the lower surface side 18 of the mold wide surface It is thought that the occurrence rate of surface defects deteriorates because collision and interference occur and promote the inclusion of inclusions. In addition, when the frequency of the applied alternating current exceeds 10 Hz, the influence of the above-described pinch force is increased, so that inclusions such as bubbles move to the solidified shell side and trap inclusions on the surface of the slab. Will increase.

  Thus, it has been found that the surface quality can be further improved by setting the frequency of the alternating current applied to the electromagnetic stirring device 30 to 2 Hz to 10 Hz, for example.

  Hereinafter, the continuous casting method according to the present invention will be described in detail with reference to Examples and Comparative Examples. The following embodiment is merely a specific example of the present invention, and the present invention is not limited to the embodiment described below.

  Cold-rolled plates are manufactured using slabs cast under the conditions shown in Table 1 below (Examples 1 to 8 and Comparative Examples 1 to 6). We asked for rate. The overall evaluation is also shown in Table 1. Here, the blowhole refers to a blister or bald defect in a steel sheet caused by defects such as bubbles existing inside the steel sheet after cold rolling, and the blowhole occurrence rate is from a cast slab. When a coil is manufactured, the ratio between the number of manufactured coils and the coil in which blow holes are generated is shown. In addition, the presence or absence of surface defects and blowholes was confirmed by visual observation on a coil passage line made of a cast slab. The criteria for comprehensive evaluation are as follows.

◎: Both surface defect occurrence rate and blow hole occurrence rate are 0.5% or less ○: Both surface defect occurrence rate and blow hole occurrence rate are 1.0% or less ×: Either surface defect occurrence rate or blow hole occurrence rate Is 1.0% or more

In addition, the casting_mold | template which cast the said slab is 2300 mm in long sides, 280 mm in short sides, and 950 mm in height. The electromagnetic stirrer (hereinafter also referred to as EMS) is installed such that the core height is 150 mm and the center in the height direction of the core is 200 mm from the upper end of the mold. The static magnetic field generator (hereinafter also referred to as LMF) is installed so that the core height is 200 mm and the center in the height direction of the core is 680 mm from the upper end of the mold.

  As is clear from Table 1, in Examples 1 to 8 that satisfy the conditions regarding the meniscus position of the molten steel, the condition regarding the stirring force of the electromagnetic stirrer, and the condition regarding the static magnetic field strength by the static magnetic field generator, the surface defect generation rate and blowhole generation It can be seen that both rates show good values. In particular, it can be seen that when the frequency of the alternating current applied to the electromagnetic stirrer is in the range of 2 Hz to 10 Hz, the surface defect occurrence rate is remarkably improved.

  On the other hand, in Comparative Examples 1 to 6 that do not satisfy any of the meniscus position of the molten steel, the condition relating to the stirring force of the electromagnetic stirrer, and the condition relating to the static magnetic field strength by the static magnetic field generator (namely, the * part in the table), surface defects It was found that either the generation rate or the blowhole generation rate exceeded 1%, and it was impossible to satisfy both the surface quality and the internal component quality. In addition, Comparative Example 1 is an example in which both LMF and EMS are not installed, and Comparative Examples 2 and 3 are examples in which either LMF or EMS is not installed.

  As described above, according to the method for producing a continuous cast slab according to the present invention, the surface quality and the internal parts of the slab are improved while maximizing the functions of both the electromagnetic stirrer and the static magnetic field generator. It is possible.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to this example. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

It is explanatory drawing for demonstrating the continuous casting mold which concerns on suitable embodiment of this invention. It is a top view for demonstrating the continuous casting mold which concerns on the same embodiment. It is explanatory drawing for demonstrating distribution of the stirring force by an electromagnetic stirrer, and distribution of the magnetic field intensity by a static magnetic field generator. It is the graph which showed the relationship between the magnetic field strength by a static magnetic field generator, and a slab bubble parameter | index. It is the graph which showed the relationship between the meniscus position of molten steel, and a surface defect occurrence rate. It is the graph which showed the relationship between the stirring force by an electromagnetic stirrer, and a surface defect occurrence rate. It is the graph which showed the relationship between the frequency of a magnetic stirring apparatus, and a surface defect incidence rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Continuous casting mold 12 Molten steel surface 14 Inclusion 16 Upper surface side of mold wide surface 18 Lower surface side of mold wide surface 20 Immersion nozzle 22 Discharge hole 30 Electromagnetic stirrer 32 Electromagnetic stirrer core 40 Static magnetic field generator 42 Static magnetic field generator core

Claims (2)

The molten steel is supplied to a continuous casting mold having an electromagnetic stirring device in the upper part and a static magnetic field generator in the lower part through an immersion nozzle having two downward discharge holes as a molten steel supply port, and the continuous casting. In the method for producing a continuous cast slab, the molten steel surface in the mold is controlled so as to be positioned in the range of the upper end of the core from the coil core center of the electromagnetic stirrer.
The ratio of the stirring force by the electromagnetic stirrer on the molten steel surface to the magnetic field strength by the static magnetic field generator satisfies the following (Equation 1), and the magnetic field strength by the static magnetic field generator at the position of the discharge hole is The manufacturing method of the continuous casting slab characterized by satisfy | filling the following (Formula 2).

F / Bm> 0.5 (Expression 1)
Bt / Q> 350 (Formula 2)

Here, in Formula 1, F is the stirring force [Pa] by the electromagnetic stirrer on the molten steel surface, Bm is the magnetic field strength [Gauss] by the static magnetic field generator on the molten steel surface,
In Equation 2, Bt is the magnetic field strength [Gauss] by the static magnetic field generator at the position of the submerged nozzle discharge hole, and Q is the throughput [ton / min].
  The method for producing a continuous cast slab according to claim 1, wherein the alternating current frequency of the electromagnetic stirring device is 2 Hz to 10 Hz.

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