Slab continuous casting method

Abstract

To provide a slab continuous casting method that can suppress the occurrence of a black stripe defect.SOLUTION: A continuous casting method uses a continuous casting machine (1). The continuous casting machine (1) comprises a casting mold (4) including an electromagnetic stirring core (4a). The continuous casting method comprises a supply process and an application process. In the supply process, mold powder having a content of P2O5 of 1.0% or less is supplied into the casting mold (4). In the application process, an AC magnetic filed of 0.05 T or more and 0.20 T or less is applied to molten steel (M) in the casting mold (4) by use of the electromagnetic stirring core (4a), to set a molten metal surface variation amount in meniscus to 10 mm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method for continuous casting of a strand. [Background technology]

[0002] In continuous casting, mold powder is used as a lubricant between the mold and the slab. Generally, mold powder contains P2O5. When mold powder is fed into the mold, it flows along the inner surface of the mold. The mold powder adheres to the surface of the mold. Then, the phosphorus in the mold powder diffuses to the surface of the slab. At this time, the mold powder is reduced by the aluminum in the slab. This forms a phosphorus-enriched part in the slab (hereinafter also referred to as "P-enriched part"). When a slab having a P-enriched part is hot-rolled to produce a coil, the P-enriched part may be stretched in the rolling direction, resulting in a streaky surface defect (hereinafter also referred to as "black streak defect").

[0003] The slabs produced by continuous casting require high surface quality. For example, the slabs that will be used as raw materials for ultra-low carbon steel sheets for automobiles (especially exterior materials) require extremely strict surface quality. In this case, it is necessary to minimize the occurrence of black streak defects in the coils obtained by rolling the slabs.

[0004] For example, Patent Document 1 is known as a technique for suppressing the occurrence of black streak defects. Patent Document 1 discloses a continuous casting method for ultra-low carbon steel. In the continuous casting method of Patent Document 1, a mold flux (mold powder) is used in which the P2O5 content is controlled to have a viscosity of 0.3 to 6.0 poise when melted and a solidification point of 1050 to 1250°C. Patent Document 1 describes that by setting the P2O5 content in the mold flux components to 0.5% or less, it is possible to suppress the concentration of phosphorus even if the mold flux adheres to the surface of the cast slab, and as a result, it is possible to suppress the occurrence of black streak defects. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6699345 Summary of the Invention [Problem to be solved by the invention]

[0006] As described in Patent Document 1, it is believed that the occurrence of black streak defects can be reduced by reducing the P2O5 content of the mold powder to a certain extent. However, depending on the manufacturing conditions in continuous casting, black streak defects may occur even if the P2O5 content of the mold powder is controlled.

[0007] An object of the present disclosure is to provide a method for continuous casting of a slab capable of suppressing the occurrence of black streak defects. [Means for solving the problem]

[0008] The continuous casting method according to the present disclosure uses a continuous casting machine. The continuous casting machine is equipped with a mold including an electromagnetic stirring core. The continuous casting method includes a supplying step and an application step. In the supplying step, mold powder having a P2O5 content of 1.0% or less is supplied into the mold. In the application step, an AC magnetic field of 0.05 T or more and 0.20 T or less is applied to the molten steel in the mold using the electromagnetic stirring core, and the amount of fluctuation of the molten steel surface at the meniscus is set to 10 mm or less. Effect of the Invention

[0009] According to the method for continuous casting of a slab according to the present disclosure, the occurrence of black streak defects can be suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a continuous casting machine used in a continuous casting method according to an embodiment. [Diagram 2] FIG. 2 is a flow diagram showing a method for continuously casting a slab according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] As described above, even if the content of P2O5 in the mold powder is controlled, black streak defects may occur. The present inventors have intensively studied the manufacturing conditions in continuous casting in this case and the factors that cause black streak defects. As a result, they have found that the amount of fluctuation in the molten metal level in the mold affects the occurrence of black streak defects. Specifically, the present inventors have found that by keeping the amount of fluctuation in the molten metal level in the mold small, the amount of mold powder flowing between the mold and the slab is stabilized, and therefore the formation of P-enriched parts and the occurrence of black streaks in the slab can be suppressed. This is because when the amount of mold powder flowing in becomes unstable, phosphorus is concentrated in the part of the surface of the slab where a large amount of mold powder has flowed in, and P-enriched parts are likely to be formed.

[0012] The continuous casting method according to the embodiment of the present disclosure has been completed based on the above findings.

[0013] The continuous casting method according to the embodiment uses a continuous casting machine. The continuous casting machine is equipped with a mold including an electromagnetic stirring core. The continuous casting method includes a supplying step and an application step. In the supplying step, mold powder having a P2O5 content of 1.0% or less is supplied into the mold. In the application step, an AC magnetic field of 0.05 T or more and 0.20 T or less is applied to the molten steel in the mold using the electromagnetic stirring core, and the amount of fluctuation of the molten steel surface at the meniscus is set to 10 mm or less (first configuration).

[0014] In the continuous casting method according to the first aspect, in the supply step, mold powder having a relatively low content of P2O5 is supplied into the mold. Furthermore, in the application step, the flux density of the alternating magnetic field applied by electromagnetic stirring is controlled to keep the molten metal surface fluctuation small. This stabilizes the inflow of mold powder. Furthermore, since the mold powder contains a small amount of phosphorus, P-enriched areas are unlikely to form even if the mold powder adheres to the surface of the slab. Therefore, according to the continuous casting method according to the first aspect, it is possible to reduce the occurrence of P-enriched areas, and as a result, it is possible to suppress the occurrence of black streak defects.

[0015] The continuous casting method preferably has the following configuration: the mold further includes an electromagnetic brake core, and in the applying step, a static magnetic field of 0.10 T or more and 0.40 T or less is applied to the molten steel in the mold by using the electromagnetic brake core (second configuration).

[0016] In continuous casting, high-temperature molten steel is supplied from an immersion nozzle and discharged toward the widthwise ends of the slab. When this discharged molten steel (discharge flow) collides with the inner surface (short side surface) of the mold, a flow of molten steel (reverse flow) toward the meniscus is generated. This reverse flow may cause large fluctuations in the molten metal level. Therefore, in the continuous casting method according to the second configuration, the magnetic flux density of the static magnetic field applied by the electromagnetic brake is controlled in the application step. This brakes the discharge flow from the immersion nozzle. Therefore, according to the continuous casting method of the second configuration, it is possible to more reliably keep the molten metal level fluctuations small.

[0017] Hereinafter, a continuous casting method according to an embodiment of the present disclosure will be described with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and duplicated explanations will be omitted as appropriate.

[0018] [Continuous casting machine] FIG. 1 is a schematic diagram of a continuous casting machine 1 used in the continuous casting method according to the present embodiment. The continuous casting machine 1 produces a cast piece 10. In this embodiment, the cast piece 10 is a slab. The continuous casting machine 1 includes a tundish 2, a mold 4, and a plurality of support rolls 5. In this embodiment, the continuous casting machine 1 is a vertical bending type. In short, the continuous casting machine 1 includes a vertical band, a curved portion, and a horizontal band. However, the continuous casting machine 1 may be, for example, a vertical type consisting of only a vertical band, or a curved type consisting of a curved portion and a horizontal band.

[0019] Molten steel M is supplied to the tundish 2 from a ladle (not shown). The molten steel M in the tundish 2 is supplied to the mold 4 through the submerged nozzle 3. The molten steel M in the mold 4 is cooled by the mold 4. The mold 4 includes an electromagnetic stirring core 4a and an electromagnetic brake core 4b. The electromagnetic stirring core 4a is disposed in the upper part of the mold 4, and the electromagnetic brake core 4b is disposed in the lower part of the mold 4. The electromagnetic stirring core 4a is, for example, an electromagnetic coil, and the electromagnetic brake core 4b is, for example, an electromagnet. The electromagnetic stirring core 4a is disposed near the meniscus in the vertical direction, and can apply an AC magnetic field to the molten steel M in the mold 4. The electromagnetic brake core 4b is disposed below the meniscus, and can apply a static magnetic field to the molten steel M in the mold 4. The electromagnetic stirring core 4a and the electromagnetic brake core 4b are disposed, for example, on both outer sides of the mold 4 in the thickness direction of the slab 10. The thickness direction is a direction perpendicular to the width direction and casting direction of the slab 10.

[0020] A plurality of secondary cooling nozzles (not shown) and a plurality of support rolls 5 are arranged downstream in the casting direction of the mold 4. The molten steel M is cooled in the mold 4, and then further cooled by secondary cooling water being sprayed from the secondary cooling nozzles. This forms a solidified shell S. The slab 10 in the process of solidifying here includes the solidified shell S (solid fraction 1.0) and unsolidified molten steel M (solid fraction less than 1.0). The slab 10 in the process of solidifying and including the unsolidified molten steel M is guided downstream in the casting direction by the plurality of support rolls 5. In the process, the unsolidified molten steel M gradually decreases, and a completely solidified slab 10 is formed.

[0021] [Continuous casting method] Fig. 2 is a flow diagram showing a method for continuous casting of a slab 10 according to this embodiment. As shown in Fig. 2, the method for continuous casting of steel according to this embodiment includes a supplying step (#5) and an applying step (#10). The slab 10 obtained by this continuous casting method becomes the raw material for products such as an ultra-low carbon steel sheet. Each step shown in Fig. 2 will be specifically described below.

[0022] [Supply process (#5)] In the supply step (#5), the mold powder is supplied into the mold 4. The mold powder is generally used as a lubricant between the mold 4 and the slab 10 (solidified shell S). The mold powder preferably has a chemical composition, in mass%, of SiO2: 20-45%, CaO: 30-50%, F: 2-15%, Li2O, Na2O, K2O, MgO, SrO, BaO, B2O3, Al2O3, TiO2, ZrO2, FeO, and MnO in total of 3-25%, C: 1-10%, and the remainder being P2O5 and impurities.

[0023] If the P2O5 content of the mold powder supplied into the mold 4 exceeds 1.0% by mass, the occurrence of black streak defects increases significantly. Therefore, the P2O5 content of the mold powder supplied in the supplying step (#5) is 1.0% or less. The lower the P2O5 content, the easier it is to suppress the occurrence of black streak defects. However, if the P2O5 content is low, the refining cost of the mold powder increases. From the viewpoint of reducing refining costs, the P2O5 content is preferably 0.01% or more.

[0024] Here, it is also required to suppress defects due to, for example, bubbles and inclusions in the cast slab 10 produced by continuous casting. Inclusions are generated in the molten steel M, for example, during refining of the molten steel M, i.e., before it is supplied to the tundish 2. In addition, the mold powder supplied in the supply step (#5) may become an inclusion when it is caught in the molten steel M in the mold 4. In continuous casting, Ar gas is blown into the submerged nozzle 3 to prevent the submerged nozzle 3 from being clogged by inclusions. Therefore, bubbles originating from Ar gas are present in the molten steel M supplied to the mold 4.

[0025] The bubbles and inclusions are usually removed by floating them up before the molten steel M completely solidifies, but some of the bubbles and inclusions may be captured in the solidified shell S as the molten steel M solidifies. When the bubbles and inclusions are captured in the solidified shell S, defects in the bubbles and inclusion properties occur on the surface of the slab 10. In continuous casting with a high casting speed, the average molten steel flow rate (downward flow) in the casting direction is high, making it difficult for the bubbles and inclusions to float up, and the bubbles and inclusions are easily captured in the solidified shell S. On the other hand, it is difficult to reduce the casting speed excessively because the productivity decreases when the casting speed is reduced. Therefore, in the continuous casting method according to the present embodiment, as described later, the basicity and viscosity of the mold powder supplied in the supply step (#5) are appropriately set, and a magnetic field is applied to the molten steel M by the electromagnetic stirring core 4a and the electromagnetic brake core 4b in the application step (#10). This makes it possible to suppress defects in the bubbles and inclusion properties even when the casting speed is relatively high.

[0026] The basicity (CaO / SiO2) and viscosity of the mold powder supplied into the mold 4 in the supply step (#5) are preferably set appropriately so that defects due to inclusions are unlikely to occur. If the basicity of the mold powder is less than 1.0, the interfacial tension with the molten steel M decreases, and the mold powder is likely to be wetted by the molten steel M. Therefore, the mold powder is likely to be caught in the molten steel M. If the basicity of the mold powder is greater than 1.6, the solidification point becomes too high, and the function as a lubricant between the mold 4 and the slab 10 decreases. In this case, the friction force between the mold 4 and the slab 10 increases, which may lead to operational troubles such as breakouts in which the molten steel M leaks. Therefore, the basicity of the mold powder is preferably 1.0 or more and 1.6 or less.

[0027] If the viscosity of the mold powder is less than 0.3 poise, the mold powder is likely to be caught in the molten steel M, and surface defects of inclusion properties are likely to occur. If the viscosity of the mold powder is more than 6.0 poise, the function of the mold powder as a lubricant between the mold 4 and the cast piece 10 is reduced. Therefore, the viscosity of the mold powder is preferably 0.3 poise or more and 6.0 poise or less. The above-mentioned viscosity means the viscosity of the mold powder in a molten state at 1300°C.

[0028] [Marking process (#10)] In the application step (#10), an AC magnetic field is applied to the molten steel M in the mold 4 using the electromagnetic stirring core 4a. By stirring the molten steel M with the AC magnetic field, the amount of bubbles and inclusions that are captured in the solidified shell S can be reduced.

[0029] If the magnetic flux density of the AC magnetic field applied by the electromagnetic stirring core 4a is less than 0.05T, the molten steel M cannot be sufficiently stirred, and the capture of bubbles and inclusions by the solidified shell S is difficult to suppress. Here, "T" means the unit of magnetic flux density (tesla). Also, if the magnetic flux density of the AC magnetic field is more than 0.20T, the amount of fluctuation of the molten steel surface becomes too large, so that the inflow amount of mold powder becomes unstable and the surface quality of the cast slab 10 deteriorates. Therefore, the magnetic flux density of the AC magnetic field applied by the electromagnetic stirring core 4a in the application step (#10) is 0.05T or more and 0.20T or less.

[0030] In this embodiment, the casting speed is not particularly limited. The casting speed is, for example, 1.1 to 2.0 m / min. However, when the casting speed is higher than about 1.3 m / min, a reverse flow is likely to be generated when the discharge flow discharged from the discharge hole of the submerged nozzle 3 collides with the inner surface of the mold 4. As described above, when a reverse flow is generated, the amount of fluctuation of the molten steel level may increase. Therefore, when continuous casting is performed under manufacturing conditions with a high casting speed, it is preferable to apply a static magnetic field to the molten steel M using the electromagnetic brake core 4b in order to brake the discharge flow.

[0031] In the application step (#10), a static magnetic field is further applied to the molten steel M in the mold 4 using the electromagnetic brake core 4b. In this case, the discharge flow receives a braking force in the direction opposite to the flow direction due to the action of the static magnetic field. Therefore, the discharge flow discharged from the discharge hole toward the width direction end of the solidified shell S is weakened. In addition, the electromagnetic brake core 4b can promote the floating of inclusions in the molten steel M, and also plays a role in separating the inclusions from the molten steel M.

[0032] If the magnetic flux density of the static magnetic field applied by the electromagnetic brake core 4b is less than 0.10 T, the discharge flow cannot be sufficiently braked, and the amount of fluctuation in the molten metal level may become large. If the magnetic flux density of the static magnetic field is more than 0.40 T, the cost of investing in equipment for applying the magnetic field increases. Therefore, the magnetic flux density of the static magnetic field applied by the electromagnetic brake core 4b is preferably 0.10 T or more and 0.40 T or less. In this case, the amount of fluctuation in the molten metal level can be more reliably kept small.

[0033] Here, the magnetic flux density of the electromagnetic stirrer core 4a and the electromagnetic brake core 4b was determined based on the application conditions (current and frequency) and the results of measuring the magnetic flux density at the center of each core when the electromagnetic stirrer core 4a and the electromagnetic brake core 4b were operated in a mold 4 in a cold state without the presence of molten steel M. Note that since the magnetic field applied by the electromagnetic stirrer core 4a is an AC magnetic field, the maximum value of the time change in the magnetic flux density was taken as the magnetic flux density value for the electromagnetic stirrer core 4a.

[0034] In the application step (#10), the magnetic flux density of the alternating magnetic field generated by the electromagnetic stirring core 4a is set to 0.20 T or less, and a static magnetic field of 0.10 T or more is applied to the molten steel M by the electromagnetic brake core 4b to brake the discharge flow from the submerged entry nozzle 3, thereby keeping the amount of fluctuation of the molten steel surface at the meniscus small.

[0035] If the amount of fluctuation of the mold level is more than 10 mm, the amount of mold powder flowing in becomes unstable. In this case, phosphorus is concentrated more on the surface of the slab 10 in the area between the mold 4 and the slab 10 where a large amount of mold powder has flowed in, and as a result, black streaks are more likely to occur. Furthermore, if the amount of fluctuation of the mold level is more than 10 mm, the molten mold powder itself is more likely to be caught in the molten steel M, and defects in the inclusion properties also occur. Therefore, the amount of fluctuation of the mold level is set to 10 mm or less.

[0036] The amount of molten metal level fluctuation can be grasped, for example, by measuring according to the following procedure. Using a non-contact eddy current displacement meter or the like, the height of the molten metal level from the top of the mold 4 toward the meniscus is measured for 10 seconds. The difference between the maximum height and the minimum height of the molten metal level during the 10 seconds during which the measurement is taken is regarded as the amount of molten metal level fluctuation. However, the position at which the molten metal level is measured is not particularly limited, and the measurement may be performed at any position on the mold 4. The measurement of the molten metal level height may be performed at one location or multiple locations.

[0037] [effect] In the continuous casting method according to this embodiment, in the supply step (#5), mold powder having a relatively low content of P2O5 is supplied into the mold 4. Furthermore, in the application step (#10), the flux density of the alternating magnetic field applied by electromagnetic stirring is controlled to keep the molten metal surface fluctuation small. This stabilizes the inflow of mold powder. Furthermore, since the mold powder contains little phosphorus, P-enriched areas are unlikely to form even if the mold powder adheres to the surface of the slab 10. Therefore, according to the continuous casting method according to this embodiment, it is possible to reduce the occurrence of P-enriched areas, and as a result, it is possible to suppress the occurrence of black streak defects.

[0038] In the application step (#10), an AC magnetic field is applied to the molten steel M in the mold 4 by the electromagnetic stirrer core 4a, thereby stirring the molten steel M. This makes it possible to reduce the amount of bubbles and inclusions that are captured in the solidified shell S. Furthermore, in the application step (#10), a static magnetic field is applied to the molten steel M by the electromagnetic brake core 4b, thereby floating the inclusions in the molten steel M and separating them from the molten steel M. Therefore, according to the continuous casting method of this embodiment, the occurrence of defects in the physical properties of bubbles and inclusions can also be suppressed. EXAMPLES

[0039] In order to confirm the effects of the continuous casting method according to the embodiment, the following tests were carried out and the results were evaluated. In this example, continuous casting was carried out under various conditions to produce extra-low carbon steel slabs. Each slab was then hot-rolled, cold-rolled, annealed, and galvanized to produce coils, and the resulting coils were subjected to a surface inspection. In the coil surface inspection, defects due to bubbles and inclusions were distinguished from black streak defects and the number of each type of defect was counted.

[0040] In this test, a cast slab was produced using a vertical bending type continuous casting machine shown in Figure 1. The mold was a copper water-cooled type with a length of 900 mm. The mold had a rectangular cross section. The cast slab had a thickness of 250 mm and a width of 1250 mm. The specific water flow rate of the cooling water sprayed from the secondary cooling nozzle was 1.5 to 2.5 L / kg-steel. The amount of Ar gas sprayed into the submerged nozzle was 7 NL / min.

[0041] The main chemical compositions of the molten steel used in the continuous casting were C: 0.0015-0.0020%, Si: 0.015-0.020%, Mn: 0.5-0.6%, P: 0.020-0.025%, S: 0.007-0.009%, N: 0.0020-0.0035%, Ti: 0.005-0.010%, and Nb: 0.005-0.010%.

[0042] The test conditions and defect evaluation results of this embodiment are shown in Table 1. In Table 1, the test conditions include the thickness of the slab produced by continuous casting, the casting speed, the magnetic flux density of the electromagnetic stirring, the magnetic flux density of the electromagnetic brake, the mold powder properties (P2O5 content, basicity, and viscosity), and the molten steel level fluctuation amount. The magnetic flux density is the magnetic flux density of the magnetic field applied to the molten steel in the mold by the electromagnetic stirring or electromagnetic brake. In Table 1, a slab produced under test conditions that satisfy all of the following conditions 1 to 3 is represented as an invention example, and a slab produced under test conditions that do not satisfy at least one of conditions 1 to 3 is represented as a comparative example. In Comparative Examples 1 to 6 shown in Table 1, the test conditions that do not satisfy each condition are marked with a "*". Condition 1: The magnetic flux density of the electromagnetic stirring is 0.05T or more and 0.20T or less. Condition 2: The P2O5 content of the mold powder is 1.0% or less. Condition 3: The amount of fluctuation of the molten metal level is 10 mm or less.

[0043] [Table 1]

[0044] In the defect evaluation results in Table 1, for air bubble / inclusion defects and black streak defects, a rating of "excellent," "good," or "unacceptable" was given depending on the number of defects that occurred in one coil. Specific judgment criteria are shown below. For the overall evaluation, if the air bubble / inclusion defects were "excellent" or "good," and the black streak defects were "excellent" or "good," the coil was deemed to have passed. Conversely, if at least one of the air bubble / inclusion defects and the black streak defects was "unacceptable," the coil would need to be machined or ground, which would reduce the yield, and so the overall evaluation was deemed to have failed. Excellent: 2 or fewer defects Good: 4 or fewer defects Unacceptable: 5 or more defects

[0045] As shown in Table 1, all of Examples 1 to 7 of the present invention satisfied all of the conditions 1 to 3. Therefore, Examples 1 to 7 of the present invention obtained cast pieces with good evaluations of defects of voids / inclusions and black streak defects. In other words, the overall evaluation was pass, and the occurrence of defects was suppressed.

[0046] In particular, in Example 2 of the invention, the P2O5 content of the mold powder is 1.00%, which does not satisfy the range of the P2O5 content of the mold powder (0.5% or less) specified in Patent Document 1. However, in Example 2 of the invention, by applying an AC magnetic field by electromagnetic stirring, the entrainment of inclusions such as mold powder was reduced, and both defects of bubbles / inclusions and black streak defects could be reduced.

[0047] In Examples 6 and 7, a static magnetic field generated by an electromagnetic brake was applied to the molten steel in addition to an AC magnetic field generated by electromagnetic stirring. Example 6 had a smaller amount of molten steel level fluctuation and fewer defects in terms of bubbles and inclusions compared to Example 3, which had the same test conditions except for the magnetic flux density of the electromagnetic brake. Also, Example 7 had a smaller amount of molten steel level fluctuation than Example 3, despite having a faster casting speed. This shows that by using an electromagnetic brake, it is possible to more reliably keep the amount of molten steel level fluctuation small and suppress the occurrence of defects.

[0048] In Comparative Examples 1 and 2, the content of P2O5 in the mold powder did not satisfy Condition 2. In these cases, the evaluation of the black streak defect was "fail," and the overall evaluation was unsuccessful.

[0049] In Comparative Examples 3 and 4, the magnetic flux density of the electromagnetic stirring was smaller than the range of Condition 1. In these cases, the evaluation of the bubble / inclusion defect was "fail", and the overall evaluation was fail. In Comparative Example 5, the magnetic flux density of the electromagnetic stirring was larger than the range of Condition 1. Furthermore, the amount of fluctuation in the molten metal surface increased, and Condition 3 was not met. As a result, the evaluation of the black streak defect was "fail", and the overall evaluation was fail.

[0050] In Comparative Example 6, the P2O5 content of the mold powder and the magnetic flux density of the electromagnetic stirring satisfied conditions 1 and 2, but the amount of fluctuation in the molten metal surface did not satisfy condition 3. In this case, the evaluations of both the bubble / inclusion defects and the black streak defects were "fail," so the overall evaluation was unsuccessful.

[0051] The embodiments of the present disclosure have been described above. However, the above-described embodiments are merely examples for implementing the present disclosure. Therefore, the present disclosure is not limited to the above-described embodiments, and can be implemented by appropriately modifying the above-described embodiments without departing from the spirit of the present disclosure. [Explanation of symbols]

[0052] 1: Continuous casting machine 4: Mold 4a: Electromagnetic stirring core 4b: Electromagnetic brake core 10: Casting M: Molten steel

Claims

1. A method for continuously casting a slab using a continuous casting machine equipped with a mold including an electromagnetic stirring core, P ２ O ５ A supplying step of supplying a molding powder having a content of 1.0% or less into the mold; and an application step of applying an AC magnetic field of 0.05 T or more and 0.20 T or less to the molten steel in the mold using the electromagnetic stirring core, thereby making a molten steel surface fluctuation amount at the meniscus 10 mm or less.

2. The continuous casting method according to claim 1, The mold further includes an electromagnetic brake core; The continuous casting method further comprises applying a static magnetic field of 0.10 T or more and 0.40 T or less to the molten steel in the mold using the electromagnetic brake core in the application step.

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