Mold and continuous casting method for steel

Abstract

To provide a casting mold capable of enhancing wettability with a molten mold flux.SOLUTION: A casting mold according to the invention is composed of a plurality of mold copper plates and is used for continuous casting of steel. Therein: a molten steel contact surface of the casting mold is coated with a coating including one of, or two or more of metal carbide, metal nitride and metal carbonitride; and there is disposed, under the coating, a heterogeneous material-filled part filled with a metal or a non-metal having a thermal conductivity different from that of the mold copper plate.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a mold used for continuous casting of steel and a method for continuous casting of steel using the mold.

Background Art

[0002] In continuous casting, increasing the casting speed is essential for improving productivity. However, there are problems such as the sticking of the solidified shell due to insufficient consumption of mold flux and non-uniform solidification due to non-uniform inflow of mold flux. When non-uniform inflow of mold flux occurs, an air gap layer with low thermal conductivity is formed between the mold flux and the mold, and the heat extraction from the molten steel becomes partially small. As a result, regions with a large and small amount of heat extraction from the molten steel occur, and a problem of non-uniform solidification where the thickness of the solidified shell becomes non-uniform occurs. When the problem of non-uniform solidification occurs, surface defects such as longitudinal cracks occur in the slab produced by continuous casting. Furthermore, in medium carbon steel grades such as hypoeutectoid steel, in addition to the above problems during high-speed casting, the volume change due to δ / γ transformation during solidification becomes large, so the problem of non-uniform solidification tends to become even larger.

[0003] Regarding such problems, Patent Document 1 discloses a mold for continuous casting in which an amorphous alloy coating made of an iron alloy or a nickel alloy is applied to the molten steel contact surface of the mold. According to Patent Document 1, by applying the coating, the mold can be provided with high wear resistance, and thereby, smooth continuous casting of steel and extension of the mold life can be achieved.

[0004] Also, Patent Document 2 discloses a mold in which a dissimilar conduction metal filling part filled with a metal having a different thermal conductivity from the mold is regularly provided on the molten steel contact surface of the mold. According to Patent Document 2, by providing the dissimilar conduction metal filling part and periodically increasing and decreasing the thermal resistance of the mold, the stress due to the phase transformation of the solidified shell is reduced, the deformation of the solidified shell is reduced, and thereby, non-uniform solidification of the solidified shell can be suppressed.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2001-105103 [Patent Document 2] Japanese Patent Publication No. 2017-24079 [Overview of the project] [Problems that the invention aims to solve]

[0006] In the mold for continuous casting disclosed in Patent Document 1, the surface facing the casting space is coated with a molten layer of amorphous alloy, but this coating has low wettability with the molten mold flux. As a result, when the molten mold flux has difficulty flowing between the molten steel and the mold under high-speed casting conditions, stalemate occurs between the mold and the solidified shell. Furthermore, even under normal casting conditions, the low wettability between the coating and the molten mold flux causes the molten mold flux to flow unevenly, forming an air gap layer and resulting in uneven solidification of the molten steel.

[0007] Furthermore, the mold disclosed in Patent Document 2, which has regularly spaced dissimilar conductive metal filling sections, has the problem of low wettability with the molten mold flux, leading to problems such as sticking between the mold and the solidified shell, and uneven solidification of the molten steel due to the formation of an air gap layer. In addition, when an air gap layer is formed, the effect of providing dissimilar conductive metal filling sections to reduce deformation of the solidified shell is diminished.

[0008] Furthermore, the formation of an air gap layer reduces the amount of heat removed from the mold, which presents the challenge of making it difficult to improve the casting speed and thus the mold's production capacity. The present invention has been made in view of the above problems, and its purpose is to provide a mold that can improve wettability with molten mold flux and suppress the formation of an air gap layer, and a continuous casting method for steel using said mold. [Means for solving the problem]

[0009] The means to solve the above problems are as follows: [1] A mold for continuous casting of steel, comprising a plurality of mold copper plates, wherein the molten steel contact surface of the mold is covered with a coating containing one or more of metal carbides, metal nitrides, and metal carbonitrides, and a dissimilar material filling section is provided below the coating, which is filled with a metal or nonmetal having a different thermal conductivity than the mold copper plates. [2] The mold according to [1], wherein the coating comprises 20% by mass or more of a metal or alloy consisting of two or more of Ni, Cr, Co and Fe. [3] The mold according to [1] or [2], wherein the thickness of the coating is 50 μm or more and 10 mm or less. A method for continuous casting steel, comprising continuously casting steel using a mold described in any of [4][1] to [3]. [Effects of the Invention]

[0010] The mold according to the present invention has higher wettability with molten mold flux at high temperatures than conventional molds, and the contact angle with the molten mold flux is smaller, so uneven flow of molten mold flux can be suppressed. As a result, the formation of an air gap layer between the molten mold flux and the mold is suppressed, and uneven solidification of molten steel can be suppressed. In addition, since the molten mold flux, which acts as a lubricant in the mold, flows more easily between the molten steel and the mold, sticking between the solidified shell and the mold is suppressed, enabling stable operation of high-speed continuous casting of steel. Furthermore, by suppressing the formation of an air gap layer, the amount of heat removed from the mold is increased, so the casting speed can be improved and the production capacity of the mold can be increased. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a continuous casting apparatus having a mold according to this embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view showing a part of the mold. [Figure 3] Figure 3 is an enlarged view of section A in Figure 2. [Figure 4] Figure 4 is a graph showing the relationship between the TiC content of each metal and the contact angle with the molten mold flux. [Modes for carrying out the invention]

[0012] The present invention will be described below through embodiments of the present invention. The following embodiments are preferred examples of the present invention and are not limiting in any way.

[0013] Figure 1 is a schematic cross-sectional view showing an example of a continuous casting apparatus 10 having a mold 12 according to this embodiment. The continuous casting apparatus 10 includes a mold 12, a tundish 14 installed above the mold 12, and a plurality of slab support rolls 16 arranged in a row below the mold 12. Although not shown in the figure, a ladle for holding molten steel 18 is installed above the tundish 14, and the molten steel 18 is poured into the tundish 14 from the bottom of the ladle. An immersion nozzle 20 is installed at the bottom of the tundish 14, and the molten steel 18 is poured into the mold 12 through the immersion nozzle 20. The molten steel 18 is cooled and solidified from the inner surface of the mold 12, forming a solidified shell 24. As a result, a slab 28 is formed with the solidified shell 24 as its outer shell and an unsolidified layer 26 made of molten steel 18 inside.

[0014] Multiple secondary cooling zones 30, each equipped with a spray nozzle (not shown), are installed in the gaps between adjacent slab support rolls 16 in the casting direction, extending from directly below the mold 12 along the casting direction. The slab 28 is cooled as it is pulled out by the cooling water sprayed from the spray nozzles of the secondary cooling zones 30. As the slab 28 is conveyed by the slab support rolls 16 and passes through the multiple secondary cooling zones 30, the solidified shell 24 is properly cooled, the solidification of the unsolidified layer 26 progresses, and the solidification of the slab 28 is completed.

[0015] Downstream in the casting direction, a plurality of conveying rolls 17 for continuously conveying the slab 28 are installed. Above the conveying rolls 17, a slab cutting machine 32 for cutting the slab 28 is arranged. After the completion of solidification, the slab 28 is cut into slabs 28a of a predetermined length by the slab cutting machine 32. In this way, the slab 28a made of steel is continuously cast using the continuous casting facility 10.

[0016] Figure 2 is a schematic cross-sectional view showing a part of the mold 12. The mold 12 is composed of four mold copper plates 13 combined so as to be substantially square tube-shaped according to the shape of the slab to be cast. The inner surfaces (the surfaces on the side in contact with the molten steel 18) of the four mold copper plates 13 are covered by a coating 22. Also, below the coating 22 and on the inner surface of the mold copper plate, a dissimilar material filling portion 23 filled with a metal or non-metal having a different thermal conductivity from the mold copper plate is provided. The dissimilar material filling portion 23 is formed, for example, by filling a metal or non-metal inside a circular concave groove independently processed on the inner surface of the mold copper plate 13. The filling thickness of the dissimilar material filling portion 23 is preferably 50 μm or more. The filling means may be filling by applying plating treatment or spraying treatment, or may be filling by fitting a metal and non-metal conforming to the shape of the circular concave groove into the circular concave groove.

[0017] Also, the upper surface of the molten steel 18 in the mold 12 is covered with molten mold flux 19 (hereinafter referred to as molten mold flux 19). The molten mold flux 19 flows in between the mold 12 and the molten steel 18 and serves as a lubricant. By the inflow of the molten mold flux serving as a lubricant between the mold 12 and the molten steel 18, the sticking between the mold 12 and the solidification shell 24 is suppressed. In a state covered with the molten mold flux 19, the molten steel 18 is injected into the mold 12 through the immersion nozzle 20. The molten steel 18 injected into the mold 12 is cooled by the mold 12. As a result, the molten steel 18 at the interface between the mold 12 and the molten steel 18 solidifies, and the solidification shell 24 is formed.

[0018] In the cooling of molten steel 18 by such a mold 12, if the molten mold flux 19 flows unevenly between the mold 12 and the molten steel 18, an air gap layer with low thermal conductivity is formed in the region where the molten mold flux 19 does not flow, and the amount of heat extraction from the molten steel 18 decreases. When there is a region where the amount of heat extraction is partially reduced, the solidification of the molten steel 18 in contact with the region is delayed, and the problem of non-uniform solidification occurs. Furthermore, since the molten mold flux 19 serves as a lubricant, there is a risk of sticking between the mold 12 and the solidification shell 24 in the region where the molten mold flux 19 does not flow and the air gap layer is not formed.

[0019] In contrast, in the mold 12 according to the present embodiment, the inner surface of the mold copper plate 13 in contact with the molten steel 18 is coated with a coating 22 containing one or more of metal carbides, metal nitrides, and metal carbonitrides. As a result, the wettability between the inner surface of the mold copper plate 13 and the molten mold flux 19 at high temperatures is improved, and the uneven inflow of the molten mold flux 19 is suppressed. As a result, the generation of an air gap due to the uneven inflow of the molten mold flux 19 at the initial stage of solidification of the molten steel 18, and the non-uniform growth and longitudinal cracking of the slab due to the non-uniformity of the thermal resistance between the mold and the molten steel can be suppressed. Furthermore, the risk of sticking between the mold 12 and the solidification shell 24 can also be reduced.

[0020] FIG. 3 is an enlarged view of part A in FIG. 2. As shown in FIG. 3, a heterogeneous material filling portion 23 filled with a metal or non-metal having a thermal conductivity different from that of the mold copper plate is provided under the coating 22. By providing the heterogeneous material filling portion 23, the thermal resistance of the mold can be periodically increased and decreased, and the stress due to the phase change of the solidification shell can be reduced. As a result, the deformation of the solidification shell is reduced, the non-uniform solidification of the solidification shell is suppressed, and the stress is dispersed and the amount of individual strain is reduced. As a result, the occurrence of surface cracks on the surface of the solidification shell can be suppressed.

[0021] In a mold 12 provided with a dissimilar material filling section 23, if the coating 22 is not provided, the molten mold flux 19 will flow unevenly between the mold 12 and the molten steel 18, reducing the above effect and making it impossible to suppress the occurrence of surface cracks on the solidified shell surface. On the other hand, by providing the coating 22, the uneven flow of the molten mold flux 19 is suppressed at high temperatures, and the above effect of providing the dissimilar material filling section 23 makes it possible to suppress the occurrence of surface cracks on the solidified shell surface.

[0022] The coating 22 is provided to suppress the uneven inflow of molten mold flux 19 into the dissimilar material filling section 23. For this reason, it is not necessary for the entire inner surface of the mold copper plate 13 to be covered with the coating 22; it is sufficient for at least the area up to where the dissimilar material filling section 23 is provided to be covered with the coating 22.

[0023] As the metal carbides, metal nitrides, and metal carbonitrides contained in coating 22, for example, one or more of TiC, SiC, ZrC, TiN, CrN, TiAlN, and TiCN can be used. Among these, it is preferable to use TiC, which is a metal carbide. Furthermore, it is preferable that the content of metal carbides, metal nitrides, and metal carbonitrides contained in coating 22 be 0.1% by mass or more and 80.0% by mass or less. If the content of metal carbides, metal nitrides, and metal carbonitrides contained in coating 22 is greater than 80.0% by mass, it is undesirable because it may cause cracks in the coating layer of coating 22. Also, if the content of metal carbides, metal nitrides, and metal carbonitrides contained in coating 22 is less than 0.1% by mass, it is undesirable because it reduces the effect of improving wettability with the molten mold flux 19.

[0024] Furthermore, it is preferable that the coating 22 contains 20% by mass or more of a metal or alloy composed of two or more of Ni, Cr, Co, and Fe. If the amount of a metal or alloy composed of two or more of Ni, Cr, Co, and Fe in the coating 22 is less than 20% by mass, it becomes difficult to form the coating 22, which is undesirable. Since the coating 22 contains at least 0.1% by mass of metal carbides, metal nitrides, and metal carbonitrides, the upper limit for the amount of a metal or alloy composed of two or more of Ni, Cr, Co, and Fe in the coating 22 is 99.9% by mass.

[0025] Furthermore, the coating 22 may contain impurities that are inevitably mixed in, in amounts of 5% by mass or less. If the amount is 5% by mass or less, the presence of such impurities will not affect the wettability with the molten mold flux 19.

[0026] The thickness of the coating 22 is preferably 50 μm or more and 10 mm or less. By setting the thickness of the coating 22 to 50 μm or more and 10 mm or less, the loss of the coating 22 due to wear can be suppressed, and the reduction in the amount of heat removed from the mold 12 can be suppressed, ensuring a solidified shell thickness that allows for continuous casting. On the other hand, if the thickness of the coating 22 is less than 50 μm, there is a risk that part of the coating 22 will be lost due to wear, which is undesirable. Also, if the thickness of the coating 22 is thicker than 10 mm, the amount of heat removed from the mold 12 will decrease, the solidified shell thickness will become thinner, and casting of the slab will become difficult, which is undesirable. Furthermore, the thickness of the coating 22 is more preferably 0.1 mm or more and 0.3 mm or less. By setting the thickness of the coating 22 to 0.1 mm or more and 0.3 mm or less, the loss of the coating 22 due to wear and the reduction in the amount of heat removed from the mold 12 can be further suppressed. In addition, the thickness of the dissimilar material filling section 23 is preferably 10 mm or less when combined with the thickness of the coating 22. This suppresses the reduction in heat dissipation from the mold 12, ensuring a solidified shell thickness that allows for continuous casting.

[0027] The method for covering the mold copper plate 13 with the coating 22 is not particularly limited, but for example, the contact surface of the mold copper plate 13 that comes into contact with the molten steel 18 may be covered with the coating 22 using laser overlay welding.

[0028] Next, we will explain the experimental results that confirmed that coating the mold copper plate 13 with coating 22 improves wettability with the molten mold flux 19 at high temperatures. In Invention Example 1, a metal piece with an area of ​​10 mm x 10 mm was laser-clad welded with a powder material prepared by mixing TiC powder in a ratio of 20% by mass and Inconel powder in a ratio of 80% by mass, and a test piece was prepared covered with a coating with a thickness of 0.2 mm.

[0029] In Invention Example 2, a test specimen was prepared by laser cladding welding a powder material, which consisted of a mixture of 50% by mass TiC powder and 50% by mass Ni powder, onto a metal piece of the same size, and then coated with a coating 0.2 mm thick. In Invention Example 3, a test specimen was prepared by laser cladding welding a powder material, which consisted of a mixture of 50% by mass TiC powder and 50% by mass Co powder, onto a metal piece of the same size, and then coated with a coating 0.2 mm thick. In Invention Example 4, a test specimen was prepared by laser cladding welding a powder material, which consisted of a mixture of 50% by mass TiC powder and 50% by mass Fe powder, onto a metal piece of the same size, and then coated with a coating 0.2 mm thick.

[0030] In Invention Example 5, a test specimen was prepared by thermal spraying a powder material, which was a mixture of 0.1% by mass of TiC powder and 99.9% by mass of Ni powder, onto a metal piece of the same size, resulting in a coating with a thickness of 0.2 mm. In Invention Example 6, a test specimen was prepared by thermal spraying TiC powder onto a metal piece of the same size, resulting in a coating with a thickness of 0.2 mm. In Invention Example 7, a test specimen was prepared by thermal spraying TiN powder onto a metal piece of the same size, resulting in a coating with a thickness of 0.2 mm. On the other hand, in Conventional Example 1, a test specimen was prepared by thermal spraying a Ni-Co (Ni:Co=50:50) plated coating with a thickness of 0.2 mm onto a metal piece of the same size.

[0031] A 2 mm square mold flux was placed on the test specimens of Invention Examples 1-6 and Conventional Example 1, and the temperature was raised from room temperature in a point-focused infrared imaging furnace. The mold flux used in the experiment mainly consisted of SiO2: 30% by mass, Al2O3: 5% by mass, and CaO: 30% by mass, and also contained MgO, Na2O, and LiO2. The basicity of the mold flux (CaO / SiO2) was 1. While videotaping the furnace, the temperature of the mold flux was raised to 1000°C, melted into droplets, and then the contact angle between the droplet-shaped molten mold flux and the test specimen was measured. The results of the contact angle measurement are shown in Table 1 below.

[0032] [Table 1]

[0033] As shown in Table 1, the contact angle between the conventional Ni-Co plating coating and the molten mold flux was 59°. In contrast, the contact angles between the coatings in Experimental Examples 1-7, which contained metal carbides or metal nitrides, and the molten mold flux were all smaller than those of the conventional example. From these results, it was confirmed that coating the contact surface of the mold copper plate 13 with the molten steel 18 with a coating containing metal carbides or metal nitrides can improve the wettability with the molten mold flux at high temperatures compared to conventional methods. This improvement in wettability with the molten mold flux is presumed to be due to the improved reactivity between the molten mold flux and the coating material caused by the metal carbides or metal nitrides distributed on the mold surface, which reduces the surface tension between the molten mold flux and the mold. Since a similar effect can be expected with metal carbonitrides, it is thought that coating the contact surface of the mold copper plate 13 with the molten steel 18 with a coating containing metal carbonitrides can improve the wettability with the molten flux compared to conventional methods. Furthermore, since the reactivity between the molten mold flux and the coating material is improved regardless of the composition of the mold flux, the above effects can be obtained similarly regardless of the composition of the mold flux.

[0034] Next, the influence of the metal carbide and metal content in coating 22 will be explained. Test specimens were prepared by coating them with a 0.2 mm thick coating using a powder material prepared by mixing TiC powder with Ni powder, Fe powder, Co powder, or Inconel powder in predetermined ratios. Mold flux was placed on these test specimens, and the temperature was raised from room temperature in a focusing infrared imaging furnace to melt the mold flux into droplets. The contact angle between the droplet-shaped molten mold flux and the test specimen was then measured. The results of the contact angle measurement are shown in Table 2 below. The mold flux used mainly consists of SiO2: 30% by mass, Al2O3: 5% by mass, and CaO: 30% by mass, and also contains MgO, Na2O, and LiO2. The basicity of the mold flux (CaO / SiO2) is 1.

[0035] [Table 2]

[0036] Figure 4 is a graph showing the relationship between the TiC content of each metal and the contact angle with the molten mold flux, and is a graph of Table 2. In Figure 4, the horizontal axis is the TiC content (mass%), and the vertical axis is the contact angle with the mold flux (°). As shown in Figure 4, among Ni, Fe, Co, and Inconel, coatings using Ni or Inconel had a smaller contact angle with the molten mold flux at high temperatures than coatings using Fe or Co. From this result, it can be seen that among Ni, Fe, Co, and Inconel, it is preferable to use Ni or Inconel as the metal to be mixed with TiC.

[0037] Furthermore, when using Ni or Inconel, it is preferable to have a TiC content of 10% by mass or more and 80% by mass or less. This allows the contact angle with the molten mold flux at high temperatures to be 30° or less. When using Ni or Inconel, it is even more preferable to have a TiC content of 20% by mass or more and 60% by mass or less. This allows the contact angle with the molten mold flux at high temperatures to be reduced to 20° or less.

[0038] Furthermore, when using Ni or Inconel, it can be seen that the contact angle with the molten mold flux at high temperatures can be further reduced by setting the TiC content to 20% by mass or more and 40% by mass or less. From these results, it can be seen that when using Ni or Inconel as the metal mixed with TiC, it is even more preferable to set the TiC content to 20% by mass or more and 40% by mass or less.

[0039] As described above, the mold 12 according to this embodiment has high wettability with the molten mold flux 19 and a small contact angle with the molten mold flux 19. As a result, the molten mold flux 19 can flow uniformly between the molten steel 18 and the mold 12, thereby suppressing the uneven flow of the molten mold flux 19. Consequently, the formation of an air gap layer between the molten mold flux 19 and the mold is suppressed, and uneven solidification of the molten steel can be suppressed. Furthermore, since sticking between the solidified shell and the mold is suppressed and the amount of heat removed from the mold increases, stable operation of high-speed continuous casting can be achieved by performing continuous casting of steel using this mold. Moreover, by using the mold 12 according to this embodiment, the effect of suppressing the occurrence of surface cracks on the solidified shell surface due to the provision of a dissimilar material filling section 23 can also be obtained.

[0040] In this embodiment, an example is shown in which all inner surfaces of the four mold copper plates 13 constituting the mold 12 are covered with coating 22, and a dissimilar material filling section 23 is provided beneath the coating 22, but the invention is not limited to this. It is sufficient that at least one of the four mold copper plates constituting the mold has its inner surface covered with coating 22 and a dissimilar material filling section 23 is provided. By using a mold composed of such mold copper plates, it is possible to suppress uneven solidification of molten steel and suppress smearing between the solidified shell and the mold compared to using a mold in which all inner surfaces of the four mold copper plates are covered with coating 22 and a dissimilar material filling section 23 is not provided. [Examples]

[0041] Test casting of medium carbon steel (chemical composition: C: 0.08~0.17 mass%, Si: 0.10~0.30 mass%, Mn: 0.50~1.20 mass%, P: 0.010~0.030 mass%, S: 0.005~0.015 mass%, Al: 0.020~0.040 mass%) was carried out under conditions of a casting speed of 2.3 m / min, using the same mold flux as used in the experiment to confirm the contact angle. A circular recess with a diameter of 5 mm was made on the surface of the mold for continuous casting, and a dissimilar material filling section was provided in this recess, filled with Ni to a maximum thickness of 1 mm. This was then coated with TiC20 mass%-Inconel80 mass% (Inventive Example 11), TiC50 mass%-Ni50 mass% (Inventive Example 12), TiC50 mass%-Co50 mass% (Inventive Example 13), and TiC50 mass%-Fe50 mass% (Inventive Example 14). The thicknesses of each coating were 0.1 mm, 0.2 mm, 0.5 mm, 1.0 mm, 25.0 mm, 10.0 mm, 15.0 mm, and 20.0 mm. Conventional Example 11 is a mold in which a circular recess with a diameter of 5 mm is provided on the surface of the mold, and Ni with a maximum thickness of 1 mm is filled into the recess.

[0042] The number of longitudinal cracks in slabs cast using molds under each condition was measured, and the number of longitudinal cracks was measured along the slab area (1 m²). 2The longitudinal crack density was calculated by dividing by ( ). Table 3 shows the values ​​obtained by dividing the longitudinal crack density of slabs cast using each mold by the longitudinal crack density of the slabs cast using the conventional continuous casting mold of Example 11, which was used as the baseline. The number of longitudinal cracks in the slabs was measured by penetrant testing.

[0043] [Table 3]

[0044] In Table 3, a value less than 1.00 indicates that longitudinal cracking of the slab has decreased and slab quality has improved compared to conventional molds filled with Ni as the dissimilar material filling. On the other hand, a value greater than 1.00 indicates that longitudinal cracking of the slab has increased and slab quality has deteriorated compared to conventional molds filled with Ni.

[0045] As shown in Table 3, all slabs cast using the molds of Invention Examples 11 to 14 had a wettability of less than 1.00. The coatings of Invention Examples 11 to 14 have the same composition as the coatings of Invention Examples 1 to 4 shown in Table 1, and are coatings that have been confirmed to improve the wettability between the mold and the molten mold flux. From these results, it has been confirmed that improving the wettability between the mold and the molten mold flux reduces longitudinal cracking of the slab and improves slab quality. However, it should be noted that increasing the coating thickness beyond 10 mm is undesirable because it causes the surface temperature of the mold to become very high, resulting in a thinner solidified shell and making slab casting difficult. [Explanation of symbols]

[0046] 10 Continuous casting equipment 12 molds 13. Copper mold plate 14 Tan Dish 16 Cast slab support rolls 17 Conveyor Rolls 18 Molten steel 19. Molten Molding Flux 20 Immersion nozzles 22 Coating 23 Foreign substance filling section 24 Solidified Shell 26 Unsolidified layer 28 cast slabs 30 Secondary Cooling Zone 32 Slab cutting machine

Claims

1. A mold composed of multiple copper mold plates, used for continuous casting of steel, A mold in which the molten steel contact surface of the mold is covered with a coating made of TiC and nickel or a coating made of TiC and Inconel, wherein the TiC content in the coating is 10% by mass or more and 80% by mass or less, and a dissimilar material filling section is provided below the coating, in which a metal or nonmetal with a different thermal conductivity than the mold copper plate is filled.

2. The mold according to claim 1, wherein the thickness of the coating is 50 μm or more and 10 mm or less.

3. A method for continuous casting steel, comprising continuously casting steel using a mold according to claim 1 or claim 2.

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