JPS6315056B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a continuous casting method of different steel types, and more particularly to a continuous casting method of different steel types that can significantly shorten the cut-off portion of slabs due to mixing of different steel types. In continuous casting of molten steel of different steel types, when molten steel of different steel types is continuously injected into a mold using a normal method without taking any measures, a mixed portion of molten steel of different steel types is formed at the boundary between the two, It cannot satisfy any of the steel compositions and has no choice but to be disposed of as scrap. Usually its length is 3
4 m, which significantly affects the yield of molten steel, various methods have been disclosed to minimize the occurrence of such mixed slabs. In both of these methods, in continuous casting of different steel types, after the previous steel type has been cast, a so-called partition material is inserted above the melt surface in the mold to separate the previous steel type from the next steel type, and then the next steel type is cast. However,
Various materials have been proposed as this partitioning material. For example, a plate-shaped member has been proposed in Japanese Patent Publication No. 49-42215, a hollow block-shaped member has been proposed in Japanese Patent Application Laid-Open No. 54-142131, and a member having a large number of voids has been proposed in Japanese Patent Application Laid-open No. 55-1945. However, among these conventional techniques, methods using planar partitions not only have difficulty in positioning the partition when inserting the partition from above the surface of the mold, but also have difficulty in keeping the partition at the desired position even after insertion. In addition, since the partition plate is placed on the surface of the molten steel, the solidified shell generated in the mold will be cut at the partition material, resulting in the so-called breakout, where molten steel leaks from that part when the slab is pulled out. There is a flaw that causes it. In addition, in the method using a hollow block, the next time the molten steel injected into the block has solidified and the slab cannot be drawn until it has achieved a certain level of strength, so the suspension time for drawing the slab becomes longer and continuous casting is required. This causes a decrease in productivity. Further, in the case of a hollow block, there is a drawback that it is difficult to keep it in a desired position because buoyancy acts on the hollow block when it is settled in molten steel in a mold. Furthermore, as with the method using a plate having a large number of voids, there are problems in positioning and workability, as in the case of a flat plate. The purpose of the present invention is to solve the drawbacks of the conventional continuous casting method for different steel types, to provide a continuous casting method for different steel types that has excellent workability and reliability, can be performed in a short time, and has a small mixing area of both steel types. The goal is to provide the following. The gist of the present invention is that when performing continuous casting of molten steel of different steel types, after the completion of casting of the previous steel type,
From above the hot water level in the mold, insert the insert material, which has a guide member supporting the partitioning material formed into a V-shape with an acute angle on the lower side facing the hot water level and an outward opening on the upper side, below the hot water level. This continuous casting method for different steel types is characterized in that after settling until it contacts a solidified shell, the partition material is locked by the generated solidified shell and casting of the next steel type different from the previous steel type is started. That is, after the injection of the previous steel type is completed, the mixing of the previous steel type and the next steel type is prevented using a partition material whose lower surface opposite to the molten metal surface is formed into an acute angle, and which is allowed to settle below the molten metal level in the mold. be. An example of the structure of the partition material used in the present invention will be explained using the drawings. In FIG. 1, reference numeral 1 denotes a partition member formed into a V-shape with an acute angle on the lower surface facing the molten metal surface and an outwardly opened upper surface. 2 is a guide member of the partition material 1;
3 is a positioning jig for sinking the partition material 1 to a certain depth. 5 is joined with the joining jig 4,
This is a handling device for transporting and inserting insert materials. The material of the partition member 1 may be one equivalent to ordinary steel, and its dimensions and shape are preferably as shown below. Partition material thickness (T) 5 to 15 mm Vertical angle (θ) 60 to 120° Partition material width (W) Mold short side -80 mm to mold short side -40
mm Length (L) of partition material: The reason why it is desirable to have dimensions and shape of mold long side −300 mm to mold long side −50 mm or more will be described below.
The lower limit of the thickness (T) of the partition material is from the melting limit of the partition material, and the upper limit is from the weight limit due to handling of the partition material. For reference, partition material thickness (T)
Figure 2 shows the relationship between the temperature and partition material melting frequency (%).
The upper and lower limits of the apex angle θ are determined by the ease of inserting the partition material into the mold. The upper and lower limits of the width (W) and length (L) of the partition material are to reduce the gap between the partition material and the solidified shell, and are selected to appropriate values depending on the insertion depth and insertion timing. Also, if the gap between the mold wall and the mold wall is too large, it will be useless as a partition material. As the partition material, it is also possible to use commonly manufactured angle iron or the like. The guide member 2 is not limited to a plate shape as shown in FIG. 1, but may be a beam shape. Next, a method of implementing the present invention will be explained with reference to the drawings. FIG. 3 shows the state immediately after the previous steel injection was completed, the drawing was stopped, and the partition material was allowed to settle to a predetermined position from the upper surface of the molten steel in the mold. Partition material 1 is guide member 2
The positioning jig 3 is lowered along the molten steel until it contacts the upper end of the solidified shell on the upper surface of the molten steel. Unlike conventional flat plates, the partition material 1 used in the present invention has an acute angle on the surface facing the molten metal surface, so it is easy to position it on a flat surface when inserting it into the mold, and there is little resistance during insertion. Good stability even after settling. Therefore, the sedimentation work of the partition material is easy and reliable, and the time required is extremely short, 5 to 10 seconds.
In this case, the guide member 2, positioning jig 3, joining jig 4, and handling device 5 are useful from the viewpoint of workability. Further, the guide member 2 is connected to the steel type next time, and is useful for preventing the joint from coming off. FIG. 4 shows a state in which the next steel type molten steel 8 is injected immediately after settling onto the upper surface of the previous molten steel 6 of the partition material, and a solidified shell 9 has developed. 10 is a mold. Since the solidified shell 9 of the next steel type is formed continuously with the shell 7 of the previous steel type, the connection is strong and there is no fear of joint separation. Immediately after inserting the partition material, the partition material 1 and the solidified shell 7 of the previous steel type are in contact with each other, or because the dimensions of the partition material are determined so that the gap is small, the partition material 1 and the solidified shell 7 will come into contact when the next steel type injection starts. Coagulation of the area progresses rapidly. Therefore, the next time the molten steel is completely blocked at the partition material position, the range of molten steel mixing between the two steel types is limited to only on the partition plate, and the range becomes narrow. Therefore, the portion to be cut off due to incompatibility of steel types due to a mixture of different steel types becomes shorter. Table 1 shows the specifications when implementing the present invention.

[Table] In the case of continuous casting of different steel types, the casting stop time was 3 to 5 minutes when the conventional technology was implemented, but according to the present invention, the casting stop time was significantly shortened to 50 seconds. As a result, this not only improves the productivity of continuous casting, but also prevents problems with the quality of the slab that occur due to stopping casting for a long time, such as edge cracking due to overcooling of the slab, and further improves operational efficiency. Problems such as the ladle SN's single-move hole opening failure were solved, resulting in extremely large effects. FIG. 5 shows changes in composition at the joint of different steel types when the present invention is implemented. The mixing range of molten steel is 400mm from the joint to the previous steel type side and 200mm to the next steel type side, making the total 600mm very short. As a result, the cutoff length due to steel type incompatibility was shortened, and the casting yield was greatly improved. In addition, from the viewpoint of improving workability, safety problems such as prevention of molten steel scattering when inserting partition materials in the conventional technology have been solved. As described above, the present invention not only significantly shortens the mixing range of molten steel of different steel types before and after continuous casting and improves the casting yield, but also advantageously solves the drawbacks of the conventional technology and improves workability and reliability. As a result of establishing a continuous casting method for different steel types that has excellent performance and can be performed in a short time, it has greatly contributed to improving productivity, safety, slab quality, and reducing operational troubles.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the partition material used in the implementation of the present invention, Fig. 2 is a relationship between the thickness of the partition material and melting frequency, and Fig. 3 is a diagram showing the relationship between the thickness of the partition material and the melting frequency. The cross-sectional view immediately after that, FIG. 4, is a cross-sectional view when the next injection of molten steel is started and a solidified shell has developed, and FIG. 5 is a relationship diagram showing changes in components at the joint of different steel types. 1: Partition plate, 2: Guide member, 3: Positioning member, 4: Joining jig, 5: Handling device, 6:
Previous steel type molten steel, 7: Previous steel type solidification shell, 8: Next steel type molten steel, 9: Next steel type solidification shell, 10: Mold.

Claims (1)

[Claims] 1. When performing continuous casting of molten steel of different steel types, after the previous casting of the steel type was completed, a V-shape is formed from above the molten metal surface in the mold, with the lower side facing the molten metal surface having an acute angle and the upper surface side opening outward. After the inserted material with the partition material supported by the guide member is allowed to settle until it contacts the solidified shell below the molten metal surface, the partition material is locked by the generated solidified shell and casting of the next steel type different from the previous steel type is started. A continuous casting method for different steel types.