JPH0464768B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for continuously producing a multilayer slab in which layers of different compositions are formed on a portion or multiple locations of the surface from a molten state.

[Conventional technology]

As a method for manufacturing composite steel materials by continuous casting, two immersion nozzles of different lengths are inserted into a pool of molten metal in a mold, and the discharge holes of each nozzle are set at different positions in the casting direction. , a method of injecting different types of molten metal was published in
This is proposed in Publication No. 27361. But simply 2
Simply injecting dissimilar metals at different positions in the mold in the casting direction using a standard immersion nozzle will not affect the progress of the injection, that is, no matter how much you adjust the dispensing position or the discharge flow pattern within the mold. As the process progresses, mixing of different types of molten metals occurs. Therefore, a boundary is formed where the concentration changes in the thickness direction from the surface layer to the inside of the slab. Alternatively, the boundary between the surface layer and the interior becomes extremely unclear.

Therefore, Japanese Patent Publication No. 49-44859 proposes a continuous casting method in which a refractory partition is provided between dissimilar molten metals poured into a mold. However, in order to suppress mixing of dissimilar molten metals, it is necessary to insert a sufficiently large refractory partition into the casting space. Therefore, new problems arise in casting. For example, as the refractory bulkhead gets larger, the risk of it contacting the solidifying shell increases. If this contact occurs, it may become trapped in the shell and damage the refractory, or the shell may fail and cause a breakout. Additionally, refractory bulkheads immersed in hot molten metal are
There is also a problem in terms of physical strength, and not only is the original purpose not achieved due to melting or damage during casting, but the refractory caught in the strand has a negative impact on casting work and product quality.

In order to eliminate the drawbacks of this refractory partition wall, the present inventors developed a method that utilizes a static magnetic field as a means to partition dissimilar molten metals poured into a mold, and published this method in Japanese Patent Application No. 61-252898. The application was filed as No.
In this method, a static magnetic field is created in which lines of magnetic force extend across the entire width of the slab in a direction perpendicular to the casting direction, and molten metals of different types are supplied above and below this static magnetic field as a boundary. There is. This static magnetic field acts as an electromagnetic brake, and the flow of molten metal in the static magnetic field is braked. As a result, mixing of the upper and lower layers at the position where the upper and lower layers contact can be suppressed to a minimum.

[Problem to be solved by the invention]

In this way, there is less mixing of different metals,
A multilayer slab with a clear boundary between the surface layer and the interior can be obtained. The obtained multilayer slab has, for example, an interior made of ordinary steel whose entire circumference is covered with a surface layer made of stainless steel. However, as a multilayer slab,
In addition to complete collections covered with different materials, there is a strong demand for products with a layer of different materials formed on part of the surface. For example, in rail steel, the surface layer is made of a steel material with excellent wear resistance, and the base portion is made of a steel material with excellent toughness. In addition, in structural materials, there are cases where a composite material is required, in which only one side is made of a material with excellent corrosion resistance and the other side is made of a steel material with strength.

However, according to the method described in Japanese Patent Publication No. 44-27361 or Japanese Patent Publication No. 49-44859, it is not possible to produce a multi-layer slab in which a layer of a different material is provided on a part of the surface. I can't. The same applies to the method proposed by the present inventors in Japanese Patent Application No. 61-252898.

Therefore, the present invention manufactures a multilayer slab in which a layer of different materials is formed only on a selected part of the surface by locally controlling the growth of the shell on the inner wall of the mold in a direction perpendicular to the casting direction. The purpose is to

[Means to solve the problem]

In order to achieve its purpose, the continuous casting method of the present invention applies a static magnetic field in which lines of magnetic force extend across the entire width of the slab at a position below the level of the molten metal supplied to the mold. , when continuously casting a multi-layer slab by supplying different metals above and below this static magnetic field zone, a thermal insulation zone or a heating zone extending vertically from the level of the molten metal to at least the lower part of the static magnetic field zone. The casting mold is characterized in that a tropical zone is provided at some or multiple locations of the mold.

[Effect]

In the multi-layer slab manufactured by the conventional method mentioned above, a layer of material different from the inner material is formed on the entire outer periphery because the growth of the outer shell is the same on both the front and back sides of the slab. This is because it is carried out under suitable conditions. On the other hand, in the casting method of the present invention, a thermal insulation zone or a heating zone extending vertically from the melt level to at least the lower part of the static magnetic field zone is provided at one or more locations of the mold.

FIG. 1 is a diagram for explaining the growth process of a shell produced by continuous casting of the present invention.

Immersion nozzles 2 and 3 having different lengths are immersed inside a continuous casting mold 1. Molten metals 4 and 5 of different types are injected into the continuous casting mold 1 from these immersion nozzles 2 and 3, respectively.
The molten metal 4 forming the outer layer 6 is fed into the continuous casting mold 1 through a short submerged nozzle 2 and comes into contact with the cooling surface of the mold to form a shell. This shell grows in the casting direction, that is, in the downward direction, and becomes the outer layer 6. The molten metal 5 forming the base material part 7 is
It is supplied from a long immersion nozzle 3 to the deep part of the continuous casting mold 1.

Here, in order to prevent the molten metals 4 and 5 from mixing with each other, a magnet 8 is arranged to form a static magnetic field in which lines of magnetic force act in a direction perpendicular to the casting direction. This static magnetic field brakes the flow of the molten metals 4 and 5, and suppresses disturbances at the interface between the molten metals 4 and 5. This point applies to the earlier patent application filed in 1983.
This is similar to that described in the specification of No. 108947.

In the present invention, an insulating zone or heating zone 9 is provided on the inner surface of a part of the side of the continuous casting mold 1. This insulation zone or heating zone 9 extends vertically from the level L of the molten metal 4 to at least the lower part of the static magnetic field zone in order to suppress the growth of the outer layer 6. Therefore, in the area where the insulation zone or the heating zone 9 is present, the growth of the shell that becomes the outer layer 6 is suppressed, and a slab in which the material of the base metal portion 7 is exposed on the surface is obtained. and,
By changing the arrangement of the insulation zone or heating zone 9 with respect to the continuous casting mold 1, the outer layer 6 made of a material different from the material of the base material 7 can be formed only on the required surface area of the slab. can do.

Examples of the heating zone used here include graphite molds and ceramic molds incorporating high-frequency induction heating, electric resistance heating, and the like. In addition, examples of the heat insulator include a graphite mold, a ceramic mold, and the like.

〔Example〕

As shown in the plan cross-sectional view of FIG. 2, a heating zone 9 was provided on a part of the inner surface of the continuous casting mold 1. Then, as shown in FIG. 3, which is a cross-sectional view taken along the - line in FIG.
Molten metal 4 with SUS304 composition (melting point 1450
°C) was injected. At this time, the heat removal capacity of the continuous casting mold 1 was made equal to that of a normal water-cooled steel mold. Further, as the heating zone 9, a ceramic mold incorporating electric resistance heating was used, and the temperature condition was maintained such that the molten metal 4 in the portion in contact with the heating zone 9 solidified, but the molten metal 5 did not solidify.

As a result, as shown in Fig. 4, it is possible to manufacture a multilayer slab in which the outer layer 6 with a thickness of 20 mm is formed only on one side of the slab, and the base material 7 reaches the surface on the other parts. did it. Further, at the boundary between the outer layer 6 and the base material portion 7, an interface with clearly different components and compositions was formed without the formation of brittle compounds. Therefore, even when the obtained slab was rolled to the target thickness, no peeling of the outer layer 6 was observed. Also,
Since the outer layer 6 has excellent corrosion resistance and appearance, and the base material 7 has excellent weldability, it could be used as various structural materials such as building materials.

The above example describes the case of manufacturing a two-layer stainless steel plate. However, the present invention is not limited to this, and multilayer slabs can be manufactured with the outer layer 6 provided in various states depending on the arrangement of the insulation zone or the heating zone 9 with respect to the continuous casting mold 1. be able to. FIG. 5 shows some examples.

The multi-layer slab shown in Figure a has outer layers 6 on three sides of the base material 7.
This is an example in which a continuous casting mold is provided with an insulation zone or a heating zone 9 as shown by a dashed line. The multi-layer slab shown in Figure b is an example in which an outer layer 6 is provided on a part of the surface of the base material 7. Further, the multi-layer slab shown in FIG. The multilayer slab shown in Figure d shows an example in which the outer layer 6 is formed at a plurality of locations on the surface.

In this way, by appropriately selecting the arrangement form of the insulation zone or heating zone 9 with respect to the continuous casting mold 1, the outer layer 6 can be formed at the required location of the base material portion 7.

〔Effect of the invention〕

As explained above, in the present invention, when producing a multi-layer slab by cooling and solidifying dissimilar molten metals poured into a mold, the cooling capacity along the horizontal cross section of the mold is reduced to an insulation zone or It changes depending on the heating zone. Therefore, in a part of the inner surface of the mold in the casting direction, the molten metal that becomes the outer layer solidifies to form a shell, but in other parts, a shell that becomes the base material is formed. The location where this outer layer is formed is
It can be freely adjusted by changing the arrangement form of the insulation zone or heating zone. Therefore, not only can clad steel sheets, which were conventionally manufactured by pressure welding or welding, be manufactured directly from molten metal, but also multilayer slabs with an outer layer can be manufactured for products such as rail steel and structural steel. becomes possible.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the principle of the present invention, FIGS. 2, 3, and 4 are diagrams for explaining embodiments of the present invention, and FIG. 5 is a diagram for explaining several examples regarding the formation of the outer layer. shows. 1: Continuous casting mold, 2, 3: Immersion nozzle,
4, 5: Molten metal, 6: Outer layer, 7: Base material, 8:
Magnet, 9: insulation zone or heating zone.

Claims (1)

[Claims] 1 A static magnetic field with lines of magnetic force extending across the entire width of the slab is applied at a position below the level of the molten metal supplied to the mold, and different metals are supplied above and below with this static magnetic field as a boundary. When continuously casting multi-layer slabs, a thermal insulation zone or a heating zone extending vertically from the hot water level to at least the lower part of the static magnetic field zone is provided in one or more places of the mold. A continuous casting method for multi-layer slabs characterized by: