JPH0332420B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a method for directly and continuously casting wide thin plates from molten metal, especially molten steel, using a surface moving mold that moves synchronously with the slab.

In continuous casting of nets, a proposal has been made to manufacture a wide thin plate by direct casting instead of the conventional thick slab. For example, an invention for directly manufacturing thin plates from molten steel using a synchronously rotating mold consisting of twin rolls or twin belts was published in Japanese Patent Application Laid-Open No.
No. 55-75862, JP-A-57-9566, JP-A-58-
32548 and Japanese Patent Application Laid-Open No. 58-32551. The basic principle of these is that, as shown schematically in Figure 1, casting is performed by a pair of cooled casting rolls (or casting belts) placed opposite each other with a predetermined gap corresponding to the thickness of the slab. surface-moving molds 1a, 1b, and the width of slabs placed oppositely on top of the surface-moving molds 1a, 1b with a gap corresponding to the width of the slab, which is within the width of the surface-moving molds 1a, 1b. A pair of fixed walls 2a, 2b for regulation
(In the figure, these fixed walls 2a and 2b serve as two side walls for forming a sump container.)Thin plate slabs are continuously cast by this method.

There are various problems in realizing continuous casting of thin plates using such a moving surface mold, but among them,
Non-uniform cooling rate in the width direction of the slab (fixed wall 2a,
2b) (both sides of the slab cool at a faster rate), problems such as uneven plate thickness, lamination, and wrinkles, as well as the problem of molten steel seizing on the surface of the moving mold, can be solved. The big issue is how to solve this problem.

The present invention has been made with the aim of solving such problems, and it uses a moving mold surface formed by a pair of casting rolls or casting belts that are arranged facing each other with a predetermined gap corresponding to the thickness of the slab. In a method of continuously casting thin plate slabs by continuously supplying molten metal, the surface of the movable mold that will come into contact with the molten metal is roughened, and the roughened surface of the movable mold before it comes into contact with the molten metal is Continuous casting of a thin plate slab, characterized in that a coating agent formed into a solid state is fed out under a predetermined pressure, and the coating agent is held in the recesses of the roughened surface while being ground by this feeding. The present invention provides a method.

FIG. 2 shows an example in which the method of the present invention is applied to a moving surface mold using casting rolls, and similar to FIG. A pair of cooled casting rolls rotating in opposite directions (hereinafter referred to as moving mold surfaces 1a and 1b) are placed oppositely on the moving mold surfaces 1a and 1b with an interval corresponding to the width of the slab 3. This figure shows an example in which a thin plate continuous casting mold is constructed by fixed walls 2a and 2b. The fixed walls 2a, 2b for regulating the width of the slab form one side wall forming a sump container with the long side walls 4a, 4b arranged orthogonally thereto on the movable mold surfaces 1a, 1b. It's summery. The long side walls 4a, 4b are
It plays the role of retaining a sufficient amount of molten metal while preventing the backflow of molten metal to the moving mold surfaces 1a and 1b that are about to head towards the casting space. In the case of equipment that forms deep valleys that can hold ), this long side wall 4
In some cases, a sump vessel can be formed using only fixed walls 2a, 2b and movable mold surfaces 1a, 1b without requiring parts a, 4b.

In any case, the present invention is such that the moving mold surfaces 1a and 1b are brought into contact with a solid coating agent under a predetermined pressure before being moved to the area where they will come into contact with the molten metal. do.
In the example shown in FIG.
An example is shown in which the end of b is made to its full width and is pressed against the moving mold surfaces 1a and 1b before contacting the molten metal. At that time, apply coating agent 5 as shown.
It is preferable to use molds 6a and 6b that extrude a and 5b into plate shapes. In the process of extruding through the molds 6a and 6b, the coating agent raw material can also be formed into a solid shape.

The coating agents 5a and 5b are those that provide an anti-seize effect between the molten metal and the movable mold surfaces 1a and 1b, more specifically, those that form a film that provides a lubricating effect or a slow cooling effect. Good to use. For example, fine powder graphite baked with clay or other binders, solid oils and fats,
Highly viscous silicone oils and fats can be used singly or in combination and molded into a solid shape. Such solid coating agents 5a, 5b
During casting operation, a uniform film having a width that satisfies the width of the slab is formed on the surface of the moving mold by pressing it under a predetermined pressure against the surfaces 1a and 1b of the moving mold before moving into the casting space. The coating agent 5a, 5b is formed continuously, and the molten metal is always coated with the coating agent 5a, 5b.
solidification will begin upon contact with the moving mold surface, which is uniformly coated over its entire surface. Therefore, due to the existence of this uniform film, even at the beginning of solidification, the occurrence of temperature differences depending on the location is alleviated (the phenomenon that the cooling rate becomes faster on the side of the fixed walls 2a and 2b is alleviated). At the same time, the solidification shell will be prevented from partially scorching with this moving mold surface.

In particular, in the case of the present invention, the solid coating agents 5a and 5b are moved to the mold surface 1 under a predetermined pressure.
Since it is pressed against surfaces a and 1b, a strong coating layer with a uniform thickness can be formed compared to simply applying a liquid lubricant or the like, and the above-mentioned slow cooling effect and anti-seizure effect can be effectively exerted. This coating agent can also perform a sealing action to prevent hot water from entering the gaps between the fixed walls 2a, 2b, and further between the long side walls 4a, 4b and the movable mold surfaces 1a, 1b. It also has a beneficial effect in avoiding the occurrence of solidified shells of irregular shape and troubles caused by pouring in hot water. In order to obtain such an effect, it is necessary to finish the surface of the moving mold to an appropriate degree of roughness over the area to be coated. That is, depending on the type of material to be coated, the surface of the moving mold may be finished to a roughness suitable for increasing the adhesion strength when the material adheres to the surface of the moving mold.

In this way, when the solid coating agent is pressed against a rough surface with appropriate roughness and sent out, the coating agent is transferred to the recesses of the rough surface while being continuously ground, and the coating agent is uniformly transferred to the mold surface. The long side walls 4a, 4b are coated and before the surface of the mold that comes into contact with the molten metal is coated with the molten metal.
Even if the long side walls 4a and 4b come into contact with the rough surfaces, since the surface of the mold is smoothed by the coating agent bitten into the recesses, the long side walls 4a and 4b are prevented from being ground by the rough surfaces. The coating agent bitten into the recessed portions is brought to a point where it comes into contact with the molten metal without being scraped off by the long side walls 4a, 4b. According to the tests conducted by the present inventors, the roughness of the rough surface formed on the moving mold surface is generally Ra = 14 to 20μ.
It was found that approximately m is appropriate.

Although the above description has been made regarding the case where the casting roll is used as the moving mold surface, the method of the present invention can be implemented in the same manner even in a thin plate continuous casting apparatus configured with an endless casting belt as the moving mold surface.

As described above, according to the present invention, a uniform and strong coating layer can be effectively interposed between the molten steel and the surface of the moving mold, particularly in direct continuous casting from molten steel to a steel plate using the twin roll or twin belt method. This will greatly help prevent changes in thin plate thickness and lamination caused by differences in cooling rates, which have been regarded as problems, as well as surface defects such as surface cracks in slabs, and will also prevent the solidification shell from moving. It also prevents the surface of the mold from seizing, greatly contributing to operational stability and preventing damage to the surface of the moving mold (surface cracking, crazing).

[Brief explanation of the drawing]

FIG. 1 is a schematic perspective view showing a typical conventional example using a surface moving mold, and FIG. 2 is a schematic perspective view showing an example in which the method of the present invention is applied to continuous thin plate casting using a twin roll method. 1a, 1b... moving mold surface, 2a, 2b...
Fixed wall, 3...Thin slab, 4a, 4b...Long side wall, 5a, 5b...Coating material, 6a, 6b
...Mold for coating material.

Claims (1)

[Claims] 1. Continuously casting thin plate slabs by continuously supplying molten metal to the surface of a moving mold formed by a pair of casting rolls or casting belts placed opposite each other with a predetermined distance corresponding to the thickness of the slab. In the method of 1. A continuous casting method for a thin plate slab, characterized in that the coating agent is held in the recesses of the roughened surface while the coating agent is ground by the feeding.