JPH04138852A - Method for protecting mold at initial stage of pouring in twin belt continuous casting - Google Patents

Abstract

PURPOSE:To stably cast a cast strip by setting a metallic net between the wall face of long side mold and a pouring nozzle at the time of starting casting and releasing the direct hitting of molten metal discharged from the nozzle to the long side mold wall. CONSTITUTION:The metallic net 3 acts as a resistant body to a molten metal flow discharged from a flat type pouring nozzle 4, and by this, the direct hitting of discharged flow to the long side mold wall is relaxed. By using the metallic mold without using a metallic plate, as the molten metal penetrates into the metallic net, the formation of air gap can be prevented. The metallic net selects the material, net shape, size, etc., so as not to impart an unfavorable influence to a solidifying process, solidified structure, component composition, etc., in the cast strip according to kind of cast metal. In the case of casting the steel, this is suitable to use steel-made net plate, etc. By this method, the operation trouble of heat damage, etc., of the mold caused by the direct hitting of the discharged molten metal to the mold wall and the abnormality in the quality in the cast strip attending on it are prevented and the cast strip can be stably cast.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for protecting long side mold walls during the initial pouring period of twin-belt continuous casting, particularly during the idle pouring period in which pouring is performed with the dummy par head stopped. .

In the twin-belt continuous casting method, molten metal is injected between the walls of a movable mold, which consists of a pair of cooling belts arranged facing each other in parallel at intervals corresponding to a predetermined slab thickness. This is a continuous casting method in which casting is performed in synchronization with the drawing speed of , and is particularly suitable for casting slabs with a thickness of about 10 mm at high speed.

[Conventional technology]

Conventionally, in order to manufacture thin metal sheets such as cold-rolled 1iI sheets using continuous casting, the mold is vibrated in the casting direction and the thickness is 10 mm.
After casting into slabs with a temperature of 0 or higher, the surface of the resulting slabs is treated, heated to over 1000°C in a heating furnace, and then hot rolled by a hot strip mill consisting of a rough rolling mill row and a finishing rolling mill row. After applying hot strip annealing and pickling to remove surface scale as necessary, cold rolling was performed.

If a twin-belt continuous casting method is applied in place of the conventional continuous casting method in such a thin metal sheet manufacturing process, a thin slab slab with a diameter of several tens of holes can be obtained, which is suitable as a material for finishing hot rolling. As a result, it is possible to omit the rough rolling step of hot rolling and the heating furnace therefor, and a significant improvement in production cost and productivity is expected.

[Problem to be solved by the invention]

In twin-belt continuous casting, molten metal is injected between a pair of cooling belts facing each other, but since the distance between the cooling belts facing each other is as narrow as several tens of millimeters depending on the thickness of the slab, the injection nozzle (
The molten metal flow discharged from a thin flat nozzle is particularly likely to directly hit the mold wall on the long side. This phenomenon is particularly noticeable in the unsteady part where the molten metal level has not yet risen in the early stages of casting, i.e. in the unsteady pouring part where the dummy head is stopped and poured. It is necessary to reliably prevent thermal damage, etc., as it may hinder the continued stable casting.

In conventional continuous casting in which thick slabs of 100 mm or more are cast using a vibrating mold, the distance between the mold wall and the nozzle is quite large. Therefore, the problem of direct hitting the mold wall due to the discharge flow from the nozzle did not occur, and it was sufficient to place the coolant as a cushion on the upper surface of the dummy bar head. However, such conventional means cannot be applied to twin-belt continuous casting where the distance between the nozzle and the mold wall is very small, and it was necessary to develop a completely new method of protecting the mold wall.

The present invention solves the above-mentioned problems specific to the twin-belt continuous casting method by alleviating the direct impact on the mold wall by the discharged molten metal flow in the pouring section at the start of casting, preventing thermal damage to the mold, and stabilizing the mold. The purpose of the present invention is to provide a method for protecting a mold that allows continuous casting.

[Means to solve the problem]

According to the present invention, the above object is achieved by arranging a metal mesh between the long side mold wall surface of the pouring part at the start of casting and the casting nozzle, so that the long side mold wall surface of the molten metal discharged from the nozzle is This is achieved by a method of protecting the mold at the initial injection stage of twin-belt continuous casting, which is characterized by mitigation of direct impact.

[Effect]

In the present invention, the metal mesh acts as a resistor against the molten metal flow discharged from the nozzle, thereby alleviating the direct impact of the discharge flow on the long side mold wall.

The reason why a metal net is used instead of a metal plate is that if the former is used, the molten metal will not be inserted sufficiently between the mold and the metal plate, creating an air gap, which will cause serious operational problems such as breakouts due to poor solidification. This is because it causes

If a metal mesh is used, the formation of the air gap described above can be prevented because the molten metal passes through the metal mesh.

The material, mesh shape, dimensions, etc. of the metal mesh are selected depending on the type of metal to be cast so as not to adversely affect the solidification process, solidification structure, component composition, etc. of the slab.

For steel casting, copper mesh plates etc. are suitable.

In the following, the invention will be explained in more detail by means of examples with reference to the accompanying drawings.

〔Example〕

FIG. 1 shows an example of mold protection according to the present invention in double-belt continuous casting of steel. 3A is a side view of the pair of cooling belts 1 viewed from the side edge direction, and FIG. 1B is a front view of the cooling belts 1 viewed from the belt surface.

A pair of cooling belts 1 constitute long side mold walls, and a dummy bar head 2 inserted between these cooling belts 1 constitutes a mold bottom. A steel mesh plate 3 (for example, porosity: about 60%, mesh size: about 2 mm) is placed on the upper surface 21 of the dummy bar head 2.

A flat casting nozzle 4 is inserted approximately in the center between the cooling belts 1, and the molten metal is discharged from its tip 41, falls onto the upper surface 21 of the dummy bar head 2, and is scattered laterally. Further, the discharge stream from the nozzle tip 41 falls while slanting to some extent in the lateral direction in FIG. 2(a). Both the scattering flow and the construction method flow of the falling molten metal are resisted by the mesh plate 3, and the portions that pass through the mesh plate hit the long side mold walls of the cooling belt 1.

Thereby, direct impact on the long side mold wall 1 can be alleviated without forming an air gap between the mesh plate 3 and the long side mold wall 1.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to industrially stably cast thin slab slabs by preventing operational troubles caused by heat damage to the mold due to direct impact of the discharged molten metal on the mold wall, and the resulting irregularities in slab quality. I can do it.

[Brief explanation of drawings]

FIG. 1 shows an example in which the mold protection method of the present invention is applied to double-belt continuous casting of steel, in which (a) is a side view seen from the side edge of the cooling belt, and (b) is a side view of the cooling belt. It is a front view seen from the surface. 1... Cooling belt, 2... Dummy par head, 3... Metal mesh, 4... Flat pouring nozzle. or

Claims (1)

[Claims] 1. By arranging a metal mesh between the long side mold wall surface of the pouring section at the start of casting and the casting nozzle, the direct impact of the molten metal discharged from the nozzle on the long side mold wall is alleviated. Mold protection method during the initial injection stage of twin-belt continuous casting.