JPS62289352A - Production of block mold for shifting block type continuous caster - Google Patents

Abstract

PURPOSE:To extend the service life of a mold and to improve the quality of cast sheet by making the block mold by steel, forming it to beforehand larger than the prescribed size and executing the finish work after repeating the thermal loading and cooling operations alternately. CONSTITUTION:The block mold 1 is formed by steel as the material and as a little larger than the prescribed size. By selecting the suitable heat source, the block mold is heated to become to more than at least 10<6> W/m<2> thermal loading for mold surface area, and then cooled by air or water cooling. After repeating this operation at one or more times, the finish machining is executed to form the block mold 1'. As the mold 1' beforehand repeats plastic deformation by the surface thermal loading, at the time of contacting with the molten metal, the plastic deformation of the mold scarcely occurs. Therefore, flatness of the casting surface 2 ' is held for a long term. As the mold is made of steel, the cooling condition of the cast sheet is improved. In this way, the service life of the mold is extended, and the quality of the cast sheet is improved.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a method for manufacturing a block mold in a moving block continuous casting machine that continuously casts slabs from molten metal. .

[Prior Art] Generally, a moving mold type continuous casting machine forms a mold by connecting a large number of block molds a in an endless track as shown in FIG.
A mold space C is created by combining the molds vertically, a tundish nozzle d is inserted into one opening in the mold space C, and the melt 1e is supplied from the tundish nozzle d,
Further, casting is performed continuously while avoiding the movement of the coolable mold and the solidified slab f toward the other open end.

The block mold a is made of copper, which has good thermal conductivity, in order to quickly cool the molten metal e in the mold space C and prevent thermal deformation of the block mold a.

[Problems to be Solved by the Invention] However, when a mold consisting of a copper block mold a is continuously cast, the slab f in the mold space C comes into contact with the block mold a as shown in Fig. 4. The surface is further cooled and solidified shell g
becomes thicker.

The thicker part of the solidified shell 9 shrinks due to heat, and the slab f during cooling
The surface of is indented.

Since the recessed part cannot come into contact with the block mold a, it is cold! The other parts are cooled and the solidified shell of the other parts becomes thicker.

As the slab f moves through the mold C while repeating this phenomenon, the surface of the final cast slab f is formed with many fine irregularities, and the quality is not sufficient. It wasn't necessarily a thing.

[Means for Solving the Problems] In order to solve the problems of the conventional art, the inventors of the present invention have conducted various studies, and found that by using steel with slightly low thermal conductivity as the material of the block mold a, the slab can be It has been found that it is possible to uniformly cool f.

However, the steel block mold a' has a slightly low thermal conductivity, which increases the thermal gradient, causes plastic deformation due to large thermal stress, and has the disadvantage that it becomes unusable after the -th pouring of molten steel. was.

As a result of further studies on steel block molds, the inventors of the present invention found that the difference in height between the center point a' of the steel block mold and point B at the outer circumferential end is the relative deformation as shown in FIG. In this case, the relationship between the number of castings and the relative deformation is as shown in Fig. 6, and the number of castings of 2 to 3 times is the same as that of the steel block mold a'
It was found that plastic deformation due to thermal stress almost disappeared. Based on this knowledge, we came up with the idea that the steel block mold a' should be subjected to a heat treatment to the same extent as casting beforehand and then subjected to the final processing, and we completed the present invention.

That is, the present invention provides a moving block type continuous casting machine, which is characterized in that a block mold formed of steel larger than a predetermined size is subjected to a cooling operation at least once after applying a heat load, and then subjected to final processing. This involves a block mold manufacturing method.

[Function] Since the material of the block mold is steel, the thermal conductivity is slightly lower, so a moderate cooling effect can be obtained, and the piece can be cooled uniformly.

Since the steel block mold is heat treated in advance and then subjected to finishing processing, there is almost no plastic deformation and it can be used for a long period of time.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a process diagram of the method of the present invention, in which a block mold 1 is formed of steel to be slightly larger than a predetermined size, and a heat load is applied to the casting surface 2 of the block mold 1.

The heat load is calculated by the contact time between the molten metal and the block mold (when the temperature of the molten Q (molten steel) in continuous casting is 1600°C).
sec) and the heat load (W/m2) on the block mold as shown in Figure 2, so at least 106
This is applied by selecting a heat source to provide a mold surface area heat load of W/m2 or more and heating for about 10 seconds (or more).

After heat load, cool by air or water cooling.

Shun repeats the above operations at least once or twice, and finally finishes the piece by cutting it using a machine.

A large number of block molds 1' made in this manner are connected and wound around the rolls separated by 10 times to form a trackless mold, and the trackless molds are moved in the same direction by opposing surfaces. Molten metal is supplied through a tundish nozzle inserted into the mold space, and is cooled and solidified using a block mold to cast a slab.

The block mold 1' that comes into contact with the molten metal undergoes repeated plastic deformation due to the surface heat load, and almost no plastic deformation occurs, so even if it comes into contact with the molten metal and receives a new heat load, almost no plastic deformation occurs, and the block mold 1' The flatness of the ID surface 2' of the mold 1' is maintained and can be used repeatedly.

In addition, since the block mold is made of steel, its thermal conductivity is slightly lower than that of copper, so the rate at which the solidified shell of the slab in the mold space is formed is appropriate, and the thickness of the solidified shell is uniform. Become. Therefore, the surface of the slab in the mold space becomes uniform, and it is less likely that the slab will separate from the block mold surface due to thermal distortion, and slabs with uniform surface properties will be continuously produced. The cooling efficiency of steel block molds is almost the same as that of copper molds because the steel block molds are always cooled uniformly in close contact with the molds.

It should be noted that the method for manufacturing a block mold for a moving block type continuous casting machine of the present invention is not limited to the above-described embodiments, and it goes without saying that various changes can be made without departing from the gist of the present invention. .

[Effects of the Invention] As explained above, according to the block mold manufacturing method of the moving block double casting machine of the present invention, various excellent effects as described below are exhibited.

<I) Since the block mold is made of steel and has been subjected to heat treatment at a level equal to or higher than the heat load during continuous casting, the plastic deformation of the book mold that occurs during continuous casting is minimal, making it easy to repeat. can be used.

<n> Since a steel block mold can be used, the slab can be cooled uniformly due to steel having a slightly lower thermal conductivity than copper, and slabs with uniform surface properties can be continuously cast. Can be done.

[Brief explanation of the drawing]

Figure 1 is a process explanatory diagram of the method of the present invention, Figure 2 is a diagram showing the relationship between the molten steel-mold contact time and the amount of heat load per unit area on the mold in the method of the present invention, and Figure 3 The figure is an explanatory diagram of an example of a conventional moving block type continuous casting machine, Figure 4 is an explanatory diagram of a slab continuously cast by the continuous casting method shown in Figure 3, and Figure 5 is the diagram shown in Figure 3. FIG. 6 is a diagram showing the relationship between the number of castings and the relative deformation of the steel block mold shown in FIG. 5. 1.1' is a block mold, 2, 2' is a casting surface.

Claims (1)

[Claims] 1) A block mold for a moving block type continuous casting machine, which is characterized in that a block mold formed of steel larger than a predetermined size is subjected to a cooling operation after applying a heat load one or more times, and then subjected to final processing. Production method.