JPS5935312B2 - Continuous casting method for medium rolling slabs - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous casting method for width rolling slabs, and more particularly to a continuous casting method for width rolling slabs, which can improve the yield of plate material by slab rolling.

Conventionally, in a method of continuously casting molten metal into a width rolling slab, a continuous casting mold as shown in FIGS. 1 and 2 has been used.

That is, in FIG. 1, a rectangular space of a Tesla slab is formed by the long side plates IA, IB and the short side plates 2A, 2B held between them.

Further, in FIG. 2, a rectangular space of the slab is formed by the long side plates IA, IB and the short side plates 3A, 3B held between them.

In the case of FIG. 1, it is the inner surface 4A of the short side plates 2A and 2B. 4B is processed into a straight planar shape, and in the case of FIG. 2, the inner surfaces 5A and 5B of the short side plates 3A and 3B are processed into a convex shape.

The cross section of a slab continuously cast using the mold shown in FIG. 1 has a shape as shown by the solid line in FIG. 3A.

This slab is rolled into a plate shape using a hot strip mill or the like, but in this case, the following disadvantages occur.

That is, the slab shown in FIG. 3A is first width-rolled by vertical rolls in the direction of the arrow (Iiyama direction of the slab) in order to regulate the width of the slab.

At this time, both longitudinal ends of the slab undergo plastic deformation due to rolling in the width direction, and only the ends rise in the Iiyama direction, resulting in a so-called dogbone shape, as shown by the broken line in FIG. 3A.

Next, it is rolled in the thickness direction by horizontal rolls, so that the central part of the end part is depressed and the top and bottom ends are bulged out, as shown in the opening in Figure 3.

Further, the rolling in the thickness direction by horizontal rolls is repeated and as the thickness decreases, the process progresses as shown in Figure 3-2, and the rolled plate ends are shaped like two plates and are cut off and discarded as defective parts. This is unavoidable, and as a result, the yield of plate material is greatly reduced.

That is, the above-mentioned tendency becomes more pronounced as the amount of width direction rolling by vertical rolls, so-called width reduction, increases.

This is because the influence of plastic deformation inside the slab during rolling in the width direction does not reach the slab gold mine, and local mass transfer occurs at both ends.

Furthermore, Japanese Utility Model Application No. 50-108915 proposes a mold in which the inner surfaces 5A, 5B of the short side plates 3A, 3B are made convex, as shown in FIG.

The purpose of this mold is to form the solidified shell on the short side of the slab into an arch shape to prevent the solidified shell on the short side of the slab from bulging during the casting process.

The end face of the slab cast using this mold has a concave shape as shown by the solid line in the third figure.

If this is rolled in the width direction by vertical rolls as shown by the arrow, it will look like the broken line in Figure 3. Similarly to the above, vertical bulges will occur at the end of the slab, resulting in a dogbone shape. This will cause a decrease in yield.

In other words, in slabs produced by conventional continuous casting methods, dogbone-like plastic deformation occurs at both ends of the slab during the initial width reduction during rolling, resulting in two-plate-like defects as rolling progresses, reducing the yield of the slab. I couldn't avoid the shortcomings.

The purpose of the present invention is to improve the shortcomings of the conventional continuous casting method for width rolling slabs, and to provide a continuous casting method for width rolling slabs that can eliminate the dogbone-like plastic deformation that occurs at both longitudinal ends of the slab during medium rolling. The purpose is to provide a method.

The objects of the present invention can be achieved by the present invention as summarized below.

The continuous casting method for width rolling slabs according to the present invention involves forming the long sides into a flat shape, forming both ends of the short sides into a straight flat shape, and forming the central part of the short sides into a concave shape consisting of a curved surface. This method continuously manufactures slabs for width rolling using a mold formed into a shape.

That is, the present invention provides a method for continuous casting of slabs for width rolling, in which the short side surface of the slab is formed into a convex shape from the beginning of casting,
This method is characterized in that the end portion of the slab does not become dog-bone-like when width-reducing the width of the slab, thereby preventing a decrease in the yield of the plate material.

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

FIG. 4 shows the general shape of the improved slab end according to the present invention.

When a slab with a convex center end face as shown by the solid line in Figure 4A is rolled in the width direction with vertical rolls as shown by the arrow, so-called width reduction, it becomes as shown in the broken line in Figure 4A,
Even if mass transfer occurs within the slab, bulges or so-called dogbone-like plastic deformation on the upper and lower surfaces of the rolled material will not occur.

Therefore, even if rolling in the thickness direction by horizontal rolls is repeated sequentially and the thickness of the rolled material decreases as shown in Figure 4, I\2,
As shown in the figure, the edges are kept in good shape and are not shaped like two plates like in the past.

No untoward phenomena will occur.

FIG. 5 shows an example of a mold used for continuous casting of slabs having such suitable shapes.

. In FIG. 5, the mold includes long side plates IA and IB and a short side plate 8A held between the long side plates IA and IB.

8B, four surfaces are formed.

The inner surfaces 9A and 9B of the short side plates 8A and 8B are formed into a concave shape having a curved surface with a predetermined curvature at the intermediate portion, and a straight flat portion remains at the corner portion 10.

The optimum value of the curvature of the concave surfaces of the inner surfaces 9A and 9B is determined in consideration of the amount of rolling in the width direction, the material of the steel to be cast, and the like.

In addition, similarly to the curvature, the dent amount △W is the amount of rolling in the width direction,
The optimum value is determined by considering the material of the steel to be cast, etc., but it is preferably selected in the range of 0.05 to 0.5 times the slab thickness D.

A slab cast using the mold thus formed can be formed into a convex surface having a predetermined curvature due to the concave curvature surface formed by the solidified shell on the short side at the center of the short side of the mold.

Therefore, even if this slab is rolled in the width direction, it is possible to prevent the occurrence of dog bones, thereby suppressing the occurrence of defects at the ends of the longitudinal plate, and greatly improving the yield of plate materials. becomes.

Furthermore, both ends (corner parts 10) of the mold short side plates 8A and 8B
Since it is formed into a straight planar shape, it is possible to prevent the occurrence of wear and damage at the corner part, and it also has the effect of preventing molten metal from leaking and improving durability. Since the solidified shell on the short side of the slab is formed into a convex curved surface with a predetermined curvature, the amount of deformation in response to the same bending force, that is, the static pressure of the internal unsolidified molten metal, is smaller than that of a conventional planar solidified shell. Become.

In other words, when subjected to the same molten steel static pressure, the amount of bulging deformation of the conventional flat plate slab is reduced, which also has the effect of preventing or reducing slab dimensional irregularities caused by bulging and various internal defects in the slab. I can do it.

Although the effects of the present invention have already been described individually, they can be summarized as follows.

(a) When continuously casting slabs from molten metal, it is possible to prevent a decrease in the yield of rolled material due to poor shape during rolling of the slab in the width direction, that is, so-called dog bones.

(b) At the same time, as a secondary effect, it is possible to reduce the luharging phenomenon in the continuous casting process.

[Brief explanation of the drawing]

Figures 1 and 2 show a cross-sectional view of a conventional continuous casting mold, and Figure 3 shows an end in the width direction of a slab cast by the conventional mold shown in Figures 1 and 2 during the rolling process. Indicates the condition of the section. FIG. 4 shows the state of the end portion in the width direction of the slab during the rolling process of the slab cast according to the present invention, and FIG. 5 is a cross section of an embodiment of the mold used in the continuous casting method for width rolling slabs according to the present invention. It is a diagram. Explanation of symbols, IA, IB... Long side plate, 2A. 2B, 3A, 3B, 8A, 8B...Short side board, 4
A. 4B, 5A, 5B, 9A, 9B... Inner surface of short side plate, 10... Corner part.

Claims (1)

[Claims] 1. In a continuous casting method for width rolling slabs, in which a slab to be rolled in the Iiyama direction is manufactured using a mold having a long side surface and a short side surface, the long side surface is formed into a flat shape. A continuous casting method for a slab for width rolling, characterized in that a mold is used in which both ends of the short sides are formed in a straight planar shape and a central part is formed in a concave shape with a curved surface.