JP2641233B2 - Method of manufacturing beam blank in continuous casting - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a beam blank in continuous casting, and more particularly, to continuous casting cast into a normal rectangular cross section without using a special mold. The present invention relates to a method in which a slab can be easily formed on a beam blank as a material of an H-section steel in a continuous casting line.

<Prior art> Conventionally, regarding the manufacture of a beam blank as a material of an H-section steel, means for directly manufacturing an H-shaped slab by a continuous caster;
Means are known in which a rectangular billet or bloom is manufactured by a continuous casting method or a lump method, and is rolled by a caliber roll or the like in a rolling step. Also, in particular,
In the case of producing a large H-section steel, a method of rolling from a continuously cast slab has been proposed and implemented.

<Problems to be Solved by the Invention> As means for producing a beam blank with the former continuous caster, there are, for example, those disclosed in JP-A-52-13428 and JP-A-52-13430. As shown, the mold 10 is formed into an H shape and the beam blank 11 is directly cast. However, since the shape is complicated, casting is not easy, and
Since the slab support mechanism from the start to the completion of solidification of the slab 11 becomes complicated, the equipment cost, running cost, maintenance cost, and the like of the continuous caster are considerably higher than those of a normal continuous caster. Further, when producing H-shaped steels of various sizes, two or more types of molds 10 for the beam blank are required, and the above problem is further increased.

The latter means of rolling billets, blooms or slabs is a more general means, but as much as the material shape and product shape are different, the degree of work in rolling, the number of steps increases, and the production cost is more than the former. Will be inferior. Also,
As disclosed in Japanese Patent Application Laid-Open No. 56-4302, there is a method of forming a beam blank by pressing down both ends with a head, but it is difficult to work to a predetermined shape.

An object of the present invention is to provide a method for easily and inexpensively manufacturing a beam blank for an H-section steel in view of the above situation.

<Means for Solving the Problems> In order to achieve the above object, the present invention relates to a method for producing a beam blank from a continuous cast slab having a rectangular cross section cast by continuous casting. A forging device having a pair of protruding dies corresponding to the blank shape is installed, and the pair of protruding dies are subjected to the following conditions from both front and back surfaces of the continuous cast slab having an unsolidified portion, γ = σ /d≧0.75 (1-f _so ) where γ: Reduction rate for unsolidified thickness σ: Reduction amount of continuous cast slab d: Unsolidified thickness at rolling position f _so : Solid of unsolidified shaft center at rolling position By reciprocating in the slab thickness direction under the phase ratio,
This is a method for producing a beam blank in continuous casting, characterized by continuously reducing the pressure.

Further, the present invention provides a forging method comprising a pair of protruding rolls corresponding to a beam blank shape in a continuous casting line, instead of the pair of protruding dies, when the amount of reduction with respect to the continuous cast slab is relatively small. The apparatus may be installed, and the pair of projecting rolls may be used to continuously lower the continuous cast slab having unsolidified portions in the thickness direction of the slab from both front and back surfaces under the above conditions.

<Operation> When the beam blank is directly cast by the continuous caster, the continuous caster becomes complicated as described above, and cannot have a variety of sizes. In addition, if all molding is performed in the rolling process, the rolling cost increases. Therefore, the present invention eliminates the disadvantages of the two and combines the advantages by forging a continuous cast slab having a rectangular cross section in a continuous caster in a thickness direction with a pair of projection-type dies. Alternatively, a beam blank is formed by pressing down with a pair of projecting rolls.

In this case, when the slab is processed in a state having an unsolidified portion, the processing can be performed with a considerably smaller force as compared with normal rolling, and a heating step at the time of processing can be omitted, so that the number of heat source units can be reduced. Although internal cracks may occur in the slab depending on the rolling conditions, this can be prevented by appropriately selecting the rolling conditions described above.

<Example> Hereinafter, the present invention will be described in detail based on examples.

The present invention provides a forging device in a line of a continuous casting facility, and forges a billet or bloom cast into a rectangular cross section in a casting process, thereby enabling efficient production of a beam blank with a small rolling force. Fig. 1 ~
FIG. 4 shows one embodiment.

FIG. 1 shows a schematic configuration of the present invention. A continuous cast slab 1 is cast by a mold 3 having a rectangular cross section similar to that of a normal continuous caster. Is provided. The forging device 4 has a pair of dies 5, 5 'which are provided opposite to each other with the slab 1 interposed therebetween, and the dies 5, 5' are moved in the thickness direction of the slab 1 shown by arrows in the drawing. The casting 1 is continuously forged by reciprocating.

The shape of the molds 5, 5 'has convex projections 5a, 5a' at the center in the cross-sectional direction as shown in FIGS. 2 to 4, respectively. By forging from the previous state to the state after the reduction of the slab shown in FIG. 3, an H-shaped beam blank is manufactured from a rectangular slab. In this case, when the upstream side of the pressing surface is formed in a tapered shape as shown in FIG. It is desirable to have a shape.

The forging position of the slab 1 is preferably reduced in a state where the unsolidified portion 1b exists in the slab 1 from the viewpoint of reducing the rolling force. However, in this case, if the rolling conditions are not properly selected, internal cracks may be generated in the slab 1 due to internal strain caused by rolling. In order to prevent this, it is basically necessary to press-bond the solid phase portion of the unsolidified portion and set the press-bonded surface to a compressive stress field.

That is, assuming that the thickness of the unsolidified portion in the reduction portion of the slab 1 is d, the solid phase ratio of the shaft core portion is f _so , and the reduction amount is σ, the unsolidified portion 1b which is the reduction portion has a dendritic solid phase. since the liquid phase is mixed average solid fraction of the unsolidified portion 1b is the axial center solid phase ratio f _so as solidified portion 1b
Is the average of the solid phase ratio 1 at the interface with And the average liquid phase ratio of the unsolidified portion 1b is Can be expressed as Becomes Therefore, in order to lower the liquid phase portion 1b and press-bond the solid phase portion 1a, it is sufficient to adopt a reduction amount sufficient to extrude the liquid phase portion 1b by pressing, and basically, the equivalent liquid phase thickness If it is reduced by the amount of reduction described above, pressure bonding is performed.

However, in order to make the pressure contact surface a compressive stress field, further reduction is necessary, and the reduction amount σ given from the outer surface of the slab does not act effectively as the reduction amount of the unsolidified portion. In order to prevent internal cracks, it is necessary to allow for a margin coefficient k in the reference value. That is, assuming that the required rolling reduction for the unsolidified portion is γ = σ / d, k depends on the thickness h ₀ , h before and after the reduction of the slab,
From the experimental results, it has been found that k = 1.5 to 2 in the ordinary billet and bloom shapes. Therefore, the conditions for preventing internal cracks are as follows, for example, with k = 1.5.

As described above, the rolling position of the slab 1 is desirably reduced at an unsolidified portion satisfying the expression (1).

Although the forging device has been described by taking the forging device 4 as a representative example, as another embodiment, the forging device is used to reduce by using a pair of projecting rolls 6, 6 'as shown in FIG. 5 and FIG. You can also. For a normal beam blank, the slab thickness h ₀
Therefore, forging is desirable, in which a large reduction can be performed relatively easily. It can be pressed.

In the above-described embodiment, the description has been given of the case in which one set of the mold with projection or the projection-like roll is provided.
Multiple sets or more can be arranged.

<Effects of the Invention> According to the present invention, the following effects can be obtained.

1) Since the slab can be formed in an unsolidified state in which the slab is easily deformed, the slab can be formed with small energy, and the manufacturing cost of the beam blank can be reduced.

2) If the forging die or the protruding roll has various sizes, beam blanks of various sizes can be manufactured from the usual rectangular mold size (single or plural),
Equipment costs and operating costs can be reduced as compared to holding various dedicated beam blank molds.

3) It can be easily installed in a normal billet or bloom continuous caster, and can be easily changed from a conventional existing continuous caster to a beam blank continuous caster.

[Brief description of the drawings]

FIG. 1 is a schematic structural view showing an embodiment of the present invention, FIGS. 2 to 4 are explanatory diagrams showing a state of casting slab reduction by a forging die of the present invention, and FIG. 5 is another embodiment of the present invention. FIG. 6 is a cross-sectional view showing a state where a slab is reduced by a protruding roll of the present invention, and FIG. 7 is a cross-sectional view showing a conventional example. DESCRIPTION OF SYMBOLS 1 ... Continuous cast slab, 1a ... Solid shell, 1b ... Unsolidified part, 4 ... Forging device, 5 ... Forging die, 5a ... Protrusion, 6 ... Protrusion roll.

Claims (2)

(57) [Claims] 1. A method of manufacturing a beam blank from a continuous cast slab having a rectangular cross section cast by continuous casting, comprising: a forging device having a pair of projection-shaped dies corresponding to a beam blank shape in a continuous casting line. Installed, the pair of protruding dies are continuously lowered by reciprocating in the slab thickness direction from the front and back surfaces of the continuous cast slab having an unsolidified portion under the following conditions. A method for producing a beam blank in continuous casting. Note γ = σ / d ≧ 0.75 (1-f _so ) where γ: Reduction rate for unsolidified thickness σ: Reduction amount of continuous cast slab d: Unsolidified thickness at reduction position f _so : Unsolidified axis at reduction position Solid fraction of core 2. A method for manufacturing a beam blank from a continuous cast slab having a rectangular cross section cast by continuous casting, wherein a forging device having a pair of projecting rolls corresponding to the beam blank shape is installed in a continuous casting line. Then, in the continuous casting characterized by continuously rolling down from the front and back surfaces of the continuous cast slab having a non-solidified portion in the pair of projecting rolls, under the following conditions in the slab thickness direction Manufacturing method of beam blank. Note γ = σ / d ≧ 0.75 (1-f _so ) where γ: Reduction rate for unsolidified thickness σ: Reduction amount of continuous cast slab d: Unsolidified thickness at reduction position f _so : Unsolidified axis at reduction position Solid fraction of core