JPS5934444B2 - Direct forming method for continuously cast slabs - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for continuously casting a slab such as a bloom at a high temperature after solidification.

The continuous casting method has recently developed rapidly, and in the case of steel, it has already exceeded the production output of the steel ingot method, but the continuous casting bloom cannot be used as a final product, After cooling, it is reheated and rolled into a final product.

In order to save energy, attempts have been made to charge the steel into a reheating furnace and roll it as quickly as possible while it is still at a high temperature, but generally the capacity of the rolling mill is much larger than the continuous casting capacity, and A rolling mill becomes extremely uneconomical if the rolling order does not follow certain rules based on the finishing method, and it is not preferable to change from continuous casting to accepting charge units and rolling them continuously.

Furthermore, directly connecting a rolling mill to a continuous casting line not only increases the unbalance of capacity, but also causes thermal cracks in the rolling rolls at low speeds that match the casting speed, making it impractical.

The present invention has been made to solve the above-mentioned problems, and is characterized by the fact that an angle is provided near the area corresponding to the passage of the slab at an appropriate location upstream of the installation site of the slab cutting device of the continuous casting system. Using a plurality of reciprocally movable hammer molds pointing toward the corners of the slab in the bloom, all corners of the slab during continuous casting are simultaneously and repeatedly pointed toward the core of the slab. In addition to pressing, the pressing circumference ratio is set to 30 coefficients or more, and the present invention is to thermally open mold continuously cast bloom without reheating it on the line, and to press the internal cracks and make subsequent molding. The purpose is to prevent the occurrence of defects during rolling, and to reduce the number of mold sizes.

The molding machine used in the present invention is a forging machine that performs compression molding from all sides, and is hereinafter simply referred to as a four-way forging machine.

In the four-way forging machine of the present invention, it is desirable that the cut surface of the slab be immediately after the drawing straightening roll in the case of a dog-type continuous casting machine, or after solidification is completed in the case of a vertical continuous casting machine.

This can also be done during transportation to a cooling bed after cutting, but in this case, air may enter from the cut surface along the internal cracks.
The cracked parts are oxidized and exposed as internal defects in the final product, and the four-way forging machine creates cavities at the ends, which inevitably lowers the yield.

FIG. 1 shows an example of a four-way forging machine used in the present invention, in which a square cross-section bloom 10 is press-formed from four diagonal directions almost simultaneously toward the axis of the bloom 1 using a hammer die 2.

The anchor type 2 is connected to an axial point 5 off the center of the gear 4 by a continuous rod 3VC, and performs reciprocating motion in the bloom axis direction as the gear rotates.

Although each gear 4 may be connected to a power source whose speed is controlled individually, it is preferable to connect adjacent gears 4 by means of a gear 6 to synchronize the stroke timing.

If the gears are connected to each other as shown in Figure 1, it is only necessary to drive one of the gears.

In short, the present invention is a method in which the above-mentioned four-way forging machine is installed in a continuous casting line for square blooms, and all corner parts of the slab are compressed toward the axial center, and cracks are generated due to the compression molding. This method aims to improve internal cracks, center porosity, etc. during casting, and incidentally improve surface quality and dimensional accuracy.

Generally, steel immediately after solidification has poor deformability, and this tendency is particularly noticeable at temperatures exceeding 1250°C.

If forming is to be carried out on a continuous casting line, it is desirable to install the rolling mill or forming machine close to the continuous casting machine in order to reduce the capacity of the rolling mill or forming machine and to reduce the area occupied by these equipment. There are limitations due to the deformability of the bloom.

Forming (direct forming) of continuously cast blooms in the casting line that has been planned and studied in the past was an application of the conventional 20-roll rolling method, and compression deformation was performed from one direction, which is the roll direction.

In such a method, a large tensile stress is generated in the shaft core in a direction perpendicular to the compression direction, that is, in the direction of width expansion, resulting in internal cracks.

This tendency is exactly the same even when forging is performed alternately from directions perpendicular to each other.

In the present invention, pressure molding is performed simultaneously from all four sides, and since the suppressed circumference is long, the bloom axis is deformed only by the compressive force, and no internal cracks occur.

In order to obtain such an effect, the pressing circumference ratio must be 30% or more for each stroke, preferably 50% or more.

Here, the pressing circumference ratio is the ratio of the contact length of the anchor shape to the bloom circumference after molding, and takes the maximum value in the length direction.

FIG. 2A shows an embodiment of the present invention, in which the corners of a rectangular section bloom 10 are formed with an anchor mold 2. In such a case, a hole mold 2' is also cut in the anchor mold 2. Increase contact perimeter with bloom.

FIG. 2B shows the case where the material bloom cross section 1' is press-formed into a rectangular bloom with a cross-sectional area of approximately one half according to the present invention, and FIG. 2C shows the case where it is similarly formed into a circular bloom.

Figure 3 is a cross section taken along the line A-A in Figure 2A, and the anchor type 2 can adopt a tapered pressing surface 2'' as shown in Figure 3A, but it can also have a stepped shape as shown in Figure 3B. A suppressed surface i having a shape is most preferable.

The pressing cycle is preferably about 10 to 100 times per minute, but is not particularly limited.

A 110 mm4 low carbon killed steel manufactured by continuous casting was compared by compressing the diagonal side length to half by four-way forging of the present invention and conventional vertical forging.

In the conventional method, cracks were observed in the bloom axis, but in the method of the present invention, no cracks occurred.

The cracks in the bloom shaft core of the conventional method were caused by the forging process.

In the method of the present invention, internal cracks that had occurred during the bloom solidification process were compressed.

According to the present invention, as described above, it is possible to thermally open and mold continuously cast bloom without reheating it on the line, and without developing or generating internal cracks.
Internal cracks that occurred during the solidification process were crimped, making it possible to reduce the size of the mold.

[Brief explanation of the drawing]

Figures 1, 2, and 3 show examples of the present invention, in which Figure 1 shows the pressing situation of a square bloom by a square forging machine, and Figure 2, A shows the corner of a square bloom. In case of slight shaping, Figure 2B shows that the cross-sectional area of the rectangular bloom should be reduced to about 1/2.
FIG. 2C shows an example of a circular cross-section bloom, and FIGS. 3A and 3B show examples of an anchor-shaped bloom. 1... Bloom, 2... Anchor type, 3...
...Connecting rod, 4.6...Gear, 5...
...Axis point.

Claims (1)

[Claims] 1. Using a plurality of hammer shapes that are movable in a reciprocating manner and pointing toward the corners of the square bloom in the vicinity of the area corresponding to the passage of the slab at an appropriate location upstream of the installation site of the slab cutting device of the continuous casting equipment system,
All corners of the slab during continuous casting are simultaneously and repeatedly pressed toward the slab axis, and the pressing circumference ratio is set to 3.
A direct forming method for continuously cast slabs, characterized in that the casting rate is 0% or more.