JPH11254002A - Production of round steel from large cross sectional stainless steel cast bloom as blank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the productivity and the yield and to save the energy consumption by applying an electromagnetic stirring device in a mold using a stainless steel cast bloom, in which light rolling reduction is executed to the cast bloom at the end stage of solidification as a blank, and producing a round steel having >= a specific diameter in a forging process, followed by a hot-rolling process. SOLUTION: For example, the SUS316 cast bloom having 390 mm×480 mm cross sectional dimension, in which the electromagnetic stirring in the mold is applied and the light rolling reduction is executed to the cast bloom at the end stage of the solidification to reduce the porosity, is heated to a prescribed temp. in a heating furnace. For example, this bloom is preformed to 300 mm×400 mm cross sectional dimension with a two column pull-down type hydraulic press, and after eliminating the porosity at the center part, i.e., the reheating is executed to apply the hot-rolling into the round steel having >=150 mm diameter. In this way, the sp. gr. at the center part is made to almost the same sp. gr. in the vicinity of the distance of about 1/4 of the diameter from the outer periphery, and the porosity is eliminated and the effect of the forging process is sufficiently obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention eliminates the porosity defect existing in the center of the cross section of a stainless steel continuous cast material having a large cross section having a large deformation resistance in a forging process, and a diameter of 150 mm or more in a subsequent hot rolling process. The present invention relates to a method for producing round steel using a large-section stainless steel slab for mass-producing round steel at low cost.

[0002]

2. Description of the Related Art Conventionally, a large section (for example, 390 mm × 48
0 mm), the bridging starting from solidification shrinkage and columnar crystals is formed at the center of the cross section of the continuous cast material of stainless steel, so that the molten metal cannot be sufficiently supplied to the final solidified portion at the center of the cross section. , Porosity exists. As a method of eliminating this porosity, an electromagnetic stirring device in the mold is applied, the tip of the columnar crystal generated at the solidification interface is cut, and the number of equiaxed crystals is increased from that point, which occurs at the end of solidification. The generation of bridging is suppressed to compensate for the shortage of supply of molten metal, and the porosity is reduced.

As shown in FIG. 3, a slab in the final stage of solidification in continuous casting is gradually reduced in steps using two pairs of multi-stage rolls different from pinch rolls. There is a method of reducing the voids generated due to solidification shrinkage while preventing internal cracks of the slab by reducing the pressure.

[0004]

However, for example, SUS316 stainless steel having a large cross section (390 mm × 480 mm) having a large deformation resistance is subjected to an electromagnetic stirring device in a mold, and as shown in FIG. The porosity at the center of the slab is not completely eliminated even when the single-sided reduction is performed.
For this reason, a round steel having a large forging ratio and a diameter of less than 150 mm can be pressed with porosity in the hot rolling step.
In the above round steel, the porosity cannot be completely eliminated only by the hot rolling process, and the round steel is actually manufactured by a forging process instead of the hot rolling.

[0005]

In order to solve the above-mentioned problems, a means for solving the problems of the present invention is to apply an electromagnetic stirring device in a mold and reduce the slab at the final stage of solidification by light pressure reduction. A slab with reduced porosity (for example, 390 mm ×
480 mm) before hot rolling, using an existing forging press, for example, preforming to 300 mm × 420 mm to eliminate porosity at the center, that is, reheat to minimize heat energy loss. By hot rolling,
It is intended to produce round steel with a diameter of 150 mm or more from a large section stainless steel continuous cast material.

That is, the gist of the present invention is as follows.
In a method of manufacturing a round steel from a stainless steel continuous cast material having a large cross section, a stainless steel slab obtained by applying an electromagnetic stirring device in a mold and lightly reducing the slab at the end of solidification is used as a material, and has a diameter of 150 mm or more. In a forging process and a subsequent hot rolling process.

[0007]

The present invention will be specifically described below with reference to examples. FIG. 1 is a view showing a manufacturing process of a round bar having a diameter of 150 mm or more in the present invention. As shown in FIG. 1, a 390 mm × 48 porosity was reduced by applying an electromagnetic stirring device in a mold and reducing the porosity by slightly reducing the slab at the end of solidification.
A SUS316 slab of 0 mm is heated to a predetermined temperature in a heating furnace, and is heated to 300 mm by a two-column pull-down type hydraulic press.
After preforming to a size of 420 mm × 420 mm to eliminate the porosity at the center, that is, reheating to a diameter of 150 mm × 260 mm
Was hot rolled. The porosity in the center is diameter 2
30mm x 30mm x 30mm from rolled 10mm round steel
Were cut out, and the specific gravity was measured for a material with a forging process, a material without a forging process, and a portion near a distance of 1/4 of the diameter from the outer periphery.

FIG. 2 shows the result. As shown in FIG. 2, if the porosity is present, the specific gravity becomes smaller, but the specific gravity of the central portion of the material having the forging process is almost the same as the specific gravity in the vicinity of a distance of 1/4 of the diameter from the outer periphery, and the porosity disappears. The effect of the forging process is obtained. Further, when the entire length of the 210 mm-diameter round steel subjected to the forging process was subjected to ultrasonic inspection, there was no defect at the center.

[0009]

As described above, a stainless steel continuous cast material having a large cross section is preformed by the existing forging and hydraulic extension press, and the porosity of the central portion is press-bonded. The production of round steel with a diameter of 150 mm or more became possible, and a great effect was obtained for improvement of productivity, improvement of yield, and energy saving.

[Brief description of the drawings]

FIG. 1 is a view showing a manufacturing process of a round bar having a diameter of 150 mm or more in the present invention.

FIG. 2 is a diagram showing a specific gravity of a 210 mm-diameter round steel in the vicinity of the center and a comparative material according to the present invention.

FIG. 3 is a view showing a conventional manufacturing process of a round bar with a diameter of less than 150 mm.

FIG. 4 is a view showing a manufacturing process of a conventional round steel having a diameter of 150 to 260 mm.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI B22D 11/10 350 B22D 11/10 350A 11/128 350 11/128 350A

Claims (1)

[Claims] 1. A method for producing a round steel from a stainless steel continuous cast material having a large cross section, wherein a stainless steel slab obtained by applying an electromagnetic stirring device in a mold and lightly reducing a slab in a final stage of solidification is used as a material. A method of manufacturing a round steel using a large-section stainless steel slab as a raw material, wherein a round steel having a diameter of 150 mm or more is manufactured in a forging step and a subsequent hot rolling step.