JPS58135703A - Preforming method of slab - Google Patents

Abstract

PURPOSE:To decrease the fish tail produced by hot rolling and to improve yield by forming compression formed parts in the transverse direction in the top or rear end part of a slab with a vertical scale breaker thereby preforming the slab inexpensively. CONSTITUTION:At least one of the top and rear ends of a slab S heated in a heating furnace 1 are pressed to form compression-formed parts Sc on both end parts of the slab just before edging with the vertical rolls 21 of a vertical scale breaker 2 prior to edging with said rolls and further prior to hot rolling with the edger rolls 31 and horizontal roughing rolls 32 of roughing mills 3. If the slab S preformed in such a way is subjected to ordinary broadside rolling with the vertical rolls 21, the top and rear end parts of the slab S pass through the rolls without rolling down; therefore, the growth of fish tails is small and the fish tails after the rolling is decreased condiderably.

Description

[Detailed description of the invention] The present invention relates to a slab preforming method.

Generally, during hot rolling of slabs manufactured by continuous casting or blooming, the so-called width cutting is performed to ensure the width of the finished product, resulting in fish formation at the leading and trailing ends of the strip 10, as shown in FIG. Tail F is formed.

In addition, recently, the number of molds has been reduced in order to simplify continuous casting, so it may be necessary to perform the aforementioned width reduction forcefully, and Fish Tail F tends to become more and more doglike. There is. Since this fish tail F is discarded after rolling, it is the biggest cause of yield decline.

As a method for reducing fish tails, a method has been proposed in which a slab end preforming device is installed on the entry side of a rough rolling mill, and the slab end is preformed prior to hot strip rolling. However, this method requires a new preforming device to be installed on the rough rolling line. Installing a new preforming device is expensive, and there are also problems in securing installation space.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to utilize existing techniques to preform a slab into a predetermined shape, reduce fish tails that occur during hot rolling, and improve yield.

The slab preforming method of the present invention uses vertical rolls of a vertical scale breaker installed on the entry side of a rough rolling mill to reduce the tip end of the slab to zero. The present invention is characterized in that a compression molded portion is formed in the width direction on at least one of the rear end portions prior to hot rolling.

Hereinafter, the method of the present invention will be explained based on the drawings.

In normal hot rolling, as shown in Fig. 2, the slab S heated to a predetermined temperature in the heating furnace 1 is rolled over the entire length of the slab S by the vertical rolls 21 of the vertical scale breaker 2 of the rough rolling line. After carrying out the usual width reduction, it is continued to be hot rolled by the edge roll 3j of the rough rolling mill 3 and the horizontal rough rolling roll 32.

In the present invention, as shown in FIG. 3, prior to the hot rolling, the front end or rear end of the slab S is One (Fig. 4 (A)) or both (Fig. 4 (A))
Figure (B)) is pressed to form compression molded parts S on both edges of the slab.
form c.

As shown in FIG. 5, the compression molding part Sc has a predetermined length from the end surface S+ of the slab S, and is attached to the vertical roll 21 of the vertical scale breaker 2 at a predetermined depth E at both edges in the width direction. It is formed into a circular arc shape whose radius is the radius of curvature.

The length L and depth E of the compression molded portion are appropriately determined based on conditions such as slab dimensions, product dimensions, and rolling schedule.

When the compression molded part Sc is formed on the slab S by the vertical rolls 21, the end surface S1 of the slab S is actually moved inward in the widthwise direction by a depth B due to the flow of the material, as shown in FIG. curve.

However, if the preformed slab is vertically
When normal width reduction rolling is performed over the entire length by the vertical rolls 21 of the scale breaker 2, the front and rear ends of the slab pass through without being rolled down, so there is less fish tail growth and the line sea tail after rolling is reduced. decreases significantly.

Next, specific examples of the method of the present invention will be described.

(1) Dimensions of slab used 41: Thickness 250+a+X width 1200m'x length 5
00011111&2: Thickness '25 QswX+l@
145 QmX, J4 length 5000m + (2) Compression molding part dimension L = 200 + m Vertical roll diameter D = 1100mE
= 357 + 111 (3) Rough rolling width reduction amount (= slab width - rough rolling width) = 80 + + o + + thickness after rough rolling - 30 constant (4) Rough rolling results Results of comparison between the method of the present invention and the conventional method without preforming are shown in Table 1 below.

According to the method of the present invention, since slab preforming is performed using existing equipment, there is no need to install a new preforming device in the hot rolling line, and the front and rear ends of the strip after hot rolling are It is possible to significantly reduce fish tails and improve yield.

[Brief explanation of drawings]

FIG. 1 is a plan view of a strike IJ tube rolled by a conventional method. FIG. 2 is a schematic plan view of a rough rolling facility to which the method of the present invention is applied. FIG. 3 is an explanatory diagram showing the method of the present invention. FIG. 4 is a plan view of a slab preformed by the method of the present invention. FIG. 5 is an explanatory diagram showing the method of the present invention. 1: Heating furnace 2: Vertical scale breaker 3: Rough rolling mill 21: Vertical roll 31z Edge roll 32; Horizontal rough rolling roll S: S 7
p = fish tail L:
Length E: Depth Patent applicant Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] Using the vertical rolls of a vertical scale breaker installed on the entry side of the rough rolling mill, compression molding is performed in the width direction on at least one of the leading and trailing ends of the slab prior to hot rolling. A method for preforming a slab, characterized by forming the slab by two steps.