JPH05200411A - Method for edging slab - Google Patents

Abstract

PURPOSE:To enable restraining breadthwise variation small at the tip and rear end in the rolling of the ensuing stage by edging a slab for widening the tip part and rear end part so as to provide plural stair-like stepped parts. CONSTITUTION:A slab 2 is successively fed between press tools and the slab width of the slab 2 is rolled down with the inclined part of the press tool. When the slab is passed between the tools by a prescribed length, a 1st stepped part 2a is formed by narrowing the rolling-down width to a width corresponding to a 2nd width widening amount. When the slab is further passed through the tools, the 2nd stepped part 2b is formed. While the rolling-down width is held in a normal width as it is, edging is continued. In this way, widened area having the stepped parts 2a, 2b of two steps is formed at the tip of the slab 2. The slab 2 is further fed between the tools, the 1st stepped part 2c on the side of the rear end part is formed and then, the 2nd stepped part 2d in the rear end part is formed by widening the rolling-down width by one corresponding to the 2nd width widening amount in the rear end part when the prescribed amount of the slab 2 is passed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slab width reduction method for changing the width of a slab to a predetermined width before rolling the slab in a hot rolling operation of the slab.

[0002]

2. Description of the Related Art It is generally practiced to press a slab after continuous casting into a predetermined width with a pressing tool before rolling. At this time, in the width reduction treatment, when the slab width is clamped so as to have the same width from the front end to the rear end, when rolling is performed, at the front end portion and the rear end portion of the slab, the rolled metal is Since it flows in the longitudinal direction and the width becomes insufficient, so-called crops grow very large.

As a method of avoiding this, a method of reducing the width shortage of the front end portion and the rear end portion of a steel sheet manufactured by rolling a slab whose width is reduced by a press tool and having its width changed to a predetermined width is conventionally known. There is known a slab width reduction method described in JP-A-63-140701. This is because when the slab is clamped with a pair of press tools, the front end and the rear end have a constant rolling width wider than the steady region, which corresponds to the difference in the width return amount between the end region and the steady region. There is disclosed a width reduction method in which a wide area having a constant width wider than the width of the stationary portion is formed at the front end portion and the rear end portion of the slab by performing a pressing process on the portion.

[0004]

However, in order to prevent the width of the front end portion and the rear end portion after rolling as described above, the width of the front end portion and the rear end portion is made constant and wider than that of the stationary portion. That is, by rolling in the next process, a wide-area metal corresponding to the width amount flows to the steady portion side, and a bump-shaped overwidth is generated at a place slightly entering from the leading end portion and the rear end portion to the steady portion. There is a problem that occurs.

Further, since the width change in the longitudinal direction of the front end portion and the rear end portion after rolling changes depending on the length of the slab and the width reduction amount, the width variation of the front end portion and the rear end portion after rolling (insufficient width,
It is difficult to select a press-molding pattern (amount of step and its length) of the wide portion that completely eliminates the overwidth. That is, increasing the step amount and the length of the wide portion to eliminate the width shortage increases the overwidth, and conversely, reducing the step amount and the length to eliminate the overwidth increases the width shortage. It is difficult to reduce the shortage and the excess at the same time.

The present invention has been made in view of the above problems, and preforms a slab into a width shape capable of simultaneously reducing the width shortage and overwidth of the front end portion and the rear end portion after rolling. The purpose is to reduce the width of the slab.

[0007]

In order to achieve the above-mentioned object, the slab width reduction method of the present invention is to press the slab across its width in the longitudinal direction before carrying out rolling treatment. In this case, in the width reduction method of reducing the width of the front end portion and the rear end portion of the slab so as to be wider than the width of the stationary portion, the width of each wide width to be given to the front end portion and the rear end portion, It is characterized in that a plurality of step portions are formed toward the stationary portion side, respectively, and the pressing width is controlled so as to be gradually reduced to perform the clamping processing.

That is, the opening degree of the press at the front end portion and the rear end portion is divided into several times along the longitudinal direction and sequentially changed so as to form a plurality of steps, thereby forming a multi-step wide width.

[0009]

The cross-sectional shape in the width direction of the slab after width reduction is usually a so-called dogbone shape in which the thickness of the width direction end portion is thicker in the steady portion than in the front end portion and the rear end portion.
The width return when rolled is larger than that at the front end and the rear end. For this reason, if the width of the steady portion and the front end portion and the rear end portion are preformed to the same width by the width reduction before rolling, the front end portion and the rear end portion will be insufficient in width. Therefore, the width return amounts of the front end portion and the rear end portion and the stationary portion are predicted, and the front end portion and the rear end portion are subjected to pinching processing so as to be wider than the stationary portion accordingly.

Further, when rolling is performed on the preformed slab, the metal moves in the longitudinal direction and the width direction, but the stationary part where the metal is hard to move in the longitudinal direction is smaller than the leading end part and the trailing end part. And the metal at the front end and the rear end easily flows in the longitudinal direction as compared with the stationary part. For this reason, if the front end and the rear end are pre-formed to be wide in order to reduce the width shortage after the rolling of the front end and the rear end, a part of the metal in the wide width moves to the steady portion side and the wide width is increased. In the present invention, a bump-like overwidth is generated in the steady portion close to the constant portion. However, in the present invention, the wide width amount in the wide area is changed in a stepwise manner to reduce the wide width amount in the wide portion close to the steady portion. The metal movement from the wide area that contributes to the overwidth is reduced to reduce the occurrence of overwidth, and by increasing the width on the end side, the width shortage at the end is reduced.

The reason why the width of the wide area is changed stepwise is that the pressing work by the press tool can be controlled easily.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 2, a slab 2 is passed between a pair of press tools 1 whose pressure lower surfaces 1a are opposed to each other on the left and right to have a predetermined width. Be suppressed. Slab 2 pre-formed by width reduction
Is rolled into a predetermined steel sheet by a plurality of rolling mills 3 in the hot rolling process.

The width reduction of the slab 2 by the press tool 1 is as shown in FIG. 3 (a). First, as shown in FIG.
The slab 2 is sequentially fed between the press tools 1 by controlling so as to have a wide amount D1 of the press tool 1, the width of the slab 2 is gradually reduced by the inclined portion 1b of the press tool 1, and the pressing surface 1a causes the tip to reach the above-mentioned reduction width. The slab width of the part is reduced.

When the width-reduced slab 2 passes between the press tools 1 by a predetermined length, the reduction width of the press tool 1 is secondly narrowed as shown in FIG. 3 (b) until the width D2 is met. To form the first step 2a. Further, the second
When the wide portion of the press tool 1 passes through the press tool 1, as shown in FIG. 3C, the reduction width of the press tool 1 is narrowed to an amount commensurate with the width D4 of the steady part to perform the width reduction of the steady part. Step 2
b is formed. As shown in FIG. 3D, the width reduction is continued while keeping the reduction width at the steady width D4.

As a result, a wide width region is formed in which the front end portion of the slab 2 has two step portions 2a and 2b. further,
When the slab 2 is fed between the press tools 1 and the wide portion of the rear end portion of the slab 2 enters between the press tools 1, as shown in FIG. 4 (a), the reduction width between the press tools 1 is set to the rear end. The first step portion 2c on the rear end side is widened in accordance with the first wide amount D5 of the portion.
Is formed, and when the slab 2 has passed a predetermined amount, the state shown in FIG.
As shown in (3), the reduction width is widened by an amount corresponding to the second wide amount D6 of the rear end portion to form the second step portion 2d of the rear end portion.

As it is, the rear end of the slab 2 is shown in FIG. 4 (c).
By passing between the press tools 1 as shown in FIG. 3, a wide width area having two step portions 2c and 2d is formed at the rear end portion of the slab 2. The width amounts D1 to D5 are determined in advance from the width return amounts of the stationary portion and the tip portion obtained by a known method.

By the width reduction of the slab 2, the slab 2 is preformed into a shape as shown in FIG. The widthwise cross-sectional shape of the front end portion, the stationary portion, and the rear end portion of the slab 2 after the width reduction is as shown in FIG. 5, and compared with the front end portion and the rear end portion, the dog bone of the stationary portion is You can see that the height is high. As a result, the width reversion after rolling becomes larger in the stationary portion than in the leading end portion and the trailing end portion, but in this example, the leading end portion and the trailing end portion were formed wider than the steady portion, The shortage of width that occurs later at the front end and the rear end is reduced.

Further, due to the movement of the leading end portion and the trailing end portion in the longitudinal direction, particularly toward the steady portion side, a bump-like overwidth occurs in the steady portion close to the wide portion. Since the amount of widening on the stationary portion side, which contributes the most to the width, is suppressed to a small amount, the movement of the metal by rolling becomes smaller than in the conventional case, and the occurrence of the bump-shaped overwidth is reduced. This is shown in the figure. In the case where the wide width of the front end and the rear end was preformed by the conventional width reduction method to have one step as shown in FIG. 6, it was rolled. The width side of the front end portion and the rear end portion of the formed steel sheet has a shape as shown in FIG. 7. However, as in this embodiment, the wide side has a two-step portion as shown in FIG. In the case of preforming, the width side of the front end portion and the rear end portion after rolling has a shape as shown in FIG. 8, and overwidth B and width shortage A are reduced as compared with the conventional width reduction method. I understand. It should be noted that in FIGS. 7 and 8, the dotted line shows a width shortage that occurs when a wide width region is not formed during width reduction.

With respect to the above, for a slab having a slab width of 1600 mm, the above wide area is preformed by one step as in the prior art, and two steps are provided as in this embodiment. Compare both slabs that have been preformed. Here, the width-killing amount of each slab was 265 mm and 272 mm, respectively. When the slabs preformed as described above were examined for the shape in the width direction after being rolled by the first rolling mill in the rough rolling step, the results shown in FIG. 9 were obtained. 9A shows a slab preformed by the conventional width reduction method, and FIG. 9B shows a slab preformed by the width reduction method according to the present invention. However, the middle part of the steady region is omitted in the figure. Comparing the width shortage A at the tip end based on this figure, the width shortage of only 50 mm has occurred in the past, but in this embodiment, 2
It can be seen that the width is 3 mm and it is small.

In the above embodiment, only two steps are formed, but the pressing width may be controlled by the press tool 1 so that three steps or more are formed.

[0021]

As described above, the slab width reduction method of the present invention is performed by performing the width reduction in which the front end portion and the rear end portion are widened by a plurality of stepped steps, and It is possible to obtain an effect that the width variation (insufficient width / overwidth) of the leading end and the trailing end during rolling in the process can be suppressed.

[Brief description of drawings]

FIG. 1 is a plan view of a slab preformed by a width reduction method according to an embodiment of the present invention.

FIG. 2 is a schematic process drawing for a slab of an example according to the present invention.

FIG. 3 is a first schematic process drawing of width reduction of the slab of the example according to the present invention.

FIG. 4 is a second schematic process drawing of width reduction of the slab of the example according to the present invention.

FIG. 5 is a view showing a cross-sectional shape in the width direction of the slab after the width reduction treatment.

FIG. 6 is a plan view of a slab preformed by a conventional width reduction method.

FIG. 7 is a diagram showing a width variation after rolling of a slab preformed by a conventional width reduction method.

FIG. 8 is a diagram showing a width variation after rolling of a slab preformed by the width reduction method of the example according to the present invention.

FIG. 9 is a diagram showing a width variation of the slab on the delivery side of the first rough rolling mill.

[Explanation of reference numerals] 1 press tool 2 slabs 2a, 2b, 2c, 2d step section 3 rolling mill

Claims (1)

[Claims] 1. When the slab is subjected to clamping processing over the width direction in the longitudinal direction before the rolling process is performed, the width of the front end and the rear end of the slab is made wider than the width of the steady part. In the width reduction method in which the width is reduced so that the width of each of the wide widths given to the front end portion and the rear end portion is gradually reduced while forming a plurality of step portions toward the steady portion side, respectively. A method for reducing the width of a slab, which is characterized by controlling the pressure.