JPS63295002A - Method for hot edging metal slab - Google Patents

Abstract

PURPOSE:To improve the product yield by edging a metal slab by a max. edging draft amount at the biting end and then edging with a drafting amount reduced by a drafting allowance amount and then edging the runout end part by a draft reduced by a drafting amount shown by a prescribed equation. CONSTITUTION:At edging a biting end 2 of a metal slab 1, edging with a max. drafting amount Hmax. is performed. A central part except the part 2 is edged by a drafting amount H found by subtracting a draft margin amount h from the max. drafting amount Hmax. Then, the drafting amount H is gradually reduced as an edging point approaches to the runout end and edging at the runout end part is performed by a drafting amount obtained by further subtracting a drafting amount shown by the equation I from the amount H. Thus, a crop loss is remarkably reduced because a width of the slab 1 after edging is held to be constant. Therefore, the product yield is improved.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a rolling method for rolling a metal slab in the width direction using a vertical rolling mill. The present invention relates to a rolling method for preventing the generation of irregularly shaped end portions.

(Prior art) The characteristics of the width reduction rolling method when manufacturing narrow width slabs from wide slabs are that, compared to conventional rolling, the ratio of the roll contact arc length to the average plate width during rolling, that is, the roll gap shape ratio. is 0.1~
The roll width is as small as 0.2, and the vertical roll width reduction amount per roll is as large as 200 to 300 mm. For this reason, irregularly shaped parts called fishtails occur at the front and rear ends of the rolled material, resulting in crop loss.

Many methods have been proposed in the past for reducing crop loss, which increases with width reduction. These methods apply the methods and knowledge that have been put into practical use in blooming. For example, a two-pass rolling method (4I !￥ Kosho 51-35383
(Japanese Patent Application Laid-Open No. 57-8190), a press forming method in which at least one longitudinal end of the material to be rolled is press-formed into a narrow width, and then rolled by a subsequent rolling mill (Japanese Patent Laid-Open No. 57-8190
Publication No. 2).

(Sounding or the problem to be solved) In either of these methods, the rolling efficiency is significantly reduced. In other words, the double-pass rolling method usually requires two rolling cycles to reduce the amount of reduction in one rolling process, and the press forming method requires stop time for positioning the rolled material and press operation process. is necessary. Therefore, these methods cannot be applied to a width-reducing vertical rolling mill, which was developed to realize a process that combines the continuous casting process and the rolling process, which can utilize the sensible heat possessed by the continuously cast slab. When manufacturing various slabs from wide to narrow slabs using the width rolling process, which directly connects the continuous casting process and the hot product rolling process, it is necessary to have rolling efficiency that matches the capacity of the preceding and following processes, so that it does not interfere with the rolling time. Therefore, it is required to reduce the crop loss at both ends of the rolled material.

The present invention provides an effective width reduction rolling method for metal slabs that solves the above problems.

(Means for solving problems) The gist of the present invention is as follows.

When performing reversible rolling of a metal slab in the width direction with a vertical rolling mill, a plurality of passes with the maximum width reduction amount of the rolling mill based on the target full width reduction amount of the metal slab and a single pass that is less than the maximum width reduction amount. When calculating passes, allocating the width reduction allowance of a single pass to a predetermined pass, and performing width reduction rolling of any pass of the predetermined passes to which the reduction allowance is distributed except for the final pass, the maximum width is calculated. Bite rolling is performed with the rolling foot, and after biting, the width rolling is changed to a width reduction amount that is obtained by subtracting the distributed width reduction margin, and after that, for biting, the end portion is reduced by the width reduction amount given by the following formula. A method for hot width rolling of a metal slab, characterized in that width rolling is performed by changing the amount of width reduction.

Yug = 0.3 □ (-) - (
Ig) D-roll diameter (mu) B: Applicable rolling pass width Slab before reduction [(■ff1) E: Reduction amount obtained by subtracting the distributed reduction allowance from the maximum reduction amount
(m11) (Function) Hereinafter, the function of the present invention will be explained with reference to the drawings. Figure 3 (a
), when the metal slab 1 is rolled in the width direction, irregularly shaped parts called fishtails are generated at the biting edges 2 and the biting edges 3. The mechanism by which this deformed portion occurs is that in one-width large reduction rolling, there are end deformations 2' and 3' caused by steady rolling as shown in FIG. 3(b), and end deformation 2 as shown in FIG. 3(C).

Therefore, the amount of fishtail at the biting end and the biting end of the metal slab is different, and as a result of investigation by the present inventors, as shown in Figure 4, the biting end and the biting end are different. It was found that the width of the irregularly shaped part 3 at the cutting end is approximately three times that of the irregularly shaped part 2 at the biting end.For this reason, by setting the width reduction of the biting end of the vertical rolling mill to be larger than that at the cutting end, the fish It was confirmed that tail eyelids can be significantly improved.

Figure 2 (a) is an example of the stand configuration of a width reduction rolling mill.
A horizontal roll 5 is disposed between two stands of vertical rolling mills 4 and 6. The metal slab is fed in the direction of the arrow a, reversibly rolled between stands 4, 5, and 6, and finished in the direction of the arrow. In this rolling process, the number of passes is calculated from the maximum rolling amount determined by the rolling load limit of the vertical rolling mill.
7 shown in FIG. 2(b). On the other hand, the number of passes in actual rolling is an integer number, as shown in the ti diagram of 8, and is an odd number of passes in the finishing direction. For this reason, a single pass less than the maximum reduction amount occurs compared to the number of passes, 7, calculated using the maximum reduction amount. That is, this single pass has a margin of reduction with respect to the maximum amount of reduction. In FIG. 2(b), a reduction margin of 9 is generated for the finished slab width Wc.

This rolling margin is distributed to each pass. Rolling allowance for each pass h1. Possible distribution methods include equal distribution, gradually decreasing slope distribution, gradually increasing slope distribution, etc.

No. 21'l (C) is the amount of rolling margin per vertical roll calculated by the equal distribution method for each width of the finished slab.

FIG. 1 shows the rolling method according to the present invention. As shown in FIG. 1(a), when rolling the engagement end 2 of the metal slab 1, rolling is performed with the maximum rolling reduction amount ΔHmax, and the central portion other than the engagement end is rolled as shown in FIG. 1(a).

As shown in (b), rolling is performed using a rolling reduction amount ΔH obtained by subtracting the allocated rolling allowance amount Δh from the maximum rolling reduction amount ΔHmax. In addition, when + @ punching is performed with constant ΔH at the edge 3, the width is reduced due to the metal flow effect in the unsteady part, and the bite is small due to the edge stripping reduction, and the effect of the strong reduction at the end of the bite in the next pass is also small. Therefore, in the unsteady rolling region, ΔH is gradually reduced as it approaches the end, and rolling is performed while controlling so that the width after rolling remains constant. As a result of investigation by the present inventors, it was found that the amount of width reduction due to the metal flow effect when rolling is carried out at a constant ΔH is given by the following equation.

However, Δg′: amount of width reduction due to metal flow effect
(ms) D: Roll diameter (mm) B: Applicable rolling pass width Slab width before reduction (■) ΔH: For biting, the width reduction amount at the end (IIll) Therefore, the vertical roll opening degree is widened by the amount of reduction in width. If the width of the slab is controlled in the direction of 1, the width of the slab after rolling can be made constant.

In the next pass in which the rolling direction is reversed, according to the method of the present invention, the biting is done by end die rolling and the biting is done by end stripping. Since this utilizes the margin of reduction relative to the maximum reduction needle, it can be carried out without interfering with rolling time, and crop loss can be significantly improved.

Therefore, the method of the present invention can be applied to a width reduction mill in a process that directly connects a continuous casting process and a hot rolling process, and can enjoy a great effect on yield improvement.

(Example) Next, an example of the method of the present invention will be shown. The rolling conditions are as shown in Table 1, and J! ! Continuous casting slab t280xw1800+a
m to finished slab dimension t250 Xw (700~+
800) m+s size was manufactured.

Table 2 shows the crop reduction rate by comparing the method of the present invention and the conventional method for various slab widths. For biting, reduce the width reduction amount at the end, D2 roll diameter, B: Slab width before rolling width, E: Maximum reduction amount by subtracting the distributed reduction margin amount from the maximum reduction amount. (reduction amount) was used.

Incidentally, the crop loss reduction rate is the improvement rate when the method of the present invention and the conventional method are employed compared to the case where rolling is performed with a constant reduction amount without changing the reduction amount.

As is clear from the examples in Table 2, the conventional method increases the number of passes and significantly lowers the rolling temperature, which increases the rolling load and makes it impossible to adjust the screw opening, resulting in cases where rolling is impossible. occured.

Table 2 Comparison with Conventional Method (Note) - indicates that rolling is impossible due to temperature drop. Figure 5 shows the rolling schedule according to the method of the present invention when rolling to the same finished slab width. continuous casting slab t
When producing finished slab dimensions t 250 x w 1155 mm from 280 x w 1800 mm, several rolling schedules can be set by the method of the invention.

Example 1 is a case in which the rolling margin is distributed evenly, Example 2 is a case in which the rolling margin is distributed so as to gradually decrease, and Example 3 is a case in which the rolling margin is distributed so as to be gradually increased. In either case, the crop amount was 4596 compared to the conventional method, showing a reduction rate of 55 tons.

(Effects of the Invention) It is impossible to apply the conventional method to a width reduction rolling mill in a process that directly connects a continuous casting process and a hot rolling process because it significantly impedes the rolling time. According to the method of the present invention, crop loss is improved without interfering with rolling time, making it possible to significantly improve yield, and bringing about industrially very useful effects.

[Brief explanation of the drawing]

Figure 1 (a) (b) is an explanatory diagram of the rolling method with biting end rolling and light rolling at the end. Figure 2 (a) (b) (c) is an illustration of the rolling method with two vertical rolling mills. Figure 3 (a) (b)
(C) is an explanatory diagram of the fishtail generation mechanism that occurs during width reduction rolling. Figure 4 is a diagram showing the relationship between the amount of fishtail at the end of bite and bite end and the amount of width reduction. Figure 5 is the same. It is a figure showing the rolling schedule by the method of the present invention when rolling to the finished slab width. 1... Metal slab, 2... Engagement end, 3... Engagement is the end.

Claims (1)

[Claims] When performing reversible rolling of a metal slab in the width direction with a vertical rolling mill, a plurality of passes in which the maximum width reduction amount of the rolling mill is set based on the target full width reduction amount of the metal slab, and the maximum width. Find a single pass that is less than the rolling reduction amount, distribute the width reduction allowance of the single pass to a predetermined pass, and execute width reduction rolling of any pass of the predetermined passes to which the reduction allowance is distributed, excluding the final pass. In doing so, bite rolling is performed with the maximum width reduction amount, and after biting, the width rolling is changed to a width reduction amount that is obtained by subtracting the allocated width reduction allowance, and then the bite-through end is given by the following formula. A method for hot width rolling of a metal slab, characterized in that width rolling is performed by changing the amount of width reduction to a reduced amount of width reduction. Δg=0.37(D/B)^-^0^. ^6^6E/2
However, Δg: Width reduction amount reduction at the end of bite (mm) D:
Roll diameter (mm) B: Applicable rolling pass width Slab width before rolling (mm) E: Reduction amount (mm) obtained by subtracting the distributed reduction allowance from the maximum reduction amount