JPS6268601A - Hot cross rolling method for metallic slab - Google Patents

Abstract

PURPOSE:To subject a slab to hot cross rolling to good quality by rolling both side parts of the slab to a finish target thickness by horizontal rolls having recessed crowns at the width center, then reiterating the rolling by vertical rolls and the above-mentioned horizontal rolls to a prescribed width and rolling the slab to the target thickness by the horizontal rolls. CONSTITUTION:Both side parts of the slab are rolled to the target finish thickness hn by the horizontal rolls having the recessed crowns in the width center part in the case of rolling the metallic slab having the thickness h0 and width w0 by the hot rolling using the horizontal rolls and vertical rolls with calibers to the target thickness hn and width wn. The slab is rolled to the width w1 by the next vertical rolls to forma locally increased thickness part 5 to h0+h<+> and a peak sections 7 of the locally increased thickness part are rolled to the thickness h0 by the above-mentioned horizontal rolls. The width center thickness hn+DELTAh2 is made smaller than the initial hn+DELTAh0. The slab is rolled to the hot cross rolled material of the target thickness hn and width wn having good quality with less tensile stress in the central part and without having recesses if the slab is rolled to the prescribed width by the reiteration of the rolling by the vertical and horizontal rolls and is rolled by the horizontal rolls.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a hot width rolling method for rolling a metal slab using a vertical roll with a force IJ/2 and a horizontal roll.

(Prior technology) Size consolidation of the width of metal slabs has been attempted with the aim of realizing a process that directly connects the continuous casting process, which can effectively utilize the sensible heat retained by continuous casting slabs, and the rolling process, which creates the product shape. . Therefore, in order to create the slab width necessary for the rolling process, a large width reduction is performed downstream of the continuous casting equipment.

This rolling of the metal slab in the width direction is carried out using the so-called force IJ having a groove shape.
This is done in a vertical rolling mill equipped with vertical rolls, but if the width change t is increased by increasing the widthwise reduction, the slab cross section will have a locally increased thickness called a dogzine. Occur. As a hot width reduction rolling method for this purpose, for example, as disclosed in JP-A No. 55-117501, the whole of the locally increased part of the plate thickness caused by width rolling is reduced by horizontal rolls, and before the width rolling, A metal slab width rolling method in which the metal slab is returned to the same thickness as the original metal slab thickness, and width rolling is repeated again using a vertical roll with a caliber, and
The continuous cast slab presented in Publication No. 55842 is initially rolled down in the thickness direction with a reduction amount distribution in the width direction so that the amount of reduction at the center of the slab width is smaller than the amount of reduction at the ends of the slab. There is a width reduction rolling method in which the sheet is then rolled down in the width direction and then rolled down in the thickness direction to make the sheet thickness uniform.

(Problem to be Solved by the Invention) As proposed in the former prior art, the locally increased thickness at both ends of the plate, which occurs due to wide reduction rolling, is horizontally rolled to the original thickness of the metal slab. When so-called dogzane level rolling is carried out, when the thickened parts at both ends of the plate are stretched in the longitudinal direction, the central part in the width direction is also stretched in the longitudinal direction, resulting in a depression in the central part of the width. Compressive stress due to rolling does not act on this depression, it is just a tensile phenomenon, and the material is inferior in quality without being subjected to plastic working due to rolling, and surface flaws often occur.

In addition, if a rolling method is carried out in which rolling is performed in the thickness direction with a distribution of the reduction in the width direction so that the reduction in the central part of the slab width is smaller than the reduction in the ends of the slab width, as in the latter prior art, In the process of the next large slab width reduction, the above-mentioned depression at the center of the width is further promoted.

The problems of the above conventional technology will be explained with reference to the drawings.

FIG. 2 (al) shows an example of the stand configuration of the width reduction rolling mill V1. .3.4 is reversibly rolled. Figure 2 (bl
, (c) and Id) illustrate the cross-sectional shape of the slab during the rolling process. That is, the base width W shown in FIG. 2(b). 9 yuan thick. When a continuously cast slab having a rectangular cross-sectional shape is rolled with a reduction amount △W1 in the width direction as shown in FIG. A locally increased thickness portion (so-called doggain) 5 occurs at the end.

If this locally increased thickness portion 5 becomes large, it will cause surface flaws due to biting out of the holes of the vertical roll with carina and an increase in the rolling power for rolling in the width direction. These factors restrict the amount of width rolling that can be rolled, so as shown in Fig. 2(d), the locally increased thickness is horizontally rolled down using the horizontal rolls 3, and the thickness ho+h6 is the same as the original thickness. the law of nature. The rolling process shown in FIGS. 2(c) and 2(d) is then repeated in such a manner that width rolling in the width direction of the strip is again carried out using a vertical roll with carino-rolls to reduce the strip width. In this case, Figure 2 (
As shown in d), the metal slab has a depression in the center of the width of the plate due to the phenomenon of thinning, and the center of the width of the plate has a cross-sectional shape that is h-thinner than the ends of the width of the plate. After the width rolling is completed, the material is rolled to the target thickness using horizontal rolls as shown in FIG. 2(e). As a result, the central part of the metal slab has a target thickness hnJ:,6
A slight warmth develops. This recessed portion is never rolled down during the rolling process, resulting in inferior material, and quality defects are concentrated in this portion.

For this reason, in the width rolling process, which has conventionally been directly connected to the continuous casting process, it is necessary to improve the material quality of the center part during width rolling without impairing rolling efficiency. A hot width rolling method for slabs has been strongly desired.

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

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention aims to solve the above-mentioned problems by providing horizontal Using a horizontal roll with a concave crown formed at the center of the roll width, both sides of the slab width are rolled to a target thickness, and the center of the slab width is rolled to a thickness greater than the thickness of both sides using the concave crown. The metal slab is rolled in the 9 width directions with rolls, and then the locally increased thickness caused by the width direction rolling is rolled with horizontal rolls to reduce the thickness of the metal slab before the horizontal roll rolling (hereinafter referred to as original thickness).
A method for hot width rolling of a metal slab, characterized by rolling the slab to a desired finishing thickness by repeatedly rolling it with vertical rolls and horizontal rolls to obtain a target finished width dimension, and then rolling it to a target finished thickness dimension with horizontal rolls. is the means.

(Function) In contrast to the width rolling method according to the prior art described above, the present inventor proposed a method for rolling metal slabs at the center of the width of the metal slab under the configuration of the vertical roll 2° 4 with a caliber and the horizontal roll 3 shown in FIG. 2(a). A horizontal roll with a concave crown in the center where the part is rolled is used to distribute the reduction amount in the width direction of the slab so that the reduction amount at the center of the slab width is υ smaller than the reduction amount at the ends of the slab width. After rolling the metal slab until the thickness on both sides of the width reaches the target finished thickness, the locally increased thickness caused by rolling in the width direction is rolled with horizontal rolls to the original thickness, and by repeating this process, the target thickness is achieved. After obtaining the width of the metal slab, it is rolled again to the target original size using horizontal rolls to obtain a predetermined shape.The continuous casting slab width is 1800a++.
, slab width 750~18 from a pair size of thickness 280fi
As a result of rolling various slab width sizes of 00 m and thickness of 250 m, the following findings were obtained.

That is, before rolling in the width direction, by rolling the slab in the thickness direction using the horizontal rolls with a distribution of the reduction amount in the width direction so that the amount of reduction in the central part of the slab width is smaller than the amount of reduction in both sides of the slab width, It is possible to obtain a cross-sectional shape in which the central part of the slab width is thicker than both sides of the slab width, and it is possible to prevent depressions in the central part that occur during the dogzine leveling rolling of subsequent width reduction rolling, and after rolling to the target thickness with horizontal rolls. Because the entire width direction is rolled, the entire width direction undergoes plastic processing by rolling, and the tensile phenomenon in the width reduction process is alleviated by making the central part of the slab width thicker than both sides of the width, resulting in quality defects. However, due to the formation of local thickened parts due to width rolling, metal is added to the side walls of the vertical rolls. In subsequent rolling, the locally increased thickness of the plate is rolled to the original thickness, so the bottom of the carino, which has the same dimensions as the original thickness, is always filled with metal and stable rolling can be performed. etc.

FIG. 3(a) shows the relationship between the depth of the depression generated in the central part of the slab width due to width rolling and the total width reduction amount to obtain the target slab width finished by width rolling from the continuous casting slab width. The cross-sectional shape in which the thickness of the slab is thicker in the center of the slab width compared to both sides of the slab width does not cause the phenomenon of flesh prickling in the center of the width, compared to the conventional case where dogzane leveling is carried out every time the width is rolled without consideration of this. As a result, the depression 1 at the center of the width is significantly improved. FIG. 3(b) shows an investigation of quality defects in the method of the present invention and the conventional method. As you can see from the figure,
In the method of the present invention, rolling is performed in the width direction after rolling to the target thickness using horizontal rolls, so quality defects are significantly improved not only at the center of the width but also at both sides of the width.

Based on these findings, the inventor of the present invention has determined that, under the structure of the vertical rolls 2 and 4 with calibers and the horizontal roll 3 shown in FIG. As shown in Figure 1 (a), finish the metal slab 1 on both sides of the slab width with the target thickness h and the width center part as hn+xhO(Δ
ha > 0), rolling is performed in the width direction as shown in Fig. 1 (bl), and the locally increased thickness portion 5 generated by the width reduction amount △W1 is rolled horizontally as shown in Fig. 1 (c). roll 3
The metal slab is rolled in the thickness direction to the original thickness ho, and the final target thickness is obtained.

The increased thickness part between and the original thickness hO is left in place in order to fill the bottom layer with a force IJ/~ to perform stable rolling, and a horizontal reduction is applied to the peak part 7 of the locally increased part of the plate 4, and thereafter, By repeating the rolling process shown in Fig. 1(b) and (C), the width is changed to the target strip width, and then the hot width rolling method is performed, in which the strip is rolled again to the target thickness t using horizontal rolls. completed.

In addition, the behavior of the width center part of the slab due to the tensile phenomenon in the main rolling process is such that each time the peak part of the locally increased part of plate 4 is rolled, the width center part hn+Δh2 shown in FIG. 1(C) changes from the initial thickness. , smaller than n + Δho (Δha〉△h2n,
At the stage of obtaining the target plate width Wn shown in Fig. 1(d), the initial reduction amount distribution is eliminated, and the finished target thickness h is
It is possible to obtain n, and the depression in the center width area □ is significantly improved.

(Example) Next, an example of the method of the present invention is shown.The rolling conditions are as shown in Table 1, and a continuous cast slab with a width of 1800 m and a thickness of 280
A target slab size width of 860 saa was manufactured from m.

Table 1 Rolling conditions The conventional rolling method carried out at the same time as a comparative example is as shown in Table 2 (,) as shown in the rolling schedule of JP-A-55-11750.
Rolling was performed as described in Publication No. 1.

On the other hand, in the embodiment of the present invention, as shown in the rolling schedule in Table 2 (b), after rolling to the target thickness with horizontal rolls, the local thickened portions generated by rolling in the width direction are removed by horizontal reduction rolling. After rolling to the original thickness, rolling was repeated again in the width direction using grooved rolls to obtain the target width, and then rolling to the target thickness.

Table 2 The results of both rolling schedules are shown in Table 3. As is clear from the comparison between the comparative example and the example in Table 3, the surface flaws of the slab are significantly improved, and the depression at the center of the width is also significantly reduced.

Table 3 Comparison of Comparative Examples and Examples (Effects of the Invention) In the conventional rolling method for widthwise rolling of metal slabs in a process that directly connects the continuous casting process and hot rolling process, the depression in the width center part Although the method is large and has many quality defects, the method of the present invention can improve the quality and quality of the metal slab without extending the rolling time, and brings about a very beneficial effect industrially.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing changes in the cross section of a slab in the width direction during the width rolling process according to the method of the present invention. FIG. , Fig. 2(b),(c),(a
1 is an explanatory diagram showing the change in the widthwise cross section of the slab during the width rolling process according to the conventional method. Figure 3 (a) shows the depth of the depression generated at the center of the width of the slab due to width rolling from the continuous casting slab width. A graph illustrating the relationship with the total width reduction amount to obtain the finished target slab width,
FIG. 3(b) is a graph illustrating the state of surface flaws when the conventional method and the method of the present invention are implemented. DESCRIPTION OF SYMBOLS 1...Metal slab, 2...Vertical roll, 3...Horizontal roll, 4...Vertical roll, 5...Local board thickness increase part, 6... Board width central part depression, 7...Local plate 4 augmentation apex site. Agent Patent attorney Masamitsu Akizawa and 2 others Figure 1 Figure 71'3 <a> Total width reduction amount (b ん ま ど - り) Method of writing procedural amendments based on directives) January 31, 1985

Claims (1)

[Claims] (1) When hot-rolling a metal slab to the target finishing thickness and width using a horizontal roll and a vertical roll with a caliber, the horizontal roll with a concave crown formed in the center of the width of the horizontal roll rolls both sides of the slab width to the finishing target thickness. First, the central part of the slab width is rolled by the concave crown part to a thickness greater than the thickness of the both sides, and then rolled in the width direction by the vertical rolls, and then the local plates generated by the rolling in the width direction are rolled. The increased thickness part is rolled with horizontal rolls to the thickness of the metal slab before horizontal roll rolling, and this rolling with the vertical rolls and horizontal rolls is repeated to obtain the target finished width dimension, and then the target finished thickness dimension is obtained with the horizontal rolls. A method for hot width rolling of a metal slab, which is characterized by rolling a metal slab to a maximum width.