JPS6316803A - Production of steel plate having excellent end quality - Google Patents

Abstract

PURPOSE:To prevent the generation of seam flaws at the four peripheral corners of a section by subjecting a stock to be rolled to chamber rolling. CONSTITUTION:At least one pass of the chamber rolling at the corners of the stock S to be rolled is executed before or after or before and after pass in the stage when the end shape of the stock S changes from double bulgings to single bulging. The inflection point to be generated at the point right under the rolls at the slab end face is thereby eliminated, by which the generation of the seam flaws is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to the production of cut plates or selvedge steel plates, and in particular, to prevent seam flaws from occurring at the corners of the four circumferences of the cross section.
The present invention relates to a method of manufacturing a steel plate.

(Prior Art) When conventionally manufacturing thick plates, vertical cracks called seam flaws or side cracks tend to occur on the front and back sides near the ridge lines in the longitudinal direction of the steel plate. Various methods have been proposed to prevent the occurrence of vertical cracks.

For example, Japanese Patent Publication No. Sho 41-16928 discloses a method in which a corner cutting is performed on an end of an ingot in the planar direction in order to ensure the prevention of flaws during the production of high-grade steel. Further, Japanese Patent Publication No. 59-39202 proposes a method of rounding the corners of a thick plate slab with a radius of curvature of 20 to 80. On the other hand, Unexamined Japanese Patent Publication No. 5
Publication No. 6-19908 discloses a method in which light reduction rolling is performed at the beginning of shape adjustment or tentering rolling of a slab in order to prevent the occurrence of defects when manufacturing lid steel. Furthermore, in the method disclosed in Japanese Patent Publication No. 50-14632, the center of both end faces of the slab is attenuated by convex caliper rolls to give a training effect and to prevent low occurrence.

The present inventor also discovered that during either or both of the sizing of the material to be rolled or the shape adjustment rolling before tentering rolling,
By forming a forged layer on the end surface of the rolled material,
We have developed a method for manufacturing steel plates with excellent end surface quality, and have filed an application for this method as Japanese Patent Application No. 113753/1983. Furthermore, Japanese Patent Application No. 61-67552 proposes and discusses a new method for achieving the above effect by performing etching during finish rolling.

[Problems to be Solved by the Invention] The corner cutting method proposed in Japanese Patent Publication No. 41-16928 exhibits an extremely reliable effect in preventing the occurrence of seam flaws. However, the corner cutting method has the disadvantage that it is inferior in terms of workability and yield, is not suitable for mass-produced steel, and is limited in its application to specific high-grade steels.

On the other hand, the light reduction rolling method F, t proposed in JP-A-56-19908 reduces the productivity of rolling, and its effect is not reliable.

In addition, in the rolling method proposed in Japanese Patent Publication No. 50-14632 and using convex caliper rolls, the depressions in the center of both sides of the slab absorb the width expansion of the steel plate that occurs during rolling, and prevent seam defects. Affects the location of occurrence. the result,
The location where flaws occur is limited only to the vicinity of the ridge line along the longitudinal direction of the steel plate, and this is the area where the flaws occur in the area that is cut off when cutting the ends, so an indirect effect can be obtained. However, it is not possible to prevent seam flaws from occurring, and even if the shape of the steel machine is improved, the edges must be cut off.

In contrast, Special Publication No. 59-39202, Special Patent Application No. 60-
According to the method proposed in Japanese Patent Application No. 113753 and Japanese Patent Application No. 61-67552, the occurrence of seam defects at the edges of steel sheets has been effectively reduced. However, the above-mentioned rolling method still has the drawback that it causes a reduction in yield due to slab force 1] or an increase in the amount of heat required in slab processing and edging rolling, resulting in increased energy consumption and equipment costs.

c) Means for Solving the Problems) In order to solve the above problems, the inventors of the present invention,
The occurrence of seam flaws on the end faces of rolled materials was investigated through repeated experiments and discussions. the result,
It has been found that seam defects are closely related to specific passes in horizontal rolling, that is, to changes in the end face shape of the rolled material as horizontal rolling progresses.

The present invention has been completed based on this knowledge, and consists of arranging at least one pair of horizontal rolls and one pair of vertical rolls to perform shape adjustment rolling, widening rolling, and finish rolling of a material to be rolled, thereby producing a steel plate. In the final rolling of the rolled material, at least one pass of the rolled material is carried out before or after the horizontal A where the end face shape of the rolled material bulges due to medium corrugations, or at least one pass before and after the rolled material. It is characterized by performing corner chamfer rolling, and at least 1 slot of rolling is performed before or after the horizontal pass where the shape ratio α becomes 1.0 or more for the first time, or before and after each of the horizontal passes. (Operation) The operation of the means of the present invention for eliminating seam flaws in a steel plate will be explained in detail.

As shown in Fig. 1 A, B, and C, seam flaws occur during horizontal finish rolling in thick plate rolling, and as the horizontal rolling of the material to be rolled progresses, the top and bottom of the cross section and ridge lines protrude (Stage A).
, occurs when the horizontal rolling of the nail progresses and reaches a roughly constant rolling reduction rate (stage B). The starting point occurs near the upper and lower ridge lines of the cross section of the material to be rolled, and the subsequent pull 1! As the width expands due to the subsequent horizontal reduction (stage C), the side surfaces of the material to be rolled turn around to the front and back sides, and due to such plastic flow of the material,
The position of the seam flaw is 10 to 10 minutes from the widthwise end of the rolled material.
The present inventors discovered that it moves to the center side of the front and back sides located on the inside of 5'Oa+.

Moreover, the shape of the end face of the rolled material is widened, making it easier to repulse.
When zinc is applied, the shape of the end face of the material to be rolled changes from stage A, where the knurled portions a are located at two locations above and below along the sides of the material to be rolled, to stage B, where the knurled portions a are located at one location in the center. It was discovered that this seam flaw occurs when one horizontal rolling pass is performed after the process. The end face shape of this rolled material changes from a double bulge (stage A) to a single bulge (stage B) when the rolling shape ratio α becomes 1.0 or more, as shown in Figure 2. I found that it was during the compression pass.

Here, the rolled shape ratio α is defined by equation (1).

1/2 (H1+H2) However, R: Horizontal roll radius Hl: Entry side plate thickness during horizontal reduction H2: Output side plate thickness during horizontal reduction △H: Amount of retainer that can be tied horizontally (ΔH = H4-1 (2) ) In other words, as a result of repeated experimental studies to eliminate the occurrence of seam defects, we found that at the stage where the end face shape of the rolled material changes from a double bulge (stage A) to a single bulge (stage B), we Alternatively, it has been found that a more effective means for achieving the objective is to chamfer the corner part of the rolled material of at least one groove at each of the front and rear. By doing this, the width expands to bulge, that is, double bulge (
During the change from stage A) to single ball) (stage B), the inflection point that occurs directly below the roll on the end face of the slab is eliminated, and as a result, seam flaws are no longer generated.

FIGS. 3A and 3B are schematic side sectional views showing an example of a face-wall bending device. Fig. 3 (al is the edge roll 1 with a force of 11, S is the material to be rolled, σ is the cutting angle, 2 is the chamfered violet -f6, and Fig. 3 al is the inclined roll 3, 4 Hydraulic cylinder for pressing the tilted roll, R is a curved surface.In place of this tilted roll 3VC, a hot grinder (not shown) may be used, but from the viewpoint of material yield, forming a roll is preferable. .The above chamfered gong 3 is
It is sufficient that the end face of the rolled material S fixed to the horizontal rolls has an inflection point of 3 to 15 am, which eliminates the inflection point formed by bulging due to width expansion.

('#Example) Hereinafter, the present invention will be described in detail with reference to comparative examples and comparisons.

Table 1 shows rolling conditions and rolling results accordingly. In these examples, we set the slab size to 240
The conditions were set: amX1800+n+nX5000+o+, and the tenting start thickness was 200+a.

As is clear from Table 1 and FIG. 1, when the manufacturing method according to the present invention was used, the occurrence of seam defects was prevented, and the repair rate and rejection rate were significantly reduced. As a result, the yield was significantly improved.

(Effects of the Invention) As explained above, in the present invention, corner chamfering is performed before and after the finishing groove where the end shape of the rolled material changes from a double bulge to a single noserge. By doing so, the occurrence of seam flaws is significantly reduced,
Virtually none.

As a result, the yield in manufacturing thick plates is improved and the incidence of maintenance is reduced. In addition, when manufacturing all steel plates where the shape of the end face is a problem, such as grooved steel plates, rest trim steel plates, or no trim steel plates, the end face quality of the steel plate can be guaranteed, so the processing process is controlled from the steel plate manufacturing authority. Significant improvements in yield and quality can be achieved over time.

[Brief explanation of the drawing]

Fig. 1 is a drawing showing the relationship between the mechanism of the rolled material, seam flaw depth, and end face shape of the rolled material; Fig. 2 is a drawing showing the relationship between the shape ratio α and the end face shape; Figure 3 (a) is a schematic side sectional view of the Etzling roll 1 with a gulliver. Figure 3 (bl
is a schematic side sectional view of the inclined roll. l...Edging roll with gulliver, 2... Chamfering amount, 3... Inclined roll, 4... Hydraulic cylinder, S
... Rolled material, R... Chamfering curvature. Agent Patent attorney Masamitsu Akizawa and one other person left 1 Figure 0 20 40 60 80 10o t20t
m t6o zBO board rhinoceros (/rnn) 72 Figure 3 Figure Cb)

Claims (2)

[Claims] (1) At least one pair of horizontal rolls and one pair of vertical rolls are arranged to perform shape adjustment rolling and widening rolling of the material to be rolled.
and when manufacturing a steel plate by performing finish rolling, in the finish rolling of the rolled material, at least one pass of rolling is performed before or after a horizontal pass in which the end face shape of the rolled material bulges due to width expansion, or in each of the front and rear passes. A method for manufacturing a steel plate with excellent edge quality, characterized by chamfering rolling the corners of the material. (2) The edge according to claim 1, in which at least one pass of corner chamfer rolling of the rolled material is performed before or after the horizontal pass in which the shape ratio α becomes 1.0 or more for the first time, or before and after each of the horizontal passes. A method for manufacturing steel sheets with excellent quality.