JPH1034237A - Production of cold rolling stainless steel sheet with excellent flatness - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove the twist generating in the case of cutting in a long bar in the rolling direction by cutting a finishing cold rolling stainless steel strip in the long bar in the rolling direction and straightening the flatness with a tension leveler. SOLUTION: The twist generation is caused on a few influence of an intermediate cold rolling and on a finishing cold rolling. Then it is straightened effectively with a tension leveler after cold rolling, the effect to straighten it as it is cold finished is made a remarkably few, however when it is straightened after cutting it in the bar, the remarkable effect is realized. Further, cutting the finishing cold rolled stainless steel strip in the long bar to the rolling direction is in order to obtain the long bar and to minimize the change of residual stress in the longitudinal direction of the bar, and to easily make the post flatness straightening. Therefore, by applying the tension leveler on it after cutting in the bar, the effect of straightening the twist is made large.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a cold-rolled stainless steel sheet having excellent flatness, which is mainly used as a material for parts of electric and precision equipment and office equipment.

[0002]

2. Description of the Related Art A thin cold-rolled stainless steel sheet having a thickness of about 0.1 to 0.3 mm, which is used for a floppy disk shutter or a leaf spring, is a hot-rolled stainless steel sheet which has been annealed, pickled and scratched. It is manufactured by the following method using a steel strip as a raw material. That is, after cold rolling (intermediate rolling) -annealing (intermediate annealing) -pickling is repeated an appropriate number of times to adjust the sheet thickness,
This is a method in which finish annealing, pickling, or bright annealing is performed, and then finish cold rolling is performed at a predetermined reduction (working rate) in order to impart target mechanical properties.

[0003] The cold-rolled stainless steel sheet (hereinafter, referred to as a stainless steel sheet) manufactured as described above is usually cut into 2 to 10 strips having an appropriate width and long in the rolling direction, thereby forming an intermediate material. The strip material is punched into a product shape by a press and subjected to bending and the like to produce a product.

[0004] If the flatness of the intermediate material is poor, the dimensional accuracy and shape required for the product cannot be obtained, or smooth pressing cannot be performed. Since the flatness of the strip material often depends on the flatness of the intermediate cold-rolled stainless steel strip, the thickness accuracy and flatness of the intermediate cold-rolled stainless steel strip are important.

Conventionally, in order to improve the flatness of the intermediate cold-rolled stainless steel strip, after annealing the intermediate cold-rolled material, the flatness is corrected by a tension leveler, and after the finish rolling, the flatness is not corrected. Had been commercialized. In such a method, even if the plate shape after finish rolling is apparently flat, if it is cut (slit) into a strip by narrowing it to the product width, the following "twist" occurs, resulting in poor flatness. Was. No twisting was observed in the strip at the center in the width direction of the steel strip, but twisting became remarkable as approaching both ends, thereby deteriorating the product yield.

FIG. 1 is a view showing the shape of a cold-rolled steel sheet. When a steel sheet having an appropriate length in the rolling direction is cut out from the steel strip after the finish cold rolling and observed in a stationary state, one short side L perpendicular to the rolling direction becomes convex upward and the other short piece. R has a downwardly convex shape. When a steel strip of such a shape is cut into a plurality of strips long in the rolling direction,
The flatness of the strip taken from the center of the width of the steel strip is relatively good, but the strip taken from near the edge is twisted. This torsion does not appear in the cold rolled steel strip as it is, which is a potential flat defect of the cold rolled steel strip.

FIG. 2 is a view for explaining a state of twisting appearing in the strip.

[0008] "Twist" is a strip 8 of a specific length from the strip material.
Is cut out and fixed to one of the short sides of the strip 8 on a vertical plane, and when the reference projection length from the strip 8 to the vertical plane 7 is S, the two ends of both ends of the strip are Points a, b
From the vertical plane 7 measured in the horizontal direction from the distance da,
Indicates a state where a difference occurs in db. Therefore, the “torsion amount” is evaluated by the absolute value | da−db | of the difference.

As a countermeasure for preventing the twist, a method of reducing the twist by adding a tension leveler step after finish rolling is adopted. However, a sufficient straightening effect could not be obtained due to the high yield stress of the cold-rolled stainless steel strip. In addition, it is difficult to set conditions with a tension leveler, and it is necessary to set the conditions for each coil, and at present, it is impossible to completely prevent the occurrence of torsion.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for removing the twist generated when a finish cold-rolled stainless steel strip is cut into a long strip in the rolling direction.

[0011]

The present inventors have conducted various experiments and studies on a method for removing a twist generated when a finish cold-rolled stainless steel strip is cut into a long strip in the rolling direction. The following findings were obtained.

1) The cause of the twist is little affected by the intermediate cold rolling and is caused by the finish cold rolling.

2) Therefore, it is effective to correct by a tension leveler after finish cold rolling, and even if the straightening is performed with the sheet width as it is, the effect is extremely small.
After cutting into strips, the effect is remarkable when straightened.

The present invention has been made on the basis of such knowledge, and the gist of the invention is to “cut a finish cold-rolled stainless steel strip into a strip that is long in the rolling direction, and then apply the strip to a tension leveler. A method for producing a cold-rolled stainless steel sheet having good flatness, wherein the flatness is corrected by using the method described above.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Cutting a finish cold-rolled stainless steel strip into a long strip in the rolling direction is intended to obtain a long strip and to reduce the change in residual stress in the length direction of the strip. This is to facilitate flatness correction later.

That is, when the strip is cut into a long strip in the width direction of the stainless steel strip, the length of the strip is limited to the width of the stainless steel strip, and the strip cannot be longer than the width of the steel strip. Also, as described above with reference to FIG. 1, the flatness in the width direction is worse than the flatness in the rolling direction because the change in the residual stress in the width direction of the steel strip is large.

In the present invention, after the strip material is cut, it is applied to a tension leveler in order to increase the effect of correcting the twist.

If a tension leveler is applied with a wide width as it is after finish rolling as in the conventional method, a sufficient twist cannot be corrected.

It is not clear why the effect of correcting the torsion increases when the finished cold-rolled stainless steel strip is cut into strips and then applied to a tension leveler.

The width of the finish cold-rolled stainless steel strip is usually about 500 to 1000 mm. The width of the strip to be cut varies depending on the product, but is about 50 to 150 mm
Range.

The tension leveler used in the method of the present invention can use a small diameter and short roll because the material to be corrected is narrow. Diameter 12 ~ 15mm, length 200 ~
It is preferably about 400 mm. Since the roll is a small-diameter roll, a backup roll is preferably used to suppress the deflection of the roll.

The tension leveler conventionally used has a diameter of 15 to 40 mm and a length of 800 to 13.
A roll of about 00 mm is used. Such a tension leveler cannot be used because it is designed to straighten a wide stainless steel strip that has been finished cold rolled.

Applying tension to the steel strip at the time of straightening by the tension leveler is the same as in the conventional tension leveler. The magnitude of the tension varies depending on the roll diameter, the number of rolls to be used, the amount of reduction, and the like.
For a roll of about ² mm, the pressure is preferably about 22 kg / mm ² or more.

The stainless steel targeted by the method of the present invention is a stainless steel for springs, and is SUS301-CPS.
And SUS304-CSP are preferable.

Hereinafter, the effects of the present invention will be described based on examples.

[0026]

EXAMPLE Two hot-rolled coils of austenitic stainless steel SUS 304 having a thickness of 3 mm and a width of 680 mm were used.
Annealing at 1100 ° C, pickling, and cold rolling were performed. Cold rolling is rolling to a sheet thickness of 0.161 mm by intermediate cold rolling,
Then, the sheet was finished to a thickness of 0.15 mm by cold rolling.

One cold-rolled coil (hereinafter referred to as coil A) having a slit line width of 68 mm
It was cut into nine strips long in the rolling direction. A-1 to A9 are attached to each strip in order from one edge side of the steel strip,
Five strips A-1, A-2, A-8, A-9 on both edges and A-5 at the center of the steel strip were flattened by a tension leveler under the following conditions.

Tension leveler: (work rolls) Number: 19 (9 upper, 10 lower) Diameter: 12 mm Pitch: 16 mm Surface length: ··· 300 mm Material ··· SKD11 Hardened hardness ··· HS75 (back-up rolls) Number ······· 84 (40 upper, 44 lower) Note pitch · · · · · · 16 mm face length · · · · · · 9 mm × 2 material · · · · · · SUS440 hardness ·· HS60~65, tension at 22 Kg / mm ^2, lubricant is not used dry Was corrected.

After completion of the straightening, the length of each strip is 1200 mm.
A torsion measurement test piece was collected, and was subjected to the method shown in FIG.
Twist da and db were measured, and the difference was evaluated as the amount of twist. In addition, the distance S indicating the measurement position of the test piece was set to 700 mm and 1000 mm, which are often requested by the user.

As a comparative example, the other coil (hereinafter, referred to as coil B) was straightened by a tension leveler under the following conditions in a state where the finish was cold-rolled.

(Work rolls) Number ·············· 23 (11 upper, 12 lower) Diameter ······ 20 mm Pitch ······ 25 mm Surface length ······・ 700mm material ・ ・ ・ ・ ・ ・ ・ SKD11 Hardened hardness ・ ・ HS75 After straightening, width is 6 in slit line like coil A.
It was cut into 9 strips of 8 mm long in the rolling direction. Each strip is numbered B-1 to B-9 in order from one edge of the steel strip, and B-1, B-2, B-8, B-
9 and 5 strips of B-5 in the center of the steel strip, length 12
A 00 mm torsion measurement test piece was sampled, and the torsion was evaluated in the same manner as described above. In addition, the measurement position of the test piece also set S to 700 mm and 1000 mm similarly to the above.

Table 1 shows the measurement results.

[0033]

[Table 1]

As is clear from Table 1, when S is 1000 mm in the example of the present invention, the amount of twist is 4 mm or less, whereas in the comparative example, the amount of twist is 10 mm, which is much larger than that of the example of the present invention. .

The symbol B in Table 1 shows the result of measuring a twist amount of a test piece having a length of 1200 mm from a part of the coil B before cutting the coil B into a straightened strip using a tension leveler.

Symbol B indicates that the amount of twist is small and the correction effect is obtained by the tension leveler.
As is clear from the result of -9, twisting appears when the strip is cut.

[0037]

According to the present invention, there is obtained an extremely excellent effect that the twist of the strip material in the state of the intermediate material is almost eliminated and the yield is greatly improved.

[Brief description of the drawings]

FIG. 1 is a view showing the shape of a cold-rolled steel sheet.

FIG. 2 is a view for explaining a state of a twist appearing on a strip.

Claims (1)

[Claims] 1. A cold-rolled stainless steel strip having excellent flatness, wherein a cold-rolled stainless steel strip is cut into strips which are long in the rolling direction, and then the strips are flattened by a tension leveler. Steel plate manufacturing method.