JP2001158944A - Method for producing austenitic stainless steel sheet for press forming in which orange peel is hard to be generated - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing an austenitic stainless steel sheet good in workability, and in which orange peel is hart to be generated. SOLUTION: At the time of subjecting an austenitic stainless steel slab to hot rolling, thereafter executing cold rolling and then subjecting the same to finish annealing, by controlling the crystal grain size number (N) of the steel sheet after the finish annealing to 8.5 to 9.5, the production of the austenitic stainless steel sheet for press forming in which orange peel is hard to be generated is made possible. In this case, it is perferable that the soaking temperature in the finish annealing is controlled to 1,040 to 1,060 deg.C, the soaking time is controlled to 20 to 50 s, and the control of the crystal grain size number is made more secure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an austenitic stainless steel sheet, and more particularly to a method for manufacturing an austenitic stainless steel sheet for press forming. The steel sheet according to the present invention includes a steel strip.

[0002]

2. Description of the Related Art Austenitic stainless steel has excellent formability, corrosion resistance, and weldability as compared with ferritic stainless steel, and is therefore widely used for building materials, sinks, and the like after press forming. Therefore, it is required that the austenitic stainless steel has excellent formability as a characteristic value, and that surface roughening such as orange peel does not occur during deep drawing.

[0003] Orange peel refers to an orange-skin-like uneven skin that appears at the bottom of a deep-drawing cup during deep-drawing molding.
It is known that this usually occurs when the crystal grain size is larger than a certain value, in other words, when the crystal grain size number is smaller than a certain value. On the other hand, it is known that the so-called deep drawability decreases when the crystal grain size is too small, because the elongation of the steel material deteriorates. Therefore, in the production of austenitic stainless steel sheets, taking into account these circumstances, the crystal grain size is controlled by combining various production factors, thereby satisfying both workability such as deep drawability and surface properties after processing. It is an issue to obtain a steel sheet that can be used. Such proposals include, for example, JP-A-8-501352, JP-A-9-3605, and JP-A-10-36922.

[0004]

By these proposals, it should be possible to produce an austenitic stainless steel sheet which satisfies both the workability and the surface properties of a deep drawn product. However, in reality, various manufacturing factors,
For example, variation in composition and variation in austenite stability (Md ₃₀ ) based on it, and variation in rolling conditions, especially the rolling speed at the beginning and end of rolling, cause variations in crystal grain size, and the bottom of the cup tends to be roughened during deep drawing tests. Become. For this reason, the crystal grains are small, in other words, the crystal grain size number has to be increased, resulting in sacrificing the workability.

An object of the present invention is to solve the above-mentioned problems of the prior art and to propose a method for producing an austenitic stainless steel sheet which is difficult to cause roughening represented by workability and orange peel.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have determined the range of crystal grain size in which orange peel is unlikely to occur from the results of a field survey and determined annealing conditions that can realize the crystal grain size. Thus, the present invention has been completed. That is, in the present invention, when austenitic stainless steel slab is hot-rolled, then cold-rolled, and then subjected to finish annealing to produce an austenitic stainless steel sheet, the grain size number of the steel sheet after finish annealing (N) Is adjusted to 8.5 to 9.5 to enable production of an austenitic stainless steel sheet for press forming in which orange peel is unlikely to occur. In this case, the soaking temperature of the finish annealing is set to 1040 to 1060 ° C, and the soaking time is set to
The grain size number is preferably adjusted to 20 to 50 s.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The steel to which the present invention is applied is 18% Cr-8%
Austenitic stainless steel containing Ni as a basic component. This includes SUS304 steel specified in JIS, as well as various additional elements, such as 0.5% or less Mo, 0.5% or less Cu, 0.03% or less Ti, 0.1% or less Nb, 0.020% B below
Etc. may be added.

The steel having the above composition is melted by an existing refining method typified by AOD, VOD, etc., then formed into a slab by an ingot casting method, a continuous casting method, etc., then hot-rolled, and then annealed. Further, after the surface is cleaned by pickling, it is subjected to cold rolling. These means are not particularly limited unless they impair the effects of the present invention.

[0009] The steel sheet whose final thickness is obtained by cold rolling is as follows:
Then, it is subjected to final finish annealing. The final finish annealing is generally performed in a continuous annealing furnace, in which the grain size number of the steel sheet is adjusted to 8.5 to 9.5.

[0010] These conditions are obtained from the manufacturing conditions of a steel sheet that does not generate orange peel in the deep drawing process. In other words, when investigating the relationship between the occurrence of orange peel and the grain size of the steel sheet in the deep drawing process of austenitic stainless steel sheet, the occurrence of orange peel disappears when the grain size number (N) specified in JIS G0551 is 8.5 or less. . However, the grain size number (N)
If it exceeds 9.5, as shown in FIG. 1, the elongation percentage of the steel sheet will be less than 54%, and if it is less than 54%, a decrease in workability cannot be tolerated. Therefore, although it depends on the deep drawing conditions, it is preferable to make the crystal grains as large as possible.

A known method can be used to adjust the crystal grain size number. For example, as disclosed in JP-A-10-36922, austenite stability (Md ₃₀ ),
Cold rolling reduction (Re), soaking temperature in finish annealing (Ts
s), soaking time (ts), etc., can be controlled to control the crystal grain size. In particular, among the finishing annealing conditions, it is most effective to set the soaking temperature during soaking in a narrow range of 1,040 to 1,060 ° C and the soaking time between 20 to 50 s.

The present invention is characterized in that the generation limit of orange peel is set in relation to the grain size, annealing conditions that give the largest grain size among them are selected, and the steel sheet is annealed accordingly. Thereby, in the deep drawing step of the steel sheet, no orange peel is generated, and the crystal grain size is maintained at a maximum, so that the workability of the steel sheet is kept high.

[0013]

[Example] C: 0.05%, Si: 0.03%, Mn: 1.0%, P: 0.03%, S:
0.01%, Cr: 18.2%, Ni: 8.7%, Al: 0.02%, N: 0.04%, Mo:
0.1%, Cu: 0.3%, 0.8mm thick cold rolled austenitic stainless steel sheet having a composition substantially composed of Fe excluding the balance of impurities obtained by performing hot rolling and cold rolling according to a conventional method. A plate was obtained and the final finish annealing was performed at a soaking temperature of 1050.
C. and a soaking time of 30 seconds. As a result, the crystal grain size number 8.
Seven steel plates were obtained.

The obtained steel sheet was used for applications including deep drawing, but no orange peel was generated, and the elongation was 57%.
%, And the workability was also good. On the other hand, in the case where the conventional orange peel countermeasures were taken, the crystal grain size number (N) was distributed to a slightly larger side, and although the occurrence of orange peel was not recognized, the elongation rate was 52%.
%, And the workability was insufficient.

[0015]

According to the present invention, since the grain size of the austenitic stainless steel sheet is adjusted to a grain size of 8.5 to 9.5, orange peel does not occur and workability is good.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the grain size number and the elongation percentage in an austenitic stainless steel sheet.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Hideaki Yamashita 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Inside the Chiba Works of Kawasaki Steel Corp. (72) Hideya Yoshizawa 1st Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Kawasaki 4K037 EA12 EA21 EB14 FJ07 4K038 AA01 BA01 CA01 DA01 EA02 FA01 4K043 AA01 AB12 AB23 AB24 BB02 BB04 DA05 EA02 FA03 FA07

Claims (2)

[Claims] 1. A hot rolled austenitic stainless steel slab, a cold rolled roll, and a finish annealing, wherein the grain size number (N) of the steel sheet after the finish annealing is adjusted to 8.5 to 9.5. A method for producing an austenitic stainless steel sheet for press forming, which hardly generates orange peel. 2. A soaking temperature of 1,040 to 1,060 for finish annealing.
The method for producing an austenitic stainless steel sheet according to claim 1, wherein the temperature and the soaking time are 20 to 50 s.