JPH01138015A - Manufacture of stainless steel material - Google Patents

Abstract

PURPOSE:To obtain the stainless steel material excellent in surface properties and without a surface irregularity by performing drawing after the case cutting before the solution heat treatment. CONSTITUTION:The drawing is performed after the case cutting, the working irregularity of the surface layer caused by the case cutting is removed to obtain an uniform surface layer to prevent generating any selective corrosion at the time of pickling after the solution heat treatment. More, because if the draft of the drawing is too small, its effect is rather invalid, so the drawing is performed using a fixed die in the draft of at least by 3%. Therefore, the plastic working of the surface layer is performed uniformly.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a stainless steel material that is free from unevenness and has beautiful surface properties.

[Conventional technology] Conventionally, nickel-based (austenitic) stainless steel wire rods have been subjected to skin-shaving treatments such as peeling, warping, and ear broaching after rolling to remove black scales and surface flaws. After that, a solution heat treatment is performed to dissolve the carbide in the base material. After solution heat treatment,
A pickling treatment is performed again to remove scale adhering to the surface, and the product is completed as a stainless steel wire rod with a beautiful surface quality.

[Problems to be solved by the invention] When a stainless steel material is subjected to skin shaving, during pickling after solution heat treatment, some parts are preferentially corroded by acid locally, resulting in so-called uneven skin. As a result, a decrease in strength and a decrease in commercial value occurred due to deterioration of surface properties.

The present invention provides a method for manufacturing a stainless steel material with a beautiful surface texture by preventing the skin unevenness that inevitably occurs in the conventional process.

Structure of the Invention [Means for Solving the Problems] A method for manufacturing stainless steel materials according to the present invention, which has been accomplished to solve the above problems, includes the following steps: This is a special effect in which drawing is performed after skin shaving and before solution heat treatment.

Here, the drawing process after skin shaving and before solution heat treatment is
It is preferable to use a fixed die that allows uniform plastic working.

[Operation] When a rolled stainless steel material is shaved, regardless of whether peeling or wire broaching is used, it is inevitable that the surface layer will become partially non-uniform. It is thought that this unevenness in partial processing causes selective corrosion strength during pickling after the solution heat treatment, causing unevenness in the skin.

In the present invention, the drawing process after skin shaving removes the non-uniformity of surface layer processing due to skin shaving, and a uniform surface layer is obtained in terms of processing degree, so selective corrosion occurs during pickling after solution heat treatment. It is understood that this does not occur. For this reason, if the processing rate of the drawing process is too small, no effect will be observed, and it is desirable to perform the drawing process at a processing rate of at least three times.

[Example] In order to investigate the effect of improving the surface layer by the manufacturing method of stainless steel material of the present invention, 5US304 stainless steel 17
After rolling and skinning mmφ coil material and before solution treatment, drawing was not performed (AI, A2), drawing was performed using a roller die (81, B2), and drawing was performed using a fixed die. (CI, C2), the surface was visually inspected over the entire length of the coil weighing 1 ton, and the non-occurrence rate (pass rate) of surface layer unevenness was calculated. The results are shown in Table 1.

In Table 1, R is the state immediately after rolling, ST is solution heat treatment,
WB is wire broaching treatment (shaving treatment), CA is lime film formation treatment (for roller die drawing), WDR is roller die drawing treatment, 50S is pickling treatment, DPS is (for fixed die drawing) film formation for stainless steel. Process, WD indicates fixed die drawing process. The processing rate of the drawing process was 10% in both cases. Moreover, the pass rate is the ratio of the number of coils in which skin unevenness did not occur out of the total number of coils, expressed as a percentage.

-3= Among the various processes in Table 1, the process in which solution treatment is performed only once (
Comparing AI, Bl, C1), those that have undergone some kind of drawing process before solution treatment (Bl, C1) have a higher pass rate than those that have not undergone any drawing process (A1). Even when comparing the processes performed twice (A2, 82.C2), the pass rate of those that underwent drawing processing (82, C2) was higher than those that did not (A2).

Also, among drawing processes, those that have undergone drawing using a fixed die have a higher pass rate than those that have undergone drawing using a roller die, regardless of whether the solution treatment is performed once or twice. is high. This is because the drawing process using a roller die applies pressure in two stages vertically and horizontally, whereas the drawing process using a fixed die receives a predetermined uniform process in one step.
This is thought to be because plastic working is performed more uniformly in the surface layer.

In addition, although the above-mentioned example showed an example only about a coil wire material, it cannot be overemphasized that a bar material has a similar effect.

Effects of the Invention By the method for manufacturing stainless steel materials according to the present invention, conventionally,
The incidence of skin unevenness after pickling, which often occurs in the process where all skin shavings are subjected to solution heat treatment, is reduced, and stainless steel materials with beautiful surface properties can be manufactured.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a stainless steel material in which a solution heat treatment is performed after skinning, the method comprising performing a drawing process after skinning and before the solution heat treatment. 2. The method for manufacturing a stainless steel material according to claim 1, wherein drawing is performed using a fixed die after skin shaving and before solution heat treatment.