JPH07197200A - Austenitic stainless steel having small anisotropy in shape freezing quantity developed at the time of deep-drawing - Google Patents

Abstract

PURPOSE:To improve the accuracy of forming size at the time of deep-drawing after obtaining an austenitic stainless steel and to improve the material yield by specifying the component composition of an austenitic stainless steel and a SD value based on Ni, Mu, C and N contents uniquely deciding its anisotropy. CONSTITUTION:This austenitic stainless steel is composed of, by wt%, 0.005-0.10 C, 0.2-3.0 Si, 0.1-4.0 Mn, 12.0-25.0 Cr, 5.0-15.0 Ni, 0.05-5.0 Cu, 0.05-3.0 Mo, 0.01-0.15 N and the balance Fe. The SD value defined with the equation: SD =7.59+9.76XC-14.33XN-1.32XNi+4.14XMn, is made so as to satisfy -1<=SD<=1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an austenitic stainless steel having a small amount of shape freezing generated during deep drawing.

[0002]

2. Description of the Related Art Normally, austenitic stainless steel has the characteristics of high tensile strength steel in addition to its original corrosion resistance.
Moreover, it has excellent press formability. For this reason, it is very widely used as a building material, a family business equipment material, and an industrial machine material.

However, since austenitic stainless steel undergoes remarkable work hardening during deep drawing and the anisotropy of the amount of shape freezing that occurs during deep drawing, there is a need to anticipate a shape freezing margin before deep drawing. Yes,
It is necessary to thoroughly consider the material and dimensions of the product shape.

As a conventional technique considering the deep drawability of austenitic stainless steel, the deep drawability is excellent by suppressing the occurrence of ears after deep drawing or increasing the composition strain after deep drawing. Austenitic stainless steel has been proposed.

For example, in Japanese Examined Patent Publication No. 64-1528, the finish cold rolling rate is specified to be 30 to 50% under the manufacturing conditions of austenitic stainless steel, so that the occurrence of ears after deep drawing can be suppressed and Improves drawability. In Japanese Patent Publication No. 58-30373, the rolling reduction, rolling temperature, and heat treatment temperature of cold rolling are specified under the manufacturing conditions for austenitic stainless steel.
We have proposed austenitic stainless steel with good deep drawability by conducting a deep draw test on a rectangular tube and increasing the composition strain.

However, based on the concept of the anisotropy of the shape freezing amount generated during deep drawing, a technique for reducing the anisotropy of the shape freezing amount during deep drawing of austenitic stainless steel has been conventionally studied. Not not.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides an austenitic stainless steel characterized by having a small amount of shape freezing anisotropy generated during deep drawing, and forming dimensions during deep drawing. The purpose is to improve the material yield by improving the precision.

[0008]

As a result of investigating the component ranges with respect to the above, it has been found that the following component system is an essential condition. That is, in% by weight, C: 0.0
05-0.10%, Si: 0.2-3.0%, Mn:
0.1-4.0%, Cr: 12.0-25.0%, N
i: 5.0-15.0%, Cu: 0.05-5.0%,
Mo: 0.05-3.0%, N: 0.01-0.15
%, With the balance being inevitable impurities and Fe,
Further, the austenitic stainless steel is characterized in that the SD value defined by the following formula (1) satisfies the formula (2) and the anisotropy of the shape freezing amount generated during deep drawing is small.

SD = 7.59 + 9.76 × C-14.33 × N-1.32 × Ni + 4.14 × Mn (1) Formula −1 ≦ SD ≦ 1 (2) Formula SD in austenitic stainless steel It is more preferable that the value satisfies the expression (3).

−0.5 ≦ SD ≦ 0.5 Expression (3)

[0011]

The limited range of each of the above components in the present invention will be described below. The following% indicates% by weight.

C: C is an element that forms and stabilizes the austenite phase. If it is less than 0.005%, it is difficult to form the austenite phase, and the work-induced martensite transformation begins to occur from the beginning of processing, and the shape freezing amount is anisotropic. The nature becomes large. If the content exceeds 0.10%, the strength becomes excessively high,
The deep drawability itself is deteriorated, and the anisotropy of the shape freezing amount becomes large.

N: N is an element that forms and stabilizes the austenite phase, and is added in an amount of 0.01% or more in order to form the austenite phase and maintain the isotropic shape freezing amount. If it exceeds 0.15%, the strength becomes excessively high, the deep drawability itself deteriorates, and the anisotropy of the shape freezing amount becomes large.

Ni: Ni is an element that forms and stabilizes an austenite phase, and if it is added in an amount less than 5.0%, it is difficult to form an austenite phase, and an excessive martensite phase is formed at the time of cold pressure, and is anisotropic after annealing It becomes easy to get sexual.
When added over 15.0%, S is one of the SD value constituent elements.
The effect of reducing the D value is strongest, the deep drawability itself is deteriorated after annealing, the shape freezing amount in the rolling parallel direction is increased, and the shape freezing amount tends to be anisotropic.

Mn: Mn is added as an element that forms and stabilizes the austenite phase. The addition of 0.1% or more reduces oxygen in the steel, suppresses the concentration of strain on inclusions during rolling, and increases the isotropy after annealing. 4.0%
When added in excess of 4, the effect of increasing the SD value is the strongest among the SD value constituting elements, the deep drawing workability itself is deteriorated after annealing, and the shape freezing amount tends to be anisotropic.

Si: When Si is added in an amount of 0.2% or more,
Oxygen in steel is reduced, the concentration of strain in inclusions during rolling is suppressed, and the isotropy after annealing is increased. Addition of more than 3.0% deteriorates the deep drawability itself and increases the anisotropy of the shape freezing amount.

Cr: Cr is a basic component of stainless steel, and the anisotropy of the shape freezing amount after deep drawing is remarkable. 5.
With 0 to 15.0% added Ni and 12.0 to 25.0% added Cr, the isotropy during deep drawing becomes good.

Cu: Cu is an element that improves the workability of stainless steel and is effective in reducing the anisotropy of the shape freezing amount, so it is added in an amount of 0.05% or more. Even if added over 5.0%, anisotropy of the shape freezing amount cannot be expected to be reduced, so 5.0% is made the upper limit.

Mo: Mo is effective in reducing the anisotropy of the shape freezing amount, and is added in an amount of 0.05% or more. If the content exceeds 3.0%, the hardness becomes high, the deep drawing workability is remarkably deteriorated, and the anisotropy of the shape freezing amount tends to occur.

According to the present invention, when the relationship between the anisotropy of the shape freezing amount generated in the shape after drawing and the component is adjusted during deep drawing, the anisotropy is adjusted to the Ni, Mn, C, N amount. It was completed by finding that it is uniquely determined by. That is, the anisotropy of the shape freezing amount is reduced by adjusting the components so that the SD value of the following formula determined by the amounts of Ni, Mn, C, and N is −1 ≦ SD ≦ 1.

SD = 7.59 + 9.76 × C-14.33 × N-1.32
XNi + 4.14xMn Here, when the SD value is less than -1 and the SD value exceeds 1, the anisotropy of the shape freezing amount is too high, and both are inappropriate.

Further, not only the 2B material which has been subjected to the annealing pickling after cold rolling and the temper rolling, but also the 2D material which has been subjected to the annealing pickling after cold rolling and the No. 2 which has been subjected to annealing pickling after hot rolling The effect of the present invention is effective even with one material.

The effects of the present invention are Ni, Mn, C,
N, Si, Cr, Cu, Mo amount is in proper value, N
It is considered that when the amounts of i, Mn, C, and N satisfy a predetermined relational expression, a highly isotropic texture develops.

In addition to the specified components, V of 0.2% or less, Ca of 0.005% or less, P of 0.07% or less,
Even if it contains 0.001 to 0.01% S of one kind or two or more kinds, the effect of the present invention is not impaired at all.

Next, the present invention will be described in more detail based on examples.

[0026]

[Examples] Austenitic stainless steels (2B material, 2D material) having the chemical composition shown in Table 1 (inventive steel, comparative steel)
No. 1 material) was used to perform a deep drawing test. The test method is shown in FIG. The conditions of the deep drawing test are shown below.

Blank diameter 100 mm Die shoulder radius 5 mm Punch diameter 50 mm Die hole diameter 52.9 mm Punch radius 5 mm Anisotropy of shape freezing amount that occurs during deep drawing is the right angle of rolling of austenitic stainless steel after deep drawing. The ratio between the diameter in the direction (dC) and the diameter in the rolling parallel direction (dL) is shown.

Example 1 An austenitic steel having the chemical composition shown in Table 1 was used to perform a deep drawing test. In Table 1, 2B material (invention steels 1 to 20 and comparative steel 2) subjected to annealing pickling and temper rolling after cold rolling is shown.
7 to 44), as well as the 2D material (inventive steels 24 to 26, comparative steels 47 to 48) as-annealed after cold rolling and No. 7 subjected to annealing pickling after hot rolling. 1 material (invention steel 21-23, comparative steel 45-46) is included.

Table 2 (inventive steels, comparative steels) shows the test results of deep drawing. Comparative steel (30-35, 45-48)
Then, each element is within the specified composition range, but the SD value is -1.
Since it is out of the range of ≦ SD ≦ 1, the anisotropy of the amount of shape freezing generated during deep drawing is not improved. Comparative steel (27
.About.29), the SD value is within the range of -1.ltoreq.SD.ltoreq.1, but the anisotropy of the shape freezing amount generated during processing is not improved because the main element exceeds the specified component range. In the comparative steels (36 to 44), the main element exceeds the specified composition range,
Moreover, since the SB value is out of the range of -1≤SD≤1, the anisotropy of the shape freezing amount generated during deep drawing is not improved.

FIG. 1 is a plot of the relationship between the SD value shown in Table 2 and the anisotropy (dC / dL) of the shape freezing amount after the deep drawing test. Thus, the SD value is −
In the steel of the present invention in the range of 1 ≦ SD ≦ 1, the anisotropy of the amount of shape freezing that occurs during deep drawing is extremely small within 99.7 to 100.3. On the other hand, in the comparative steel, the anisotropy of the shape freezing amount is less than 99.7 or exceeds 100.3 and becomes large.

Example 2 Even if the relationship of the anisotropy (dC / dL) of the shape freezing amount after the two-stage deep drawing was investigated, the same effect of the present invention as in Example 1 could be exhibited.

[0032]

[Table 1]

[0033]

[Table 2]

[0034]

As is apparent from the above-described examples, the present invention has a smaller anisotropy of the amount of shape freezing that occurs during deep drawing than ordinary austenitic stainless steel by limiting the chemical composition. Austenitic stainless steel can be obtained, and the material yield can be improved by improving the forming dimensional accuracy during deep drawing.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between an SD value and anisotropy of a shape freezing amount after a deep drawing test.

FIG. 2 is a diagram showing a test method for anisotropy measurement of a shape freezing amount that occurs during deep drawing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Satoshi Ishijima 1-2 1-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.

Claims (1)

[Claims] 1. By weight%, C: 0.005 to 0.10%, Si: 0.2 to 3.0%, Mn: 0.1 to 4.0%, Cr: 12.0 to 25. 0.0%, Ni: 5.0 to 15.0%, Cu: 0.05 to 5.0%, Mo: 0.05 to 3.0%, N: 0.01 to 0.15%, However, the balance consists of unavoidable impurities and Fe, and the SD value defined by the following formula (1) satisfies the formula (2) and has a small anisotropy of the shape freezing amount that occurs during deep drawing. And austenitic stainless steel. SD = 7.59 + 9.76 × C-14.33 × N-1.32 × Ni + 4.14 × Mn (1) Formula −1 ≦ SD ≦ 1 (2) Formula