JP2970361B2 - Austenitic stainless steel with small anisotropy of springback generated during die bending - Google Patents

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 anisotropy in the amount of springback generated during die bending.

[0002]

2. Description of the Related Art Normally, austenitic stainless steel has the characteristics of high-strength steel in addition to its original corrosion resistance.
Also, it has excellent press formability. For this reason, it is very widely used as building materials, household equipment materials, and industrial machinery materials.

[0003] However, austenitic stainless steel undergoes remarkable work hardening during die bending, and has a large anisotropy in the amount of springback generated during die bending. For this reason, it is necessary to allow for a springback margin before the die bending process, and sufficient consideration is required for the material and dimensions of the product shape.

[0004] On the other hand, regarding the mold bending workability of ferritic stainless steel, the form of cracks in close contact bending,
From the viewpoint of the rebound angle after V-bending (90-degree bending), some stainless steels having excellent bending workability have been proposed.

For example, Japanese Patent Publication No. 54-35169 discloses a method of controlling the cleanliness of a ferritic stainless steel by adjusting the composition of the ferritic stainless steel so as to prevent the occurrence of cracks after close bending and to improve the mold bending workability. Have improved. Also,
In Japanese Patent Publication No. 51-35369, a specified amount of Ti is added in accordance with the contents of C and N in ferritic stainless steel, and the bending property with a small rebound angle after V bending (90 degree bending) is excellent. Stainless steel has been proposed.

However, based on the concept of anisotropy of the amount of springback generated during die bending, a technique for reducing the anisotropy of the amount of springback during die bending in austenitic stainless steel has been proposed. Absent.

[0007]

SUMMARY OF THE INVENTION According to the present invention, the material yield can be improved by reducing the anisotropy of the amount of springback generated during mold bending, thereby improving the molding dimensional accuracy during mold bending. An object is to provide an austenitic stainless steel.

[0008]

In order to achieve this object, the present invention relates to a method for producing C: 0.005 to 5% by weight.
0.10%, Si: 0.2 to 3.0%, Mn:
0.1 to 4.0%, Cr: 12.0 to 2
5.0%, Ni: 5.0 to 15.0%, Cu:
0.05 to 5.0%, Mo: 0.05 to 3.
0%, N: 0.01 to 0.15%,
An austenitic stainless steel with a balance of Fe, characterized in that the SB value defined by the following equation (1) has a small anisotropy in the amount of springback generated during mold bending processing that satisfies the following equation (2). Austenitic stainless steel. SB = 146.5 + 55.2 × C% + 125.1 × N% −17.9 × Ni% −1.1 × Mn% (1) −2 ≦ SB ≦ 2 (2) In the austenitic stainless steel, the SB value is (3). It is more preferable to satisfy the expression. -1 ≦ SB ≦ 1 (3)

[0009]

The limited range of each component in the present invention will be described below. Hereinafter,% indicates% by weight. C: C is an element that forms and stabilizes the austenite phase, and is effective for increasing the strength. 0.00
If it is less than 5%, it is difficult to secure a predetermined strength, and the refining cost increases. If the addition exceeds 0.10%, the strength becomes excessively high, the anisotropy of the amount of springback increases, and Cr carbide is easily formed at the grain boundary, so that the corrosion resistance is significantly deteriorated.

N: N is an element that forms and stabilizes the austenite phase, and is added in an amount of 0.01% or more to improve the strength of stainless steel. In addition to increasing the anisotropy, the strength is excessively increased, and the productivity is reduced.

Ni: Ni is an element that forms and stabilizes the austenite phase. If the addition is less than 5.0%, an excessive martensite phase is generated at the time of cold pressure, and anisotropy is easily formed after annealing. Further, in order to improve corrosion resistance together with Cr, addition of 5.0% or more is required. If the addition exceeds 15.0%, anisotropy tends to be formed after annealing.

Mn: Mn is added as an element for forming and stabilizing an austenite phase. By adding 0.1% or more, oxygen in steel is reduced, concentration of strain on inclusions during rolling is suppressed, and isotropy after annealing is increased. 4.0%
If added, the anisotropy tends to be formed after annealing and the corrosion resistance is deteriorated.

Si: When Si is added in an amount of 0.2% or more,
Oxygen in steel is reduced, concentration of strain in inclusions during rolling is suppressed, and isotropy after annealing increases. If the addition exceeds 3.0%, the bendability itself deteriorates.

Cr: Cr is a basic component of stainless steel, and if it is less than 12.0%, the corrosion resistance is poor and the anisotropy of the springback amount after the bending of the mold is remarkable. 25.0
%, The anisotropy of the springback amount is apt to be provided, the hot workability is deteriorated, and the production becomes difficult.
5.0 to 15.0% added Ni and 12.0 to 25.0%
With the added Cr, the isotropy at the time of mold bending is good.

Cu: Cu is an element that improves the workability of stainless steel, and is effective in reducing the anisotropy of the amount of springback. Therefore, Cu is added in an amount of 0.05% or more. Even if added in excess of 5.0%, a reduction in anisotropy cannot be expected, so 5.0
% As the upper limit.

Mo: Mo is effective in reducing the anisotropy of the amount of springback, and is also an element that improves the corrosion resistance of stainless steel. Therefore, Mo is added in an amount of 0.05% or more. If the addition exceeds 3.0%, the alloy becomes hard and the bending workability remarkably deteriorates, and it becomes expensive, so the upper limit is 3.0%.

The present invention further provides an SB based on equation (1).
The value is set to −2 ≦ SB ≦ 2. The present invention relates to V-bending, U-bending,
While adjusting the relationship between the component and the anisotropy of the amount of springback that occurs at the time of the die bending process typified by the bending process, this anisotropy is uniquely determined by the amounts of Ni, Mn, C, and N. It has been found experimentally that it is done. Although the reason is not clear, Ni, Mn,
When the expression (1) constituted by the C and N amounts is within a predetermined range, a more isotropic texture is formed,
It is assumed that the anisotropy is reduced.

As described above, by adjusting the components so that the SB value satisfies −2 ≦ SB ≦ 2, the value determined from the amounts of Ni, Mn, C, and N, the anisotropy of the springback amount is reduced. Here, the amount of springback θ generated at the time of die bending indicates a deviation of a bending angle from 90 degrees after V bending in the case of V bending (90 degree bending). The anisotropy Δθv of the springback amount indicates a difference between the V bending angle in the direction parallel to the rolling direction and the V bending angle in the direction perpendicular to the rolling direction. In the present invention, the anisotropy Δθ of the amount of springback after V bending
v can be suppressed to 0.3 degrees or less in absolute value, preferably 0.2 degrees or less.

The amount of springback θ in the U-bend (180-degree bend) is 180 degrees after the U-bend.
The deviation of the bending angle from the degree is shown. The anisotropy Δθu of the amount of springback indicates a difference between the U-bending angle in the direction parallel to the rolling direction and the U-bending angle in the direction perpendicular to the rolling direction. In the present invention, the anisotropy Δθu of the amount of spring back after the U-bending can be suppressed to an absolute value of 0.5 degrees or less, preferably 0.4 degrees or less.

Further, the bending process includes the V bending and the U bending.
The springback amount θ in the bending process is a deviation of the bending angle of the convex portion after the bending process. Anisotropy of the amount of springback Δθ
M indicates the difference between the bending angle in the rolling direction and the bending angle in the direction perpendicular to the rolling direction. According to the present invention, the anisotropy ΔθM of the springback amount after the bending process can be suppressed to 0.4 degrees or less, preferably 0.3 degrees or less.

In this case, if the SB value is less than -2, there is a problem that the amount of spring pack in the rolling direction becomes large. If the SB value exceeds 2, the amount of spring pack in the rolling parallel direction becomes large. Does not exhibit the intended effect of the invention.

It is to be noted that the present invention is not limited to a steel material (2B material) that has been subjected to annealing pickling and temper rolling after cold rolling, as well as a steel material (2D material) that has been subjected to cold rolling and annealing and pickling and annealed acid after hot rolling. It is also effective for the washed steel material (No. 1 material).

The present inventors have proposed Ni, Mn, C, N, Si,
Cr, Cu, and Mo amounts are at appropriate values, and Ni, Mn,
It is speculated that when the C and N contents satisfy a predetermined relational expression, a desired effect can be achieved because a highly isotropic texture develops.

In the present invention, in addition to the specified components, 0.1.
Even if it contains V of 2% or less, Ca of 0.005% or less, P of 0.07% or less, and S of 0.001 to 0.01%, the effect of the present invention is not impaired at all.

[0025]

Next, the present invention will be described in detail with reference to examples. Using austenitic stainless steel (2B material, 2D material, No. 1 material) having the chemical components shown in Table 1,
V-bending (90-degree bending) and U-bending tests, which are basic types of die bending, were performed.

Embodiment 1 The springback amount θ in the V-bending (90-degree bending) indicates a deviation of the bending angle from 90 degrees after the V-bending. The anisotropy Δθv of the amount of springback indicates the difference between the V bending angle in the direction parallel to the rolling direction of the austenitic stainless steel and the V bending angle in the direction perpendicular to the rolling direction. FIG. 1 shows SB
The relationship between the value and the anisotropy of the amount of springback after the V bending test is shown. As described above, in the steel of the present invention in which the SB value is in the range of −2 ≦ SB ≦ 2, the anisotropy Δθv of the amount of springback after the V-bending process is as extremely small as 0.3 degrees or less in absolute value. I have.

Example 2 FIG. 2 shows the relationship between the SB value and the anisotropy Δθu of the amount of springback after a U-bend (180-degree bend) test. As described above, in the steel of the present invention in which the SB value is in the range of −2 ≦ SB ≦ 2, the anisotropy of the springback amount after the U bending is Δθ.
The absolute value of u is as extremely small as 0.5 degrees or less.

A mold bending test was performed using an austenitic steel having the chemical composition shown in Table 1 (inventive steel) and Table 2 (comparative steel). In Table 1, 2B materials (invention steels 1 to 18, comparative steels 25 to 42) subjected to annealing pickling and temper rolling after cold rolling.
Not only, but also the 2D material that has been subjected to cold pickling and annealing pickling (invention steel 2)
Nos. 2 to 24, comparative steels 45 to 46) and No. 2 which were annealed and pickled after hot rolling. 1 material (Invention steel 19-21, Comparative steel 43-4)
4) is included.

Table 3 (inventive steel) and Table 4 (comparative steel) show the results of the die bending test. Comparative steel (25-32, 43
To 46), each element is within the specified component range.
Since the value is outside the range of −2 ≦ SB ≦ 2, the anisotropy of the amount of springback generated at the time of die bending is not improved. In the comparative steels (33 to 36), the SB value was −2 ≦ SB ≦ 2
However, since the main element exceeds the specified component range, the anisotropy of the amount of springback generated at the time of die bending is not improved. In comparative steels (37 to 42), the main element exceeds the specified component range, and the SB value is −2 ≦ SB
Since it is out of the range of ≦ 2, the anisotropy of the amount of springback generated at the time of die bending is not improved.

[0030]

As is clear from the above-mentioned embodiments, the present invention is characterized in that the chemical composition is limited to occur during the bending of a typical austenitic stainless steel in V bending and U bending. An austenitic stainless steel with small anisotropy in springback amount can be provided.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]

[Table 4]

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between an SB value and anisotropy of a springback amount after a V bending test.

FIG. 2 is a diagram showing a relationship between an SB value and anisotropy of a springback amount after a U bending test.

FIG. 3 is a diagram showing a test method for V bending and U bending.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Satoshi Ishijima 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Inside Nippon Kokan Co., Ltd. (56) References JP-A-5-287459 (JP, A) JP-A-61 -139651 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C22C 38/00 302 C22C 38/44 C22C 38/58

Claims (1)

(57) [Claims] C. 0.005 to 0.10%, Si: 0.2 to 3.0%, Mn: 0.1 to 4.0%, Cr: 12.0 to 25% by weight. 0%, Ni: 5.0-15.0%, Cu: 0.05-5.0%, Mo: 0.05-3.0%, N: 0.01-0.15%. , The rest F
e, an austenitic stainless steel characterized in that the SB value defined by the following formula (1) satisfies the following formula (2) and the anisotropy of the amount of springback generated during the bending process is small. Austenitic stainless steel. SB = 146.5 + 55.2 × C% + 125.1 × N% −17.9 × Ni% −1.1 × Mn% (1) -2 ≦ SB ≦ 2 (2)