JPH09263904A - Ferrite single phase stainless steel excellent in surface property - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a ferrite single phase stainless steel excellent in workability and furthermore excellent in ridging resistance. SOLUTION: This ferrite single phase stainless steel is the one having a compsn. contg. 0.015 to 0.050% C, <=0.5% Si, <=0.5% Mn, <=0.04% P, <=0.004% S, <=0.3% Ni, 16.0 to 18.0% Cr, 0.3 to 0.5% Nb, <=0.02% N, and the balance iron with inevitable impurities, and in which the weight ratio of Nb/C is regulated to 15 to 30.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ferritic single phase stainless steel which has excellent workability and ridging resistance.

[0002]

2. Description of the Related Art Molding,
Examples of steels having excellent corrosion resistance include high-purity ferato stainless steels to which Ti, Nb, Zr, etc. have been added. That is, it is effective to improve the formability and corrosion resistance by adding Ti, Nb, Zr, etc. as a fixed element of C, N and a carbonitride compound forming element for controlling the texture together with the suppression of C, N. It is generally known.

However, the addition of Ti or Zr results in the formation of huge clusters by combining with oxygen or nitrogen in the steel during steelmaking, resulting in defects such as flaws in the product, limiting its use. .

On the other hand, when Nb is added, the inclusions are finely dispersed, so that the occurrence of flaws is avoided, but on the other hand, it is considered that the crystal grains are coarsened in the central portion of the thickness of the hot rolled sheet during processing. Ridging occurs, resulting in problems in the surface properties after processing.

As a measure against ridging when Nb is added, in JP-A-56-123327, a finishing temperature of 85 is used.
Hot rolling at 0 ° C or lower, then annealing at annealing temperature 950
It is disclosed that it is continuously performed at 1050 ° C., and then cold rolling and recrystallization annealing are performed by a conventional method.

[0006]

Problems to be Solved by the Invention JP-A-56-1233
In No. 27, it is said that it is effective when processing such as steel for automobile moles is tensile bending, but when deep drawing is performed, for example, when it is processed into a commercial sink, it becomes parallel to the rolling direction. Ridging occurs, and it takes a huge amount of time and cost to remove it by polishing, and when it is severe, necking may occur and work cracking may occur.
Nb-added ferritic stainless steel for deep drawing, especially steel having sufficient characteristics for use as a sink, has not been obtained.

[0007]

As a result of various experimental studies on a method for enhancing resistance to ridging under such a background, it has been found that by adjusting the composition of steel, particularly C and Nb, ferrite single crystals having excellent ridging property can be obtained. It has succeeded in obtaining a phase stainless steel.

That is, according to the present invention, C: 0.015 to 0.
050%, Si: 0.5% or less, Mn: 0.5% or less,
P: 0.04% or less, S: 0.004% or less, Ni:
0.3% or less, Cr: 16.0 to 18.0%, Nb:
A ferrite single-phase stainless steel containing 0.3 to 0.5%, N: 0.02% or less, and the balance being iron and inevitable impurities, and having Nb / C (weight ratio) of 15 to 30. It is a ferritic single-phase stainless steel with excellent surface properties. ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the ferrite single phase stainless steel which is excellent in deep drawability of a sink etc. and corrosion resistance, and is excellent in the surface property after processing.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The reason why the steel of the present invention is limited to the above components will be described in detail below. C is an element that characterizes the present invention, and is an element necessary for suppressing ridging, so at least 0.015% is necessary. However, if it is contained in a large amount, an austenite phase is generated in a high temperature region, continuous annealing cannot be performed after hot rolling, and box annealing must be performed, which leads to an increase in cost, so the content is made 0.050% or less.

Si is a strong deoxidizing element and is added during the refining of steel. However, if added in a large amount, SiO ₂ non-metallic inclusions remain, which is unfavorable for the forming process and is 0.5% or less. . Mn is 0.5% or less for the same reason.

If P exceeds 0.04%, the formability is impaired, and S is 0.004% or less from the viewpoint of corrosion resistance.

Ni is an austenite forming element, and if contained in a large amount, an austenite phase is formed at high temperatures, so the content is made 0.3% or less.

[0013] Cr is an element necessary for improving corrosion resistance, but at least 1 is used from the viewpoint of corrosion resistance for use in sinks.
6.0% is necessary, and the upper limit is 18. from the viewpoint of workability.
0%.

Nb is an element necessary from the viewpoint of workability and corrosion resistance, and is required to be at least 0.3%. However, a large content increases hardness and impairs workability, so the content is made 0.5% or less. Regarding Nb / C (weight ratio), if the weight ratio is too high, ridging is remarkably generated, and if the weight ratio is too low, the ferrite single phase is not formed and the range is 15 to 30.
If a large amount of N is contained, a nitrogen compound of Nb is formed and a flaw is generated, so the content is made 0.02% or less.

[0015]

EXAMPLES Examples will be described below. The ferritic single-phase stainless steels listed in Table 1 were melted and continuously cast, and then the extraction temperature was 1150 to 1250 ° C and the finishing temperature was 85.
After rolling at 0 ° C. or lower and a coiling temperature of 300 to 450 ° C., continuous annealing was performed, and cold rolling annealing was performed twice or more to manufacture a cold rolled sheet having a thickness of 0.56 mm. Steels 1 to 3 are example steels having a composition within the scope of the present invention, and steels 4 to 6 are comparative steels.

[0016]

[Table 1]

Table 2 shows a ridging test in which each steel produced in the examples is subjected to a tensile deformation of 20% in the rolling direction to evaluate the ridging generated on the surface, using a JIS 13B test piece, a tensile test and deep drawing. The result of having measured the rank rate value which is an index of sex is shown.

[0018]

[Table 2]

20 tensile test pieces of the present invention steel and comparative steel were prepared.
%, And then polished 20 times with # 1000 abrasive paper and evaluated by ridging by the comparative method. As a result, the ridging obtained from the steel of the present invention is cold rolled twice and is A rank. Also,
The product cold-rolled three times was ranked A, and Ra also showed a lower value than the product cold-rolled twice. A comparative steel cold rolled twice is ranked D, and a cold rolled three times is ranked C to B.

The steel of the present invention and the comparative steel were processed into JIS No. 13B, and the rank value was measured. As a result, the rank value of the steel sheet cold-rolled 3 times was 1.7 to 1.8 for the steel of the present invention. Yes, the comparative steel is equivalent to 1.6 to 1.7.

The plate thickness is 0.56 mm × 740 mm × 9
Using a 70 mm plate, depth 180 mm, length 400 mm,
When processed into a sink with a width of 670 mm, the comparative steel has necking or cracking, whereas the steel of the present invention has no necking or cracking, less ridging, and good press results can be obtained. It was

[0022]

According to the product of the present invention, a ferrite single-phase stainless steel having excellent ridging resistance and excellent formability can be obtained.

Claims (1)

[Claims] 1. C: 0.015 to 0.050%, Si:
0.5% or less, Mn: 0.5% or less, P: 0.04% or less, S: 0.004% or less, Ni: 0.3% or less, C
r: 16.0 to 18.0%, Nb: 0.3 to 0.5%,
N: 0.02% or less is contained, the balance is ferritic single phase stainless steel consisting of iron and inevitable impurities,
Nb / C (weight ratio) is 15 to 30. Ferrite single-phase stainless steel with excellent surface properties.