JP2606922B2 - Manufacturing method of ferritic stainless steel strip - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for producing a building material for exterior use, in particular, a ferritic stainless steel strip formed into a thin plate and used for a roofing material.

[Conventional technology]

Stainless steel sheets are often used as exterior building materials in relatively small areas such as sashes, curtain walls and panels. However, in recent years, the corrosion resistance and weather resistance of stainless steel have been recognized, and they have come to be used as roofing materials in conjunction with the development of construction techniques.

In this case, as a roof material, a painted stainless steel plate is used, which is made of a stainless steel plate as a base material and is painted and colored. This is intended to overcome the drawback that the conventional tin roof becomes unusable due to a short-term leakage of water due to perforation if a coating defect occurs due to deterioration of the coating film.

As this painted stainless steel sheet, SUS304 (18Cr-8Ni), which is an austenitic stainless steel, has been mainly used because of its good workability.

However, with the above-mentioned coated stainless steel sheet, it is unknown whether the base material is stainless steel due to the coating film, and the maintenance of the stainless steel surface, such as the drawback of not being able to make use of the beauty and luxury of the surface, and the repainting accompanying deterioration of the coating film There was a problem that needed. Further, austenitic stainless steel contains a large amount of expensive Ni, so that the price is high, and it is difficult to increase demand.

However, when unpainted ferritic stainless steel is used as an exterior building material, especially as a roof material, sufficient outdoor weather resistance that does not cause corrosion such as pitting due to red rust or sea salt particle adhesion for a long period of 10 years or more. Corrosion resistance is inevitably required.

Austenitic stainless steels were relatively insignificant because of their good workability, but ferritic stainless steels, for example, had a bottom plate and side plates that were formed during roofing as shown in Fig. 1. A phenomenon called pocket wave (also called oil can) that becomes uneven tends to appear. This phenomenon is problematic because it impairs the appearance of the roof.

[Problems to be solved by the invention]

The present invention uses a ferritic stainless steel strip produced in the cold rolling process as a roofing material without painting, so that it has sufficient outdoor weather resistance and corrosion resistance, and can be formed without pocket wave phenomenon. An object of the present invention is to provide a method for forming a ferritic stainless steel strip having good workability.

[Means for solving the problem]

In order to solve the above-mentioned problems, the present invention provides a steel containing C: less than 0.1% by weight, N: less than 0.1% by weight, and Cr: 11 to 35% by weight. A method for producing a ferritic stainless steel strip, which is maintained at a temperature of 500 ° C. for 10 seconds to 3 minutes, wherein the steel according to claim 1 further comprises: Mo: 0.3 to 4% by weight and / or Cu: 0.3 to 0.3%. The method for producing a ferritic stainless steel strip according to claim 1, which contains 5% by weight, and the steel according to claim 1 or 2, further containing Nb: less than 1% by weight and / or Ti: less than 1% by weight. Item 1. A method for producing a ferritic stainless steel strip according to item 1 or 2.

[Action]

In general, a ferritic stainless steel strip is hot-rolled, then annealed and pickled, and is subjected to a single or intermediate annealing.
After cold rolling more than once, final annealing and temper rolling are performed to obtain a product.

The present inventors have conducted various studies on the deformation and the like shown in FIG. 2 which occur in the forming of the stainless steel strip, and as a result, have obtained the following knowledge and reached the present invention.

(1) From the viewpoint of mechanical properties, the forming phenomenon of the roofing material is the strain ratio in the small deformation area in the steel strip C direction ([tensile direction strain] / [width direction strain] in the C direction tensile test, hereinafter simply referred to as the strain ratio). Written as
When is increased, the residual tensile stress in the bent portion becomes small, and the compressive stress in the bottom plate becomes small. As a result, pocket waves are reduced.

(2) When the elastic limit in the direction of the steel strip C is increased, the deformation area of the bent portion becomes small, and the compressive stress of the bottom plate becomes small. As a result, the pocket wave is reduced.

That is, in order to achieve the object of the present invention, it is necessary to manufacture a ferritic stainless steel strip having outdoor weather resistance and corrosion resistance, a large strain ratio, and a high elasticity limit.

 Hereinafter, the reasons for limitation of each component will be described.

(A) C: less than 0.1% by weight C is preferably as small as possible because the moldability is improved. However, when the content is less than 0.1% by weight, there is no significant adverse effect, so the content is limited to less than 0.1% by weight.

(B) N: less than 0.1% by weight N is preferably as small as possible because the moldability is improved. However, if the content is less than 0.1% by weight, there is no significant adverse effect, so the content is limited to less than 0.1% by weight.

(C) Cr: 11 to 35% by weight If the Cr content is less than 11% by weight, the outdoor weather resistance and corrosion resistance are insufficient, and if it exceeds 35% by weight, the effect of improving the outdoor weather and corrosion resistance is saturated. At the same time, the moldability is reduced and it is not economical, so the content is limited to 11 to 35% by weight.

(D) Mo: 0.3 to 4% by weight Mo is an element for improving outdoor weatherability and corrosion resistance. However, if the content is less than 0.3% by weight, the effect is insufficient. 0.3 to 4% by weight is preferable since it becomes worse.

(E) Cu: 0.3 to 5% by weight Cu is an element for improving outdoor weatherability and corrosion resistance. However, if it is less than 0.3% by weight, its effect is insufficient. If it exceeds 5% by weight, its effect is saturated and hot working is performed. The content is preferably 0.3 to 5% by weight because the property is lowered.

(F) Nb: less than 1% by weight Nb is a carbide and nitride forming element and brings about an improvement in corrosion resistance and formability. However, the effect is saturated even if added in an amount of 1% by weight or more, so that it is preferably less than 1% by weight.

(G) Ti: less than 1% by weight Ti is a carbide and nitride forming element, and improves corrosion resistance and formability. However, the effect is saturated even if added at 1% by weight or more, so that less than 1% by weight is preferable.

 Next, the reasons for limiting the steps will be described.

The steel slab having the above components is subjected to ordinary hot rolling, hot-rolled sheet annealing, pickling, cold rolling with intermediate annealing, and then finish annealing.

In the present invention, when the cold-rolled steel strip manufactured as described above is subjected to finish annealing, the temperature is maintained at a temperature range of 200 to 500 ° C. for 10 seconds to 3 minutes during the temperature lowering from the annealing temperature of 950 to 1,050 ° C. By improving the strain ratio and elastic limit,
This can reduce the occurrence of pocket waves in the forming process.

If the holding temperature is less than 200 ° C. and exceeds 500 ° C., the effects are both insufficient. Therefore, the holding temperature is limited to 200 to 500 ° C.

If the holding time is less than 10 seconds, the effect is insufficient, and if the holding time is 3 minutes or more, the effect does not increase.
Limited to minutes.

In addition, after the finish annealing of the present invention, light (tempering reduction of less than 0.3%) temper rolling may be performed for shape correction.

〔Example〕

A ferritic stainless steel slab having the composition shown in Table 1 was subjected to ordinary hot rolling, hot-rolled sheet annealing, pickling, and cold rolling sandwiching intermediate annealing, followed by finish annealing of the obtained steel strip. Then, a holding process was performed during the temperature drop, and then a roll forming process was performed on the shape shown in FIG. 1, and the state of the generated pocket wave was observed.

 Note that temper rolling was performed on some steel strips.

Table 2 shows the observation results of the finish annealing temperature, the holding temperature / time, the temper rolling reduction, and the pocket wave.

According to the present invention, generation of pocket waves can be suppressed.

[Effects of the Invention] According to the present invention, a ferritic stainless steel strip having high outdoor weather resistance and corrosion resistance and capable of suppressing generation of pocket waves in the forming step can be produced.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the state of occurrence of pocket waves, and FIG. 2 is an explanatory view showing the state of occurrence of tensile deformation, compression deformation, and residual compression during roll rolling. 1 Bottom plate 2 Side plate 3 Pocket wave

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Hino 2-88 Wakihama Kaigan-dori, Chuo-ku, Kobe City, Hyogo Prefecture Inside the Hanshin Works of Kawasaki Steel Corporation (72) Inventor Masaaki Ishikawa Wakihama Beach, Chuo-ku, Kobe City, Hyogo Prefecture No. 88, Kawasaki Steel Corporation, Hanshin Works

Claims (3)

(57) [Claims] C. Less than 0.1% by weight N: Less than 0.1% by weight When finish-annealing a steel containing Cr: 11 to 35% by weight, a temperature range of 200 to 500 ° C. is applied during the temperature lowering from the annealing temperature. A method for producing a ferritic stainless steel strip, which is held for 10 seconds to 3 minutes. 2. The method for producing a ferritic stainless steel strip according to claim 1, wherein the steel according to claim 1 further contains Mo: 0.3 to 4% by weight and / or Cu: 0.3 to 5% by weight. 3. The method for producing a ferritic stainless steel strip according to claim 1, wherein the steel according to claim 1 or 2 further contains less than 1% by weight of Nb and / or less than 1% by weight of Ti.