JPH02310321A - Production of ferritic stainless steel strip - Google Patents

Abstract

PURPOSE:To obtain the steel strip having high outdoor weatherability and corrosion resistance and reduced in the occurrence of pocket wave in a forming stage by subjecting a steel having limited Cr content to finish annealing in a cold rolling stage, carrying out bending at a prescribed temp. for a prescribed length of time, and controlling the amount of surface strain of a steel strip. CONSTITUTION:A slab of a ferritic stainless steel containing 11-35wt.% Cr is subjected to ordinary hot rolling, hot rolled plate annealing, pickling, cold rollings in which process annealing is performed between the cold rolling stages, and finish annealing and is then subjected to bending at 150-550 deg.C for 5-60sec by the use of a leveler, etc., by which the amount of surface strain of the steel strip is regulated to 0.05-0.5%.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a method for manufacturing an exterior building material, particularly a ferritic stainless steel strip that is formed into a thin plate and used as a roofing material.

[Conventional technology 1] Stainless steel sheets were often used as exterior building materials in relatively small areas such as sash, curtain walls, and panels. 3 However, in recent years, stainless steel's excellent corrosion resistance and weather resistance have been recognized. Furthermore, along with the development of construction techniques, it has come to be used as a roofing material.

In this case, the roofing material is a painted stainless steel plate that is made of a stainless steel plate and is colored with paint. This is an attempt to overcome the drawback that with conventional tin roofs, if a defect occurs in the coating due to deterioration of the coating film, the roof will become unusable due to leakage due to holes in a short period of time.

This coated stainless steel plate is mainly made of 5US304 (18Cr-8N), which is an austenitic stainless steel.
i) has been adopted because of its good workability.

However, with the above-mentioned painted stainless steel sheets, it is unclear from the appearance whether the underlying material is stainless steel because of the coating film, and the disadvantage is that the beauty and luxury of the stainless steel surface cannot be taken advantage of. There was a problem that it required Furthermore, since austenitic stainless steel contains a large amount of expensive Ni, its price is high, making it difficult to increase demand.

However, when unpainted ferritic stainless steel is used as an exterior building material, especially as a roofing material, it must have sufficient outdoor weather resistance and corrosion resistance such as red rust or pitting due to the adhesion of sea salt particles for a period of 10 years or more. Corrosion resistance is inevitably required.

In addition, with austenitic stainless steel, it was relatively easy to work, so it was relatively non-problematic, but with ferritic stainless steel, for example, as shown in Figure 1, the bottom plate and side plates are easily formed during forming into roofing materials. Pocket waves (also called oil cans), which are uneven surfaces, tend to appear, and this phenomenon is a problem because it impairs the appearance of the roof.

[Problem to be Solved by the Invention J] The present invention uses a ferritic stainless steel strip produced in a cold rolling process as a roofing material, etc. without painting, so it has sufficient outdoor weather resistance and corrosion resistance, and It is an object of the present invention to provide a method for producing a ferritic stainless steel strip having good workability and capable of being formed without pocket wave phenomenon.

[Means to solve the problem] The present invention aims to solve the above problems.

After finish annealing the ferritic stainless steel containing 11 to 35% by weight of Cr in the cold rolling process, bending was performed at 150 to 550°C for 5 to 60 seconds to reduce the surface strain of the j14 band to 0.05 to 0.05. 0.
5% of ferritic stainless steel strip.

[Operation J Generally, ferritic stainless steel strips are hot rolled, then annealed and pickled, then cold rolled two or more times with - or intermediate annealing, and then finished annealed and temper rolled to produce a product. It is said that

As a result of various studies on the deformation shown in FIG. 2 that occurs during the forming process of stainless steel strips, the present inventors found that
The present invention was achieved by obtaining the following knowledge.

(1) Among the mechanical properties of the stainless steel sheet, increase the strain ratio ([tensile direction strain]/[width direction strain] in the C direction tensile test, hereinafter simply referred to as strain ratio) in the steel strip C direction slight deformation region. Then, the residual tensile stress in the bent portion becomes small, the bottom plate compressive stress becomes small, and as a result, pocket waves are reduced.

(2) When the C-direction elastic limit of the steel strip is increased, the deformation region of the bent portion becomes smaller and the compressive stress of the bottom plate becomes smaller, resulting in fewer pocket waves.

That is, in order to achieve the purpose of the present invention.

It has outdoor weather resistance and corrosion resistance, and the strain ratio is large.
There is a need to produce a ferritic stainless steel strip with a high elastic limit.

In the present invention, a ferritic stainless steel containing 11 to 35% by weight of Cr is used.
If it is less than 1% by weight, outdoor weather resistance and corrosion resistance are insufficient.
If it exceeds 35%, the effect of improving outdoor weather resistance and corrosion resistance will be saturated, and the moldability will decrease, making it uneconomical, so it was limited to 11 to 35% by weight.

In addition to the above-mentioned Cr, the ferritic stainless steel used in the present invention contains 0.3 to 4% by weight of MOj15 and/or 0.3% by weight to improve outdoor weather resistance and corrosion resistance.
In addition to 3 to 5% by weight of Cu, each wire may further contain 1% by weight or less of Nb and/or 1% by weight or less of Ti in order to improve formability.

Steel slabs with the above components can be produced by normal hot rolling, hot rolled plate annealing,
Cold rolling with pickling and intermediate annealing.

After finishing annealing, bending is performed for 5 to 60 seconds at 150 to 550°C to reduce the surface strain of the steel strip by 0.05 to 0.5%.
shall be.

Bending can be carried out using a leveler, for example.
The amount of surface strain in the i4 band is determined by thin film X-ray diffraction (l l l)
It is determined from the half value of the diffraction curve in the plane <112> direction.

In bending, if the processing temperature is less than 150°C, the effect is insufficient, if it exceeds 550°C, carbonitride precipitation may occur and it is unsuitable, and if the processing time is less than 5 seconds, the effect is insufficient; The effect becomes saturated when exceeding
．． If it is less than 0.5%, the effect is insufficient; if it exceeds 0.5%, the shape of the plate deteriorates and becomes unsuitable; if any one of the processing temperature, processing time, or amount of surface strain deviates from the above-mentioned limited range, the effect is insufficient. Pocket wave resistance cannot be obtained.

〔Example〕

A ferritic stainless steel slab having the composition shown in Table 1 was cold-rolled to a thickness of 0.8 mm by performing normal hot rolling, hot-rolled plate annealing, pickling, and intermediate annealing. These steel plates were finished annealed for 1,000°C, and then bent using a warm leveler to form steel strips. These steel strips were then pickled and adjusted at a rolling reduction rate of 1%. After passing through rolling, roll forming was performed into the shape shown in FIG.

Temperature, time and amount of surface strain in warm leveler treatment,
Formability of the obtained steel strip (C-direction strain ratio, C-direction elastic limit), pocket wave resistance during forming (crest height,
Judgment) are shown in Table 1.

[Effects of the Invention J According to the present invention, it was possible to produce a ferritic stainless steel strip that has high outdoor weather resistance and corrosion resistance, and generates fewer pocket waves during the forming process.6

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram showing how pocket waves are generated, and Figure 2 is a diagram showing tensile deformation during roll rolling. FIG. 3 is an explanatory diagram showing the state of occurrence of compressive deformation and residual compression. l...Bottom plate 2-side plate 3...Pocket wave

Claims (1)

[Claims] 1 After finish annealing a ferritic stainless steel containing 11 to 35% by weight of Cr in a cold rolling process, the surface of the steel strip is bent at 150 to 550°C for 5 to 60 seconds. A method for manufacturing a ferritic stainless steel strip, characterized in that the amount of strain is 0.05 to 0.5%.