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Ferritic-austenitic stainless steel excellent in corrosion resistance and workability and method of production of same

a technology of austenitic stainless steel and corrosion resistance, which is applied in the field of ferric-austenitic stainless steel, can solve the problems of poor corrosion resistance low workability of ferritic stainless steel, and low workability of ferritic stainless steel, and achieves excellent corrosion resistance and high “uniform elongation”

Inactive Publication Date: 2013-05-16
NIPPON STEEL CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention relates to a new type of ferritic-austenitic stainless steel with excellent corrosion resistance and workability. By controlling the metal structure and annealing conditions, this steel has a corrosion resistance and uniform elongation that is equal to or greater than SUS 304. Additionally, this steel has a high pitting potential, indicating its ability to resist corrosion under specific circumstances. The technical effects of the invention are its ability to offer a high-quality, corrosion-resistant and workable stainless steel option.

Problems solved by technology

Ferritic stainless steel contains almost no Ni and generally has considerably lower workability than austenitic stainless steel.
However, ferritic stainless steel is very inferior to austenitic stainless steel with respect to workability, particularly in material elongation and uniform elongation.
Further, it contains several percent of Mo—which is rarer and more expensive than Ni.
Therefore, there is still a problem in terms of spread of use and economy.
However, if the uniform elongation does not increase, the actual workability will not improve.
Further, even if steel sheet or plate does not break and “fracture” in actual shaping, it is often judged unworkable when necking occurs.
However, even these citations do not describe at all the uniform elongation which governs the actual workability.

Method used

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  • Ferritic-austenitic stainless steel excellent in corrosion resistance and workability and method of production of same
  • Ferritic-austenitic stainless steel excellent in corrosion resistance and workability and method of production of same
  • Ferritic-austenitic stainless steel excellent in corrosion resistance and workability and method of production of same

Examples

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example 1

[0146]Ferritic-austenitic stainless steel 250 mm thick cast slabs if the ingredients shown in Table 2 were produced and hot rolled into hot rolled steel plates with 5.0 mm plate thicknesses. Steel No. 1 to Steel No. 20 have ingredients defined in the present invention. Steel No. 21 to 26 have ingredients deviating from the definitions in the present invention. These hot rolled steel plates were annealed and pickled, then cold rolled to 1 mm thicknesses and final annealed. The final annealing was also performed under conditions deviating from the definitions of the present invention for comparison.

[0147]Various test pieces were taken from each of the obtained cold rolled and annealed sheets and evaluated for the γ phase volume fraction (γ fraction), pitting potential, and uniform elongation. The γ fraction was found by the EBSP method described in paragraph 0046. For the pitting potential, the V′c100 (Vv.s.AGCL) was measured for a #500 polished surface in a 30° C., 3.5% NaCl aqueous ...

example 2

[0152]Next, examples according to the second findings will be shown.

[0153]The steels shown in Table 4 were produced, then were hot rolled, then the hot rolled plates were annealed, cold rolled, and final annealed to produce 1.0 mm thick thin-gauge steel sheets. In producing the steel sheets, the metal structure can be changed by changing the material thickness, heating temperature of hot rolling, rolling pass schedule, rolling pass time, hot rolled sheet annealing temperature, and final annealing temperature and time. However, this time, the final annealing temperature was changed, and the annealing time was made 60 seconds. The obtained product sheets were subjected to tensile tests and the uniform elongation was measured. Further, from the metal structure of the thin-gauge steel sheet / L cross-section, the phases were identified by EBSP, the grain size and shape aspect ratio were investigated, and the distance between nearest grains of the austenite grains was measured. The conditi...

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Abstract

The present invention relates to ferritic-austenitic stainless steel oriented to have low Ni which is excellent in corrosion resistance, particularly in corrosion resistance in a neutral chloride environment, and has high “uniform elongation”—a factor governing workability—and a method of production for the same.There are independently provided ferritic-austenitic stainless steels and methods of production for the same particularly having a corrosion resistance in a neutral chloride environment satisfyingPI value(=Cr+3Mo+10N−Mn)≧18% and having a uniform elongation satisfying−10≦Md≦110 (where Md=551−462({C}+[N])−9.2[Si]−8.1[Mn]−13.7[Cr]−29[Ni]−29[Cu]−18.5[Mo], where [ ] is composition (mass %) in the austenite phase, and { } is average composition (mass %))

Description

TECHNICAL FIELD[0001]The present invention relates to ferritic-austenitic stainless steel excellent in corrosion resistance and workability and a method of production of the same. According to the present invention, it is possible to produce ferritic-austenitic stainless steel excellent in corrosion resistance and workability without including a large amount of the expensive and rare element of Ni, so it is believed this can contribute to resource conservation and environmental protection.BACKGROUND ART[0002]Stainless steel may be broadly divided into austenitic stainless steel, ferritic stainless steel, and two-phase (ferritic-austenitic) stainless steel. Austenitic stainless steel contains expensive Ni in 7% mass or more. Many types are excellent in workability. Ferritic stainless steel contains almost no Ni and generally has considerably lower workability than austenitic stainless steel. On the other hand, two-phase (ferritic-austenitic) stainless steel has a comparatively small ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C22C38/42C22C38/50C22C38/44C22C38/48C21D8/00C22C38/58
CPCC21D6/004C21D6/005C21D8/0226C21D8/0236C21D8/0263C22C38/58C21D2211/005C22C38/001C22C38/18C22C38/42C21D2211/001
Inventor HATANO, MASAHARUTAKAHASHI, AKIHIKOISHIMARU, EIICHIROKIMURA, KEN
Owner NIPPON STEEL CORP
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