PROCESS FOR PRODUCTION OF DUPLEX STAINLESS STEEL PIPE

WIPO Patent Application WO/2010/082395

A1

A process for the production of a duplex stainless steel pipe having a minimum yield strength of 758.3 to 965.2MPa, which comprises: subjecting a duplex stainless steel material having a chemical composition that contains by mass C: 0.03% or less, Si: 1% or less, Mn: 0.1 to 4%, Cr: 20 to 35%, Ni: 3 to 10%, Mo: 0 to 6%, W: 0 to 6%, Cu: 0 to 3%, N: 0.15 to 0.60% with the balance being Fe and impurities to hot working either alone or followed by solution treatment to produce a pipe stock for cold working; and then cold-rolling the pipe stock into a duplex stainless steel pipe, characterized in that the cold rolling is conducted under such conditions that the reduction ratio (Rd) (in terms of reduction in area) in the final cold rolling step falls within the range of 10 to 80% and satisfies the relationship (1): Rd=exp[{ln(MYS)-ln(14.5×Cr+48.3×Mo+20.7×W+6.9×N)}/0.195]∙∙∙(1) wherein Rd and MYS represent reduction ratio (%) (in terms of reduction in area) and desired yield strength (MPa) respectively; and Cr, Mo, W, and N represent their respective contents (mass%).

SUWABE, Hitoshi (5-33, Kitahama 4-chome, Chuo-ku, Osaka-sh, Osaka 41, 〒5410041, JP)
諏訪部　均 (〒41 大阪府大阪市中央区北浜四丁目５番３３号　住友金属工業株式会社内 Osaka, 〒5410041, JP)

JP2009/068743

July 22, 2010

November 02, 2009

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SUMITOMO METAL INDUSTRIES, LTD. (5-33, Kitahama 4-chome Chuo-ku, Osaka-sh, Osaka 41, 〒5410041, JP)
住友金属工業株式会社 (〒41 大阪府大阪市中央区北浜四丁目５番３３号 Osaka, 〒5410041, JP)
SUWABE, Hitoshi (5-33, Kitahama 4-chome, Chuo-ku, Osaka-sh, Osaka 41, 〒5410041, JP)

C21D8/10; B21B21/00; B21C1/22; B21C23/08; C22C38/00; C22C38/58

SUGIOKA, Kanji et al. (K. SUGIOKA PATENT OFFICE, 2-5-10 Sonezaki, Kita-ku, Osaka-sh, Osaka 57, 〒5300057, JP)

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