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1. (WO2009119895) LOW-ALLOY DUPLEX STAINLESS STEEL WHEREIN WELD HEAT-AFFECTED ZONES HAVE GOOD CORROSION RESISTANCE AND TOUGHNESS

Pub. No.:    WO/2009/119895    International Application No.:    PCT/JP2009/056840
Publication Date: Oct 1, 2009 International Filing Date: Mar 26, 2009
IPC: C22C 38/00
C22C 38/58
Applicants: Nippon Steel & Sumikin Stainless Steel Corporation
新日鐵住金ステンレス株式会社
OIKAWA, Yuusuke
及川雄介
URASHIMA, Hiroshi
浦島裕史
TSUGE, Shinji
柘植信二
INOUE, Hiroshige
井上裕滋
MATSUHASHI, Ryo
松橋亮
Inventors: OIKAWA, Yuusuke
及川雄介
URASHIMA, Hiroshi
浦島裕史
TSUGE, Shinji
柘植信二
INOUE, Hiroshige
井上裕滋
MATSUHASHI, Ryo
松橋亮
Title: LOW-ALLOY DUPLEX STAINLESS STEEL WHEREIN WELD HEAT-AFFECTED ZONES HAVE GOOD CORROSION RESISTANCE AND TOUGHNESS
Abstract:
Provided is a low-alloy duplex stainless steel that can inhibit loss of corrosion resistance and toughness in weld heat-affected zones. The steel is characterized by containing, by mass, no more than 0.06% carbon, between 0.1% and 1.5% silicon, between 2.0% and 4.0% manganese, no more than 0.05% phosphorus, no more than 0.005% sulfur, between 19.0% and 23.0% chromium, between 1.00% and 4.0% nickel, no more than 1.0% molybdenum, between 0.1% and 3.0% copper, between 0.05% and 0.5% vanadium, between 0.003% and 0.050% aluminum, no more than 0.007% oxygen, between 0.10% and 0.25% nitrogen, and no more than 0.05% titanium, with the remainder comprising iron and unavoidable impurities. The steel is further characterized in that the variable Md30 given by formula (1) is less than or equal to 80, the variable Ni-bal given by formula (2) is between −8 and −4 inclusive, Ni-bal and the amount of nitrogen included fulfill formula (3), the austenite phase area ratio is between 40% and 70%, and twice the mass% of nickel plus the mass% of copper is at least 3.5%. (1): Md30 = 551 − 462×(C+N) − 9.2×Si − 8.1×Mn − 29×(Ni+Cu) − 13.7×Cr − 18.5×Mo − 68×Nb (2): Ni-bal = (Ni + 0.5Mn + 0.5Cu + 30C + 30N) − 1.1 (Cr + 1.5Si + Mo + W) + 8.2 (3): N (%) ≤ 0.37 + 0.03×(Ni-bal)