| 摘要 |
PURPOSE:To provide the titled two-phase stainless steel excellent in stress corrosion cracking resistance and pitting resistance in a corrosive environment, by prescribing the contents of C, Si, Mn, Cr, Ni, Mo, Cu and Co and providing a delta- ferrite phase with a specific areal ratio. CONSTITUTION:The titled two-phase stainless steel consists of, on a wt. basis, 0.08% or less C, 0.2-2.0% Si, 0.2-2.0% Mn, 19.0- less than 24.0% Cr, 4.0- 10.0% Ni, 1.0-5.0% Mo, 0.5-3.0% Cu, 0.2-4.0% Co and the remainder of substantially Fe. In this case, the areal ratio of the delta-ferrite phase in the metal structure of this stainless steel is set to be 30-70% as a prerequsite condition. This stainless steel is excellent in pitting resistance, stress corrosion cracking resistance and hydrogen sulfide craking resistance and has high strength and high ductility in a corrosive environment, especially, in an environment containing chloride, CO2 or H2S, for example, under a high temp. and high pressure condition of 300 deg.C and 6,000psi.
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