| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high strength martensitic stainless steel seamless pipe for an oil well having both YS of 655 MPa or more, and excellent resistance to carbon dioxide gas corrosion and sulfide stress corrosion cracking. <P>SOLUTION: The steel pipe has a composition containing, by mass%, 0.01% or less C, 0.5% or less Si, 0.1-2.0% Mn, 0.03% or less P, 0.005% or less S, more than 15.5% but 17.5% or less Cr, 2.5-5.5% Ni, 1.8-3.5% Mo, 0.3-3.5% Cu, 0.20% or less V, 0.05% or less Al, and 0.06% or less N. The steel pipe has yield strength of 655-862 MPa and tensile characteristics of 0.90 or more of yield ratio by subjecting it to quenching and tempering processes. While securing the prescribed yield strength required for the oil well application, by setting the yield ratio to 0.90 or more, the steel pipe has low tensile strength so that corrosion resistance to the carbon dioxide gas corrosion, sulfide stress corrosion cracking, and the like is improved. <P>COPYRIGHT: (C)2012,JPO&INPIT |
