| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a high-strength martensitic-stainless steel seamless pipe for an oil well, which has a YS (yield strength) of ≥655 MPa and excellent carbon dioxide corrosion resistance and sulfide stress corrosion cracking resistance. <P>SOLUTION: The steel pipe has a composition including, by mass%, ≤0.01% C, ≤0.5% Si, 0.1-2.0% Mn, ≤0.03% P, ≤0.005% S, 14.0-15.5% Cr, 5.5-7.0% Ni, 2.0-3.5% Mo, 0.3-3.5% Cu, ≤0.20% V, ≤0.05% Al, and ≤0.06% N. The steel pipe is subjected to quenching and tempering so as to have tensile properties including a yield strength of 655-862 MPa and a yield ratio of ≥0.90. The steel pipe is made to have a low tensile strength by controlling a yield ratio to ≥0.90, while maintaining a prescribed yield strength enough for an oil well, whereby the steel pipe is improved in corrosion resistance such as carbon dioxide corrosion resistance, sulfide stress corrosion cracking resistance and the like. <P>COPYRIGHT: (C)2012,JPO&INPIT |
