| 摘要 |
This invention provides a high-strength steel material for an oil well, excellent in strength and SSC resistance, and having a yield strength of at least 120 ksi. The steel material contains C: 0.10 to 0.40%, Si </= 0.5%, Mn </= 0.5%, P </= 0.015%, S </= 0.0050%, Mo: 0.5 to 2.5%, A1: 0.005 to 0.1%, Ti: 0.005 to 0.1% and at least 3.4 times N, Nb: 0.01 to 0.1%, N </= 0.01% and B: 0.0005 to 0.0050%, wherein the yield strength expressed by ksi and the Mo content satisfy the following relation (1), the balance of the C, Mn and Mo contents satisfies the following relation (2), and the steel material may contain, whenever necessary, at least one of Cr </= 0.2%, W </= 0.5%, V: 0.01 to 0.3%, Zr: 0.001 to 0.01%, Ca: 0.001 to 0.01%, Mg: 0.001 to 0.01% and REM: 0.001 to 0.01%. <DF NUM="(1)"> alpha = Mo - 0.15YS >/= -18.9 </DF> <DF NUM="(2)"> beta = 2.7C + Mn + 2Mo >/= 2.0 </DF> <IMAGE> |
