| 摘要 |
Provided is a low alloy steel pipe for an oil well, the steel pipe having high strength and stably exhibiting excellent SSC resistance. The low alloy steel pipe for an oil well has a chemical composition that contains not less than 0.15% but less than 0.30% of C, 0.05-1.00% of Si, 0.05-1.00% of Mn, not more than 0.030% of P, not more than 0.0050% of S, 0.005-0.100% of Al, not more than 0.005% of O, not more than 0.007% of N, not less than 0.10% but less than 1.00% of Cr, more than 1.0% but not more than 2.5% of Mo, 0.01-0.30% of V, 0.002-0.009% of Ti, 0-0.050% of Nb, 0-0.0050% of B, and 0-0.0050% of Ca, with the remainder consisting of Fe and impurities. The chemical composition satisfies Mo/Cr = 2.0, has a crystal grain size number of 7.0 or higher, contains 50 or more cementite grains having circle-equivalent diameters of 200 nm or greater per 100 µm2 of matrix, has a number density of M2C type alloy carbides of 25 per µm2 or higher, and has a yield strength of 758 MPa or higher. |
