Patent ID: 8317946

Claim:
A seamless low-alloy steel pipe comprising, in percent by mass, C: 0.10 to 0.18%, Si: 0.05 to 1.0%, Mn: 0.05 to 1.2%, Ni: 0.05 to 1.5%, Cr: 0.50 to 1.50%, Mo: 0.50 to 1.50%, Nb: 0.002 to 0.10%, Al: 0.005 to 0.10%, and either or both of Ti: 0.003 to 0.050% and V: 0.01 to 0.20%, the balance being Fe and impurities, the impurities containing 0.025% or less of P, 0.005% or less of S, 0.007% or less of N, and less than 0.0003% of B, wherein a wall thickness of the pipe is 20 mm or more, the tensile strength is 950 MPa or more and the yield strength is 850 MPa or more, and the Charpy absorbed energy at −40° C. is 60 J or more.