Patent ID: 7931757

Claim:
A seamless steel pipe for line pipe characterized by having a chemical composition which consisting essentially, in mass percent, of C: 0.02-0.08%, Si: at most 0.5%, Mn: 2.02-3.0%, Al: 0.001-0.10%, Mo: greater than 0.4%-1.2%, N: 0.002-0.015%, at least one of Ca and REM in a total amount of 0.0002-0.007%, Cr: 0-1.0%, Ti: 0-0.05%, Ni: 0-2.0%, Nb: 0-0.04%, V: 0-0.2%, Cu: 0-1.5%, B: 0-0.01%, Mg: 0-0.007%, and a remainder of Fe and impurities, with the impurities having the content of P: at most 0.05%, S: at most 0.005%, and O: at most 0.005%, and the chemical composition satisfying the following inequality: 1.1≦[Mn]×[Mo]≦2.6, wherein [Mn] and [Mo] are the numbers equivalent to the contents of Mn and Mo, respectively, in mass percent.