| 摘要 |
PROBLEM TO BE SOLVED: To realize a steel pipe securely excellent in hydrogen-induced cracking resistance and toughness.SOLUTION: The steel plate has a composition comprising, by mass, 0.02 to 0.15% C, 0.02 to 0.50% Si, 0.6 to 2.0% Mn, 0.030% or lower (not including 0%) of P, 0.003% or lower (not including 0%) of S,0.010 to 0.08% Al, 0.0003 to 0.0060% Ca, 0.001 to 0.01% N, and 0.0045% or lower (not including 0%) of O (oxygen), and the balance iron with inevitable impurities, and in which the ratio between the Ca and the S is 2.0 or higher, and also the Ca, the S and the O satisfy (Ca-1.25S)/O≤1.80, and further, the content of an Ar gas in the steel is 0.5 μL/cmor lower. |
