HIGH STRENGTH STEEL PIPE HAVING STRENGTH HIGHER THAN THAT OF API X65 GRADE

摘要

A high strength steel pipe having a strength higher than that of API X65 grade,which has a chemical composition,in mass %:C:0.02 to 0.08 %,Si:0.01 to 0.5 %,Mn:0.5 to 1.8 %,P:0.01 % or less,S:0.002 % or less,Al:0.01 to 0.07 %,Ti:0.005 to 0.04 %,Mo:0.05 to 0.50 %,at least on element selected from between Nb:0.005 to 0.05 and V:0.005 to 0.10 %,and balance:Fe,and a structure wherein a ferrite phase accounts for 90 vol % or more,and a composite carbide containing at least one element selected from among Ti,Mo,and Nb,V is deposited in the ferrite phase.The high strength steel pipe is excellent in the resistance to HIC and the toughness after welding,and also can be produced with stability at a low cost.