STEEL PLATE WITH EXCELLENT HYDROGEN-INDUCED CRACKING RESISTANCE AND TOUGHNESS, AND LINE PIPE STEEL TUBE

摘要

A steel plate with excellent hydrogen-induced cracking resistance and toughness is achieved in which fine HIC of approximately several µms is also sufficiently suppressed particularly in the steel plate surface layer part which will be under a harsh environment with a high hydrogen concentration. The steel plate with excellent hydrogen-induced cracking resistance and toughness of the present invention is characterized to contain specified elements with the remainder consisting of iron and inevitable impurities, in which the ratio of Ca amount and S amount (Ca/S) is 2.0 or more, and the ratio of the maximum Ca concentration (Cmax) of a region from the surface to 5 mm depth in the plate thickness direction and the average Ca concentration (Cave) in the region (Cmax/Cave) is 1.20 or less.