STEEL MATERIAL EXCELLENT IN HYDROGEN INDUCED CRACK RESISTANCE AND MANUFACTURING METHOD THEREFOR

摘要

PROBLEM TO BE SOLVED: To provide a steel material excellent in hydrogen induced crack resistance, in which hydrogen induced crack resistance of the steel material can be evaluated quickly and accurately.SOLUTION: The steel material excellent in hydrogen induced crack resistance contains a predetermined amount of a chemical component such as C, Si, Mn, P, S, and Ca. The particle number of a non-metallic inclusion each having a ratio of CaO and AlO((mass% CaO)/(mass% AlO)) of 10.0 or more is 20/mmor less, the ratio of CaO and AlObeing calculated from CaO fraction (mass%) and AlOfraction (mass%), each of which is measured by a composition analysis with EDS of the non metallic inclusion having a particle diameter of 1 μm or more that is detected when 20 mmor more of a mirror polishing face of the steel sheet is observed by a scanning electron microscope is 20/mmor less.