Method for evaluating the resistance to hydrogen cracking of steel materials and steel sheets for high strength sour line pipes with good resistance to hydrogen cracking

摘要

PROBLEM TO BE SOLVED: To provide a method for evaluating and determining the HIC crack sensitivity of a slab and a steel plate by measuring an Mn concentration distribution and taking the influence of content and a segregation degree into consideration.SOLUTION: A method evaluates anti-hydrogen crack sensitivity of a steel plate by using all Q values measured and calculated in each basic measurement area defined by the following expression (1) composed of the element content of a steel material and an Mn segregation degree of a central segregation part. Q=Cf+Cf/6+(Cf+Cf+Cf)/5+(Cf+Cf)/15+Cf/4+2Cf....expression (1). In this case, f represents an Mn segregation degree in a segregation part, and a value defined by (C/C), Crepresents Mn concentration obtained by measuring an Mn concentration distribution of the central segregation part with a cross section of the steel material in a width direction, Crepresents average concentration of Mn concentration, N of frepresents an exponentiation, and Crepresents the content (mass%) of an element i, respectively.