HYDROGEN ENBLITTLEMENT SENSITIVITY EVALUATION METHOD OF STEEL PRODUCT AND STEEL PRODUCT HAVING EXCELLENT HYDROGEN ENBLITTLEMENT RESISTANCE

摘要

PROBLEM TO BE SOLVED: To provide a method capable of executing quick and highly sensitive evaluation of hydrogen embrittlement sensitivity relative to various steel products including a plated steel sheet, and a steel product having excellent hydrogen embrittlement resistance. SOLUTION: Correlation between the quantity of diffused hydrogen existing in a steel and a hydrogen embrittlement risk index H(%) obtained by the undermentiotted equation by a low distortion speed tensile test with a distortion speed below 110-4/sec is obtained beforehand relative to the same kind of steel product as a steel product which is an evaluation object. The quantity of diffused hydrogen existing in the steel of the steel product which is the evaluation object is measured, and a hydrogen embrittlement risk of the steel product is evaluated from the correlation based on the measured diffused hydrogen quantity. In the case of a plated steel sheet, anode electrolysis of a plating coat is preferably executed in alkali solution with pH of 10 or more before measurement of the diffused hydrogen quantity to dissolve and remove the coat. In the undermentioned equation, E0 is an elongation at the breaking time of a test piece of a steel product including substantially no diffusible hydrogen in the steel, and E1 is an elongation at the breaking time of a test piece of a steel product including diffused hydrogen in the steel. H(%)=100(1-E1/E0).