METHOD FOR EVALUATING CLEANLINESS OF SLAB TO BECOME MATERIAL OF HIGH ENDURANCE STRENGTH STEEL AND METHOD FOR MANUFACTURING HIGH ENDURANCE STRENGTH STEEL

摘要

A method for evaluating cleanliness of a slab to become a material of a high endurance strength steel according to the present invention comprising: a classification extraction step for specifying, from information on an electron image and characteristic X rays obtained by irradiating a test piece taken from a slab with electron rays, an inclusion present in the test piece, and classifying and extracting the inclusion on the basis of a value including a total value of concentrations of Al, Ca, Mg, and Ti calculated from the information on characteristic X rays; and an evaluation step for calculating a predicted maximum diameter of the inclusion classified and extracted in the classification extraction step by using an extreme value statistical method, and evaluating cleanliness of the slab on the basis of the calculated predicted maximum diameter.