Manufacturing method of steel using the same steel and non-metallic inclusions inspection method

摘要

PPROBLEM TO BE SOLVED: To provide an inspection method for inspecting a nonmetal inclusion in steel with high precision, and to provide a manufacturing method of steel material using it. PSOLUTION: In the inspection method of the nonmetal inclusion in steel, the surface of steel subjected to mirror surface polishing is observed using an optical microscope using a single wavelength laser beam source as an illumination light source and the nonmetal inclusion is discriminated on the basis of the brightness difference between steel and the nonmetal inclusion in the observed variable density image. Further, in the manufacturing method of the steel material, the cleanness of a steel cast piece and/or the steel material is investigated by adapting the inspection method of the nonmetal inclusion in steel and a manufacturing condition is adjusted and/or the steel material is classified on the basis of the investigation result to manufacture the steel material coinciding with required cleanness. PCOPYRIGHT: (C)2007,JPO&INPIT