Surface defect detection method, surface defect detection device, and steel material manufacturing method

摘要

A surface defect detection method according to the present invention is a method of optically detecting a surface defect of a steel product, and includes an irradiating step of irradiating illumination lights from different directions to an identical inspection target portion by using at least two distinguishable light sources; and a detecting step of acquiring images by reflection lights of the respective illumination lights and detecting a surface defect in the inspection target portion by performing difference processing between the acquired images. An incident angle of the illumination lights of the respective light sources are within a range of 60° to 82.5° relative to the inspection target portion.