STEEL-PIPE SURFACE INSPECTION METHOD, SURFACE INSPECTION DEVICE, MANUFACTURING SYSTEM, DEFECT GENERATION-LOCATION SPECIFYING METHOD, AND MANUFACTURING METHOD

摘要

A control device (12) acquires a self-emission image of a steel pipe picked up when the steel pipe was hot, corrects circumferential direction uneven luminance of the self-emission image so that the luminance is uniform, and detects surface defects on the basis of the corrected self-emission image. It is preferable for the self-emission image to be picked up at a position at the rear surface of a reducer. It is preferable for a diameter reduction rate for the steel pipe, according to the reducer, to be at least 110%. Uneven luminance in the circumferential direction of the self-emission image is made uniform by using a circumferential direction luminance distribution in which the luminance in the length direction of the steel pipe is averaged. The uneven luminance in the circumferential direction of the self-emission image may be made uniform by using the differences in luminance among a plurality of self-emission images for which image pick up was performed with a position in the length direction of the steel pipe being changed.