STEEL MATERIAL CLEANLINESS EVALUATION METHOD AND CLEANLINESS EVALUATION DEVICE

摘要

In the method for evaluating the cleanliness of steel materials according to the present invention, the inclusion detection size setting for setting the minimum length d ₃ in the width direction perpendicular to the rolling direction of the steel material, the inclusions in the steel material to be detected by ultrasonic flaw detection Step and ultrasonic inspection step of two-dimensional scanning of the steel image so that the scanning surface is parallel to the rolling direction while transmitting and receiving the ultrasonic beam to and from the steel material by means of a water immersion inspection method using the ultrasonic probe 10 that forms a point focused ultrasonic beam. And a one-dimensional processing step of acquiring a two-dimensional distribution of the ultrasonic reflection signal level corresponding to the two-dimensionally scanned surface, and one-dimensionalizing the two-dimensional distribution, and the length of the one-dimensional ultrasonic reflection signal level. and an evaluation step of obtaining and evaluating the sum of the lengths in the rolling direction of the region at a signal level equal to or greater than d ₃ .