Application of laser ultrasonics to the measurement of grain size

The method of measuring grain size of stainless steels at Allegheny Ludlum for application to most customer orders is the comparison method. In an effort to reduce the costs of using this method, Allegheny Ludlum is pursuing the application of automated technologies. The laser ultrasonic method appears to be the most promising. In collaboration with the National Research Council of Canada, we made preliminary measurements of the grain size of fifty-five samples of a grade of 304 stainless steel with grain sizes ranging from ASTM number of 5 to 10 and gages of 0.015 inches to 0.250 inches. The scatter in the calibration of ASTM grain size to laser ultrasonic attenuation is no worse than 1 ASTM number. This result is considered positive in light of the use of ASTM grain size numbers for the calibration.Peer reviewed: YesNRC publication: Ye