Laser-Ultrasound-Based Grain Size Gauge for the Hot Strip Mill
Mikael Malmström, Anton Jansson, Bevis Hutchinson, Johan Lönnqvist, Lars Gillgren, Linda Bäcke, Hans Sollander, Matthias Bärwald, Sascha Hochhard, Peter Lundin
Abstract
The paper summarizes the creation of a robust online grain size gauge for a hot strip mill. A method and algorithm for calculating the grain size from the measured ultrasonic attenuation is presented. This new method is self-calibrating, does not rely on a geometrical reference sample and can cope with the effects of diffraction on the attenuation. The model is based on 52 quenched samples measured with more than 23,000 laser ultrasonics shots and has a correlation coefficient R2 of 0.8. Typical online laser ultrasonic measurements from the hot strip mill and the calculated grain size versus length are presented for a couple of steel strips.