Development of measurement technology of phase transformation ratio on steel plates using laser-ultrasound

This paper describes a non-contact scheme for laser-ultrasound measurement incorporating a Q-switched Nd:YAG laser as an ultrasonic generation source and a confocal Fabry-Perot interferometer with a single-frequency long pulsed laser for ultrasonic detection. Measurement in laboratory environment is firstly performed. In the experiment, the ultrasound measurement is conducted on a steel plate in order to obtain a relationship between ultrasonic velocity and ratio of phase transformation from austenite to ferrite which is an important parameter to determine the quality of steel products. Experimental results show that the ultrasonic velocity changes with the phase transformation ratio. A pilot plant test is also tried to verify the possibility of application to a real production line.