A new technique for the quantitative real-time monitoring of austenite grain growth in steel

A new technique to measure quantitatively grain growth kinetics at high temperatures was presented in this article. This technique, based on the generation and detection of ultrasound using lasers, called laser-ultrasonics, measures the scattering of ultrasonic echoes propagating in a sample to evaluate grain size. A quantitative evaluation was obtained by comparing ultrasonic attenuation with quantitative metallographic size measurements of austenite grains. Results obtained using this new technique during the austentization of A36, drawing quality special killed (DQSK), and interstitial free (IF) steel samples were presented. The results presented showed that this new technique provides the austenite grain growth kinetics at a given austenization temperature in a single experiment with a time resolution far superior to the resolution obtained using lengthy conventional metallographic techniques. This new technique measures the average microstructure in the bulk and requires little or no sample preparation. Furthermore, measurements in DQSK and IF steel samples were presented whereas conventional metallographic techniques cannot be used easily with low-carbon steels and not at all with IF steel.