Study of recrystallisation in interstitial free (IF) steel by ultrasonic measurements

Abstract

The purpose of understanding recrystallisation in interstitial free (IF) steel through non-destructive ultrasonic measurements was to develop an online system to monitor specific grain conditions, textures and mechanical properties during annealing of such steels. Ultrasonic measurements for microstructure and property evaluation samples had larger volumes of the material when compared with other conventional methods. In order to make it an alternative to the conventional destructive methods using microscopes, X-ray diffraction, mechanical testing, hardness testing, etc., correlation between the ultrasonic surface wave velocities in 45° to rolling direction and average velocity v-Bar and those of materials parameters like plastic strain ratio r-Bar, hardness, texture, in cold rolled IF steel sheets with 79% thickness reduction and annealed at 650°C for different soaking times were developed. The ultrasonic surface wave velocity measurements at 45° to rolling direction and average velocity v-Bar were found to be the ultrasonic parameters to be monitored to control recrystallisation in IF steels.