Electromagnetic sensors for in-situ dynamic microstructure monitoring of recovery and recrystallisation in interstitial free steels
Lei Zhou, Fanfu Wu, Russell Hall, Claire Davis
Abstract
An in-situ high temperature EM sensor was used to detect changes in the microstructural state caused by recovery and recrystallisation for IF steel samples during heat treatment. The relative permeability values determined from the sensor measurements at the different heat treatment temperatures showed the expected strong influence of temperature on the magnetic measurement. The relative permeability values determined at each temperature increased during the recovery and recrystallisation processes and correlated well with the different microstructural states determined by EBSD. The results show that the EM sensor measurement approach shows significant potential for in-situ microstructure monitoring during the annealing process of IF steels, with larger magnetic parameter changes between microstructural states at the higher temperatures typical of commercial annealing practice. In addition it is seen that the magnetic, and EM sensor, measurements show more sensitivity to recovery than hardness measurements, and can also monitor recrystallisation.