Tempering behavior of industrially made DP980 steel and laboratory-made DP steels and its impact on magnetic properties

Abstract

In this study hot-rolled (HR) 2.8 mm thick DP980 steel was water quenched (WQ) in laboratory from various temperatures to simulate welding-induced microstructures. The HR and WQ (925◦C) samples were tempered in the temperature range 200–600◦C to study the temper-induced changes in microstructure, mechanical properties, and their correlation with the magnetic properties. Microhardness, yield strength, and ultimate tensile strength of the steels were increased along with the coercivity while ductility, remanence and maximum inductions were decreased with increase in austenitization temperature for the enhancement of martensites. A reversing trend in the above properties was found with increase in tempering temperature due to the softening of the steel. However, the decreases in the properties were higher at the higher tempering temperatures in WQ samples compared to the HR samples for the stress relaxation in the steel due to reduction in density of dislocations produced during water quenching and softening of martensites.