Intercritical Annealing of 22MnB5 for Hot Forming Die Quenching

Abstract

Austenitization models for ultrahigh strength steels like 22MnB5 are needed to: optimize existing furnace-based processes for hot forming die quenching (HFDQ); explore the potential of intercritical annealing to obtain softer, more ductile parts; and develop new HFDQ technologies such as direct-contact heating. This paper evaluates three such models using austenite phase fractions derived from Vickers hardness measurements made on Al-Si coated 22MnB5 coupons heated within lab-scale muffle furnace and then water-quenched. Overall, predicted trends are in good agreement with the experimental results at different soak temperatures, but experimental trends with increasing soak times are less obvious. The experimental results also highlight a deficiency in a recently-proposed physics based austenitization model at higher soak temperatures.