Phase transformations in a boron-alloyed steel at high heating rates

Abstract

Products or semi-finished products featuring tailored properties are highly relevant for many industrial applications. Hence, new technologies that allow to locally adapt mechanical properties are of key interest. For example, tailoring properties in profiles or tubes by a local heat-treatment appear to be promising in combination with subsequent forming operations requiring locally adapted material strength to realize complex shapes. To implement an inline process of tube forming and local heat treatment by inductive heating and spray quenching, dilatometric investigations were carried out for a heat treatable boron-alloyed steel 1.5528 (22MnB5). In particular, focus was on the effect of high inductive heating rates on the austenite formation. The influence of heating rates in the range from 500 K/s to 2500 K/s on the austenitization was evaluated and a continuous time-temperature-austenitization diagram proposed. The results can be used to compute the decomposition of ferrite and pearlite due to inductive heating.