Computation of isothermal transformation diagrams of 42CrMo4 steel from dilatometer measurements with continuous cooling

Abstract

AbstractTo generally predict the mechanical properties of steels following heat treatment, the isothermal time–temperature–transformation (TTT) diagrams must be known. The isothermal kinetics of the phase transformation is influenced by the austenitisation conditions and the deformation processes. Owing to the requirements of the process chain 'integrated heat treatment following hot-forging', the steels are austenitised at a comparatively high temperature and deformed before quenching. The TTT diagrams found in the literature only treat limited austenitisation temperatures and do not generally consider different deformation levels. However, the measurements of the corresponding TTT diagrams are both costly and time consuming. In addition to this, the isothermal transformations of low alloyed steels, which transform very quickly, cannot be measured using those dilatometers which are readily available.1 In this paper, the TTT diagrams of the 42CrMo4 steel austenitised at 1200°C and deformed at different le...