Materials Modelling for Selective Heating and Press Hardening of Boron Steel Panels with Graded Microstructures

Abstract

In order to model a novel and complete hot stamping process for forming boron steel panels with graded microstructures, three sets of physically-based material models have been introduced. They are an austenite transformation model for boron steel under selective heating, a viscoplastic-damage constitutive model and a martensite and bainite transformation model for boron steel under press hardening conditions. Material constants are given, determined from the results of fundamental experiments. In addition, the determined unified constitutive equations have been embedded in the commercial Finite Element code LS-DYNA via user defined subroutines, where the three sets of models are integrated through internal state variables. An FE process simulation model and numerical procedure have been established and are illustrated.