Finite element simulation of quench distortion in a low-alloy steel incorporating transformation kinetics

The uncontrolled distortion of steel parts has been a long-standing and serious problem for heat treatment processes, especially quenching. To get a better understanding of distortion, the relationship between transformation kinetics and associated distortion has been investigated using a low-alloy chromium steel. Because martensite is a major phase transformed during the quenching of steel parts and is influential in the distortion, a new martensite start (M_s) temperature and a martensite kinetics equation are proposed. Oil quenching experiments with an asymmetrically cut cylinder were conducted to confirm the effect of phase transformations on distortion. ABAQUS and its user-defined subroutines UMAT and UMATHT were used for finite element method (FEM) analysis. The predictions of the FEM simulation compare well with the measured data. The simulation results allow for a clear understanding of the relationship between the transformation kinetics and distortion.