A Simplified Model For Heat Treatment Simulation

Abstract

This work presents a simplified model to predict strain and stresses produced
during heat treatment of ferrous alloys, using the finite element method. From a
computational point of view, this problem requires coupled thermal-metallurgicalmechanical
analysis, modeled as non-stationary and nonlinear processes. Calculation of
metallurgical properties is coupled directly with thermal analysis, because thermal properties
depend on microstructural composition. Metallurgical transformations occurring during the
process are important in the development of internal stresses and distortions, because they
change mechanical properties of the metal, but also involve specific volume changes that are
coupled to thermal dilatations. The microstructures formed during heat treatment depend on
alloy composition, temperatures and cooling rate, as can be observed in TTT or CCT
diagrams. For a given material, their properties could be considered as functions of
temperature and microstructural composition and, in a second analysis, as functions of
temperature and time. Taking into account the difficulties to obtain material parameters to
model accurately their properties with more sophisticated models, a piecewise linear model is
proposed. A numerical example applied to a real case is presented.