Coupled transient heat transfer—microstructure weld computations (part B)

Abstract

The Watt/Coon algorithm put forward in Part A is coupled to a transient finite element heat transfer analysis for computing the microstructure as a function of space and time ( x, y, z, t) in the heat-affected zone (HAZ) of low alloy steel welds. The input data are the composition, the thermal properties, the initial microstructure and the initial temperature of the base material, the geometry of the joint, the convective and radiative boundary conditions, and the shape and power density distribution of the heat source. Computed prior austenite grain size and residual microstructures (ferrite, pearlite. bainite, and martensite fractions) for a bead-on-plate low carbon steel weld are compared against measured values to evaluate the approach. Computer generated contour representations are presented to map microstructural fields for easy interpretation. Transient microstructural changes are included to demonstrate the capability of the system. As far as these authors know the Watt/Coon algorithm is the first model capable of predicting transient microstructural changes. Combined with FEM heat transfer analysis it is shown that this represents a very powerful system.