Microstructure evolution model for the HAZ of girth welds in X80 linepipe steel

A phenomenological model has been developed to describe austenite grain growth, precipitate dissolution and austenite decomposition into ferrite, bainite and martensite/austenite (MA) constituents for an X80 linepipe steel. The predictive capabilities of the integrated model for the heat affected zone (HAZ) have been validated with laboratory simulations of heat treatment cycles for selected positions in the HAZ. The model predicts the fraction of transformation products as a function of distance from the fusion line. To connect the microstructure model to a mechanical property model for the HAZ it will be required to incorporate a module on MA island size as this is expected to critically affect the fracture toughness. (AU) Copyright © 2013 Companhia Brasileira de Metalurgia e Mineração (CBMM) All Rights Reserved