Microstructural development in an HSLA80 laser beam weldment

Abstract

The microstructures in a laser beam weld of an HSLA80 steel were determined by point counting. The prior austenite grain size of the weldment was also measured using an hexagonal model of the epitaxial grains. Based on the fusion zone boundary, laser power, welding speed, laser spot size, and efficiency, the temperature profiles of the weldment were determined using a two parameter heat flow model of laser beam welding. The thermal profiles from die center of the weldment, the chemistry of the base plate, and the prior austenite grain boundary were inputted into a thermodynamically based, empirical, computer model of the microstructural development of a weldment. A comparison of the experimental data and the computer calculation showed good agreement, but some differences. Both the agreement and the differences are discussed in terms of published continuous cooling curves for HSLA80 steels.The microstructures in a laser beam weld of an HSLA80 steel were determined by point counting. The prior austenite grain size of the weldment was also measured using an hexagonal model of the epitaxial grains. Based on the fusion zone boundary, laser power, welding speed, laser spot size, and efficiency, the temperature profiles of the weldment were determined using a two parameter heat flow model of laser beam welding. The thermal profiles from die center of the weldment, the chemistry of the base plate, and the prior austenite grain boundary were inputted into a thermodynamically based, empirical, computer model of the microstructural development of a weldment. A comparison of the experimental data and the computer calculation showed good agreement, but some differences. Both the agreement and the differences are discussed in terms of published continuous cooling curves for HSLA80 steels.