Structure and texture simulations in fusion welding processes – comparison with experimental data

Abstract

The Cellular Automaton-Finite Element (CAFE) method is used to simulate grain structure evolution during gas tungsten arc welding of 316 L steel plates. The experimental configuration is designed for in-situ observations of the melt pool and liquid flow. It is complemented by electron back scattered diffraction analyses to reveal the texture resulting from melting and solidification. Simple configurations are used to facilitate comparisons with simulations, that consider no addition of metal (remelting process) and constant power for two welding speeds. It is found that the melt pool shape can be very well retrieved for the two welding speeds providing that the relation between the dendrite tip growth velocity and the undercooling is adjusted. As a result, the computed grain structure reaches good agreement with measurements in terms of morphology, orientation and texture. A standard growth kinetics model underestimates the melt pool shape and results in large deviation of the simulated grain structure with measurements. The plate subsidence after processing reaches a maximum deflection at the center of the weld seam. It is also measured and compared to the simulations that include free metal/gas boundaries, showing satisfying results despite a weaker calculated fluid flow. Finally, the chaining and coupling schemes of the CAFE model are both studied in order to quantitatively evaluate their roles on the predicted melt pool shape and grain structure. The coupling scheme reveals better coherency between macroscopic results and grain structure simulation.