Three-dimensional thermal simulation and experimental investigation of GTAW circumferentially butt-welded Incoloy 800 pipes

A three-dimensional finite element model was developed to simulate the multipass gas tungsten arc welding (GTAW) process of Incoloy 800 petrochemical pipes. The birth and death technique was used to consider mass addition from the ERNiCr3 filler metal into the weld pool. Movement of the GTAW torch was modelled in a discontinuous manner assuming a constant welding speed. The arc heat input was applied in the weld zone using different forms of surface, volumetric and combined heat flux distribution functions. In order to validate the thermal simulation model, temperature distribution within the heat-affected zone of the welds was precisely measured during the welding process by thermocouples. The simulation results showed that a fully volumetric arc heat input represents the best match to the thermocouple measurements for welding of the thin-walled pipes used in this work. It was also shown that increasing the heat input results in a wider weld pool root along with a higher maximum temperature of the heat-affected zone which is in agreement with the measurements. The present simulation model can be used as a proper tool to investigate the effect of different GTAW process parameters.