Scaling modelling of penetration in high productivity gas tungsten arc welding

A novel semi-empirical equation in explicit form is presented for the estimation of weld penetration in high productivity Gas Tungsten Arc Welding (GTAW). The approach followed in developing the final expression is based on the methodology of scaling analysis applied to the description of the process according to the heat transfer theory. The equation developed is applicable under the condition of gouging penetration usually encountered in arc welding processes and accounts for heat absorbed by phase change, heat carried away by the molten metal, heat lost by conduction in the substrate, and the effect of penetration on arc length. The equation proposed requires as inputs: specific and latent heat, density, and solidus temperature of the substrate and welding speed, current, voltage, and stand-off distance. Welding experiments on five classes of materials (ASTM A36 structural steel, AISI 304 stainless steel, CP aluminium, AA 5083, and CP titanium) were performed to validate the model proposed under welding speed ranging from 3.9 to 19 mm/s and current going from 240 to 700 A. Predictions of penetrations calculated by the final model result in an mean percentage error of -0.87% with a standard deviation of 9.52%. The ultimate purpose of this model is to provide a simple and accurate expression useful for the selection of process parameters when using high productivity GTAW, especially to join novel alloys.