Numerical and Experimental Studies of the Influence of Process Gases in Tig Welding

This paper presents extensive investigations about the influence of He-additions to argon TIG-arc properties. Results of diagnostic methods, numerical simulations and welding trials are combined to improve the comprehension about the mode of action of gas mixtures. Additionally, selected results of the investigation with H2- and N2-additions are summarized. The investigations show that all gas additions cause an increase of the heat input into the workpiece. However, the stagnation pressure depends on the gas composition: He-additions result in a decrease of the stagnation pressure which depends on the arc length, whereas H2-and N2-additions increase the pressure. By a systematic choice of the gas mixture the weld depth and also the maximum feed speed can be influenced.