Tungsten active gas (TAG) welding of austenitic stainless steel sheet with Ar + H₂ gas mixture

Abstract

TIG welding is used when a good weld appearance and a highest quality of the weld are required. Nevertheless, the process has also some major disadvantages like relatively shallow penetration capability and low productivity. To increase the penetration and/or productivity, instead of traditional pure Ar, gas mixtures containing gases with high thermal conduction can be used. For austenitic stainless steels, as they are not prone to hydrogen cracking, also H2 is suitable. As H2 is active gas, the process is called Tungsten Active Gas (TAG). In this research, austenitic stainless steel sheet was welded with a competitive welding speed of 40 cm min1, with pure argon and with Ar+7.5 %H2 mixture. With pure Ar, a welding current of 220 A was far too small to reach full penetration in 3 mm sheet. With the 7.5 %H2 active gas mixture, only 130 A was sufficient with unchanged welding speed.