Argon / Nitrogen Mix
Overview
Small amounts of nitrogen have been added to Ar-1% 02 to achieve a completely austenitic microstructure in welds made with type 347 stainless steel filler metal. Nitrogen concentrations in the range of 1.5 to 3% have been used. Quantities above 10% produced considerable fuming but welds are sound. Additions greater than 2% N2 produced porosity in single pass GMAW welds made in mild steel; additions less than 1/2% caused porosity in multi-pass GMAW welds in carbon steel. A few attempts have been made to utilize N2 rich argon mixtures for GMAW welding of copper and its alloys, but spatter percentage is high.
Gas Blends
Argon with 2-5% Nitrogen
In short-circuiting yields good weld shape and color and increases welding speed. For spray and pulsed spray transfer it is nearly equivalent to other trimixes. When joining stainless to carbon steels in presence of nitrogen, care has to be taken to ensure the proper weld microstructure. Nitrogen increases arc stability and penetration and reduces distortion of the welded part. In duplex stainless steels assists in maintaining proper nitrogen content.