Per IIW Commission IX guidelines and ESAB Fabrication Handbook, nitrogen content in the shielding gas for GTAW should be 1.5-3%, and for GMAW 2-3%. Too little nitrogen increases the risk of sigma phase formation in multipass welds, which embrittles the weld and reduces corrosion resistance. Too much nitrogen can cause porosity in the root pass.
Heat input must be kept between 0.5 and 2.5 kJ/mm for 22Cr duplex, with interpass temperature below 150?C. Higher heat inputs or interpass temperatures promote sigma and chi phase precipitation, leading to loss of toughness and corrosion performance.
Post-weld cooling rate also matters. Rapid cooling through the 800-500?C range is beneficial to avoid sigma phase. For heavy sections, forced air cooling may be necessary.
What is your go-to method for verifying nitrogen content in the shielding gas on site?