Materials
How to weld stainless steel
Quick answer
To weld stainless steel: use TIG for quality, MIG with tri-mix or 98/2 argon-CO2 for speed, filler matched to the parent metal (ER308L (304 grade), ER316L (316 grade) — match the parent metal), and prepare properly — dedicated stainless brushes and discs — carbon steel contamination causes rust later. The key adjustment vs mild steel: about 10% less current than mild steel.
Process and filler
Process: TIG for quality, MIG with tri-mix or 98/2 argon-CO2 for speed. Filler: ER308L (304 grade), ER316L (316 grade) — match the parent metal. Low thermal conductivity but retains heat: lower amps (~10% under mild steel), faster travel, or it sugars and distorts
Preparation
Dedicated stainless brushes and discs — carbon steel contamination causes rust later. Fit-up matters more than most beginners expect: a gap you can see daylight through is a gap the filler has to fill, at the cost of heat control.
Amps and approach
Set current by thickness as you would for steel, then apply the adjustment: about 10% less current than mild steel. Run test coupons first — every stainless steel joint tells you loudly when the parameters are wrong.