Complete guide to welding stainless steel. Learn about filler selection, corrosion protection, distortion control, and maintaining weld quality.
Introduction
Stainless steel welding requires careful attention to maintain corrosion resistance and mechanical properties. At Fulei Metal, we weld stainless steel components for food, medical, marine, and chemical industries worldwide.
Challenges of Stainless Steel Welding
Corrosion Resistance
Heat-affected zone can lose corrosion resistance. Carbide precipitation at 450-850 degrees C (sensitization). Proper filler and procedures prevent issues. Post-weld treatment may be required.
Thermal Expansion
Stainless steel expands 50% more than carbon steel. More distortion. Requires careful clamping and sequencing.
Thermal Conductivity
Lower conductivity means heat stays localized. Steeper thermal gradients. Faster weld pool solidification. Risk of incomplete fusion.
Oxidation
Chromium oxide forms at high temperatures. Must be shielded properly. Back-purging required for full-penetration welds. Post-weld cleaning removes heat tint.
Filler Metal Selection
304 Stainless
ER308L: standard filler for 304. Low carbon prevents sensitization. ER308LSi: improved silicon for better wetting.
316 Stainless
ER316L: standard filler for 316. Molybdenum for pitting resistance. ER316LSi: improved wetting.
Dissimilar Welding
ER309L: for welding stainless to carbon steel. ER312: for difficult-to-weld dissimilar combinations.
TIG Welding Stainless Steel
DC Operation
DC electrode negative (straight polarity). Tungsten electrode (thoriated or lanthanated). Argon shielding gas. Clean, precise welds.
Parameters
1 mm: 40-70 amps, 8-10 lpm argon. 2 mm: 70-110 amps, 10-12 lpm. 3 mm: 100-140 amps, 10-12 lpm. Pulse for thin materials.
Back Purging
For full-penetration welds, purge the back side with argon. Prevents oxidation and sugar (black oxide). Critical for food and medical applications.
MIG Welding Stainless Steel
Gas Selection
Argon with 2% oxygen (Ar-O2). Or tri-mix (Ar-He-CO2). Never use standard CO2 mixtures (causes corrosion).
Parameters
1 mm: 60-90 amps, 15-17V. 2 mm: 90-130 amps, 17-19V. 3 mm: 130-170 amps, 19-21V.
Distortion Control
Tack weld frequently. Alternate weld positions. Use backing bars (copper or aluminum). Clamp firmly. Weld sequence to balance heat. Pulse to reduce heat input.
Post-Weld Treatment
Removing Heat Tint
Mechanical: wire brushing with stainless brush. Chemical: pickling paste or acid cleaning. Electrochemical: electrolytic cleaning. Plasma: plasma cleaning.
Passivation
Restores chromium oxide layer. Acid treatment (nitric or citric acid). Removes free iron. Restores corrosion resistance.
Common Problems
Sensitization: use L-grade filler, minimize time at 450-850 degrees C. Distortion: clamp, sequence, reduce heat input. Porosity: clean material, check gas coverage. Cracking: use correct filler, control heat input. Oxidation: back purge, check gas flow.
Applications
At Fulei Metal, we weld stainless steel for: food processing equipment, medical devices, pharmaceutical equipment, marine hardware, architectural elements, and chemical processing.
Conclusion
Stainless steel welding requires attention to corrosion resistance, distortion, and oxidation. At Fulei Metal, our experience and procedures ensure quality stainless steel welds for demanding applications.