Stainless sheet moves when it gets hot. Set up joint, heat input and purge so the weld cools evenly—and then clean and passivate so it stays stainless.
Before you strike an arc
- Tight gaps; copper/aluminum backing bars; clamp on a flat table.
- Tacks every 50–100 mm; alternate; feather tacks before the final pass.
- ≤1.5 mm: autogenous TIG or small filler; 2–3 mm: pulsed MIG helps.
Keep panels flat
- Fast travel, low heat; pulse/stitch to limit puddle size.
- Skip‑weld and back‑step; balance around the part.
- Cool between passes; avoid quenching.
Purge and shielding
- Argon purge on backs/insides to prevent sugar; dams/tape for cavities.
- Gas lenses help on corners; avoid drafts.
After welding
- Remove spatter/heat tint with non‑ferrous abrasives.
- Pickle and passivate; rinse thoroughly; water‑break free surface.
Quick recipes
- 304, 1.2 mm corner: TIG, 1.6 mm 308L, low‑amp pulse; purge; tacks 75 mm; back‑step.
- 316L, 2.0 mm lap: Pulsed MIG with 316L wire; copper chill bars; passivate after.
FAQs & links
Q: Why rust spots after welding?
A: Usually contamination or no passivation—clean and repassivate.
Baoli Engineering Team · Reviewed Oct 31, 2025