Can 316 stainless steel be welded?
Yes. 316 welds like 304, with ER316L filler and no preheat. Use 316L for thick sections, keep a little ferrite in the weld, and pickle or passivate afterwards.
316 is an austenitic stainless with 2-3% molybdenum added for chloride resistance, and it welds by every common process: TIG for tube and thin sheet, MIG for plate, resistance welding for sheet-metal assemblies, and laser welding for thin, precise seams. No preheat, no post-weld heat treatment, and no hardening in the heat-affected zone. The matching filler is ER316L (AWS A5.9) for wire and E316L for stick; do not substitute 308L, which lacks the molybdenum and leaves a weld that pits before the base metal in seawater or chloride service.
Sensitization is the same concern as on 304, and 316L (0.03% max carbon) is the answer for sections over about 6 mm (0.25") or for anything in corrosive service. Most 316 sold today is dual-certified 316/316L, so check the cert. A second, 316-specific point is hot cracking: fully austenitic weld metal cracks along the centreline as it solidifies. Standard 316L filler is balanced to solidify with 3-10% delta ferrite (FN 3-10 on the WRC diagram), which stops this. Very high-nickel base heats or over-diluted welds can go fully austenitic, so avoid excessive dilution and heat input on thick joints.
Cleanup is not optional on 316, because the molybdenum is bought for chloride resistance and heat tint throws it away. Back-purge tube and vessel welds with argon, then pickle (nitric-hydrofluoric paste or bath) or electropolish the weld zone and passivate per ASTM A967. Distortion, thermal expansion and low thermal conductivity are the same as 304: tack often, balance passes and fixture thin sheet.
Welding for 316 parts: where to send them
What to specify
- Base metal 316L (dual-cert 316/316L) per ASTM A240, A276 or A312, and call out 316L explicitly for sections over 6 mm or chloride service
- Filler ER316L (TIG, MIG) or E316L (stick); no 308L substitution
- Ferrite content of the deposited weld metal, typically FN 3-10, if the joint is thick or the service is critical
- Procedure qualification to AWS D1.6 or ASME IX with a weld map for pressure or sanitary work
- Argon back-purge on all tube, pipe and full-penetration welds
- Post-weld pickling or electropolishing plus passivation, with the heat tint acceptance level stated (none for wet or sanitary service)
- Surface finish on sanitary or pharmaceutical welds: ground and polished to the specified Ra, with no crevices
Pitfalls
- Welding 316 with 308L filler: the weld pits first in chloride service because it has no molybdenum
- Centreline hot cracking from a fully austenitic weld pool on thick, high-dilution joints
- Heat tint left in place on a marine or process part, which corrodes exactly where the molybdenum was supposed to help
- Sensitization from welding straight 316 in thick sections; use 316L
- Iron contamination from carbon-steel tools, wire brushes or grinding wheels
- Distortion on long thin welds; stainless expands about 50% more than carbon steel and conducts heat a third as well
Frequently asked questions
- What filler is used to weld 316 stainless?
- ER316L for TIG and MIG, E316L for stick. It matches the base metal and keeps the molybdenum content of the weld. 308L is not a substitute where corrosion resistance matters.
- Is 316 harder to weld than 304?
- No, it welds the same way. The only extra care is the ferrite balance of the weld metal to avoid hot cracking, which the standard 316L filler handles, and more thorough post-weld cleaning because the corrosion resistance is the reason the alloy was bought.
- Do 316 welds need to be pickled?
- For any wet, marine or process service, yes. Pickling or electropolishing removes the chromium-depleted heat tint; passivation alone will not. Hidden structural welds indoors can often be left as-welded, and the drawing should say which.
