WHICH STAINLESS STEEL GRADES CAN BE FABRICATED AND WELDED?
Most stainless steel fabrication runs on two grades, 304 and 316, because they're easy to form, easy to weld, and hold up well against corrosion. Other stainless families trade some of that away for hardness, strength, or cost. 420 and 440 are hardenable grades built for wear and cutting edges, not welded assemblies.
If a drawing calls for a grade outside 304 or 316, it's worth knowing what that grade does to cost, lead time, and weld quality before it goes out for quote.
Published September 24, 2026 · JMC Fabrication
- Austenitic (304, 304L, 316, 316L) — The workhorse family. Non-magnetic in the annealed condition, very formable, and the easiest stainless to weld. The L grades have lower carbon, which keeps the heat-affected zone from losing corrosion resistance after welding. 316 adds molybdenum for better chloride resistance, which is why it's the coastal and marine choice.
- Ferritic (409, 430) — Magnetic, cheaper, and decent in mild corrosion service. 409 is common in exhaust systems and 430 in appliance and trim work. They weld, but the heat-affected zone can lose toughness through grain growth, so they're used more for sheet work than for structural parts.
- Duplex (2205, 2507) — A mix of austenite and ferrite that gives roughly twice the strength of 316L and much better resistance to chloride stress corrosion cracking. It welds well with qualified procedures and controlled heat input.
- Martensitic (410, 420, 440) — Hardenable by heat treatment, like tool steel. That's what makes them good for knives, valve trim, pump shafts, and wear parts, and it's also what makes them hard to weld.
- Precipitation-hardening (17-4 PH) — High strength after an aging heat treatment, used for shafts, fasteners, and aerospace and valve components. It's more often machined than fabricated.
420 stainless has enough carbon to harden well. It can be welded, but it usually needs preheat, careful interpass temperature control, and post-weld heat treatment to avoid cracking and to bring back toughness in the heat-affected zone. Filler selection matters too. None of that is exotic, but it adds steps, time, and cost that a 304 or 316 weldment doesn't need.
440 grades, especially 440C, carry around 1% carbon. That's great for hardness and edge retention and poor for welding. 440C is generally considered unsuitable for welded fabrication. Parts made from it are almost always machined from bar and heat treated, not built up from welded pieces.
- 304 / 304L: excellent, the default for general stainless fabrication
- 316 / 316L: excellent, the default for coastal, marine, and chemical exposure
- 2205 duplex: good with qualified procedures and heat input control
- 409 / 430 ferritic: fair, best for sheet and non-structural work
- 410 / 420 martensitic: difficult, needs preheat and post-weld heat treatment
- 440A / 440B / 440C martensitic: poor, generally machined rather than welded
Ask what the grade is doing. If the part needs a hard wear surface or a cutting edge, 420 or 440 may be right, and the part is probably a machined component rather than a fabrication. If it's a bracket, housing, or frame that ended up with a hardenable grade out of habit or a copied spec, 304 or 316 will almost always fabricate faster, weld cleaner, and resist corrosion better.
Mixed designs are common too: a 316 welded assembly with a separately machined and hardened 420 or 440 wear part bolted in where it's needed.
For welded stainless fabrication, 304 and 316 cover most of the work, duplex covers the high-strength and high-chloride cases, and martensitic grades belong on machined wear parts. Matching the grade to the job before it goes out for quote saves cost and rework.
JMC Fabrication's stainless work runs on 304 and 316 for commercial, marine, and industrial customers across the Gulf Coast, out of a 50,000 sq ft shop in Pascagoula, MS.
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