Materials
300-series stainless, from coil
Austenitic stainless wire for frames, grids, trays, and furnace fixtures. We form the 300-series — including 330 — in 4–14 mm, with 3/8, 7/16, and 1/2 in as stock diameters. “SS” is not a spec.
What 300-series actually is
300-series stainless is austenitic: chromium-nickel, non-magnetic in the annealed condition, work-hardening as you bend it. It comes as coil. That coil is what a 3D CNC or 2D CNC cell feeds. It is not 1018 with a better name, and it is not one alloy.
Compared with cold-roll 1010 / 1018: more springback, more tool galling, a larger minimum inside radius (start at 1.5–2× diameter), and passivate after form and weld — not zinc. Resistance weld still works on many crosses; TIG shows up on rims, 330, and thin-to-heavy joints.
Production band: 4–14 mm (0.157–0.551 in). Stock sizes: 3/8, 7/16, and 1/2 in.
Grades we see on coil
| Grade | UNS | Forming note |
|---|---|---|
| 301 | S30100 | Work-hardens fast. Springier than 304. Watch min radius and tool galling. |
| 302 | S30200 | Classic stainless forming wire. A bit more carbon than 304, more snap. Common clip and form grade. |
| 304 / 304L | S30400 / S30403 | General 300-series coil. Food, architectural, outdoor grids. 304L when weld carbide precipitation is a spec. |
| 305 | S30500 | Lower work-hardening. Used when a severe cold form would crack 304. |
| 316 / 316L | S31600 / S31603 | Molybdenum, better chloride resistance. More expensive, more springback than 304. Marine and chemical. |
| 317 / 317L | S31700 / S31703 | Higher Mo than 316. Spec-driven, not a default coil. |
| 309 / 310 | S30900 / S31000 | Higher Cr/Ni, heat and oxidation. Furnace-adjacent; still not 330. |
| 321 / 347 | S32100 / S34700 | Ti- or Nb-stabilized. Welded high-temp service when 304L is not the spec. |
| 330 (N08330) | N08330 | Stock high-temp coil for heat-treat wire baskets and furnace fixtures. Ni-Cr, not “stainless 304 with a bigger number.” |
| 201 / 202 | S20100 / S20200 | Mn austenitics. Sometimes substituted for 304. Call the real grade; do not accept “equiv.” |
308 is a filler metal, not a forming coil. If the print says 308 wire, they likely mean a weld rod — or they meant 304.
302 vs 304 vs 316 vs 330
| If you meant… | Use | Do not substitute |
|---|---|---|
| General stainless form, indoor/outdoor, food-adjacent | 304 or 304L | 201 “equiv,” 430, plated 1018 |
| A form that has to snap or hold a clip force | 302 (or 301 if the path is mild) | Soft 304 annealed, hoping it will act like spring |
| Chlorides, marine, chemical washdown | 316 / 316L | 304 with extra passivate |
| Welded 304 that must stay low-carbon in the HAZ | 304L | 304 and a prayer after MIG |
| Heat-treat wire basket, furnace fixture, high-temp air | 330 (N08330) | “High 300,” 309, 310, or 321 as a silent swap |
| A severe cold form that cracks 304 | 305, or anneal + re-form | A tighter CAD radius |
330 is listed with the 300s because buyers search it that way. Metallurgically it is a Ni-Cr high-temp alloy (N08330), not a 304 with a bigger number. Price, nickel, forming load, and weld are in another class. Heat-treat wire baskets start with the cert, not the mesh pitch.
Forming 300-series in this band
- Inside radius — 1.5–2× diameter on 304/316 at 4–14 mm. 3/8 in wire → about 9/16–3/4 in IR. 1/2 in wire → 3/4–1 in. Mild-carbon 1× rules do not apply.
- Springback — the program overbends. Change 304 to 302 (or hard to annealed) and the first article is scrap. Name tensile / temper on the print.
- Work hardening — 301 is the extreme. Each bend raises strength and the next bend’s load. A 3D path that is easy in 1018 can lock a 301 coil.
- Galling — stainless sticks to tooling. Lubrication, polish, and sometimes a different pin material. A carbon setup with the pressure turned up will mark the wire and grab.
- Straightener — leftover cast is worse on long 304 spans. Straighten for the tensile, not for 1018.
Full geometry rules: design for wire forming.
Weld on 300-series grids and frames
Mesh grids and cable trays in 304 are usually resistance-welded at the crosses, then MIG or TIG on rims and mounts. 316 behaves similarly with more heat input discipline. 330 often wants TIG on the fixture joints — confirm a nugget before you assume a carbon grid welder scales.
- 304 vs 304L: L if the weld spec cares about sensitization
- Filler: 308/308L for 304, 316L for 316, nickel-bearing for 330 — not “stainless rod”
- Flash and discoloration: as-welded, or cleaned / passivated after
- Distortion: fixture 3/8–1/2 in frames; stainless moves
Process pages: resistance welding, MIG / TIG.
Finish is passivate, not paint
After form and weld, 300-series is cleaned and passivated unless the print says mill finish. Zinc and powder are carbon finishes. A “stainless look” on 1018 is plating, not 304. Sequence: plating and coating.
At 3/8, 7/16, and 1/2 in
| Size | Common 300-series jobs |
|---|---|
| 3/8 in (9.53 mm) | 304/316 trays, guard frames, medium mesh rims, 302 forms |
| 7/16 in (11.11 mm) | Heavier 304 rims, 316 washdown frames, 330 wire-basket borders |
| 1/2 in (12.7 mm) | Structural 304, 330 rod frames, furnace fixtures |
302 clip wire at 0.020–0.080 in is not this cell. Same family, different machine. We will say so.
What is not 300-series forming coil
- 303 — free-machining, sulfur. Not a drawing coil we run. If you meant a form, you meant 304 or 302.
- 400-series (410, 430) — ferritic / martensitic. Different magnetism, weld, and rust story. Ask before assuming the 300 cell.
- 2205 and other duplex — not a 304 setup.
- Inconel and nickel beyond 330 — cert and conversation, not a pressure increase on 304 tooling.