Which one should the drawing call out?
304 for a dry or benign housing, 316L where the housing sees coolant, road salt or a chloride-bearing condensate for the life of the vehicle. If the part is welded or heavily drawn, 316L's low carbon content removes the sensitisation risk that 316 carries.
| 304 / 304L | 316 / 316L | |
|---|---|---|
| Corrosion resistance | Good for coolant, condensate and road salt under normal automotive exposure | Better: molybdenum content resists chloride pitting and crevice attack |
| Magnetism | Effectively non-magnetic in the annealed state | Effectively non-magnetic; cold work raises magnetic response slightly |
| Drawability | The reference grade for deep drawing; the widest proven window | Lower draw ratio per stage; more stages or more anneals on deep parts |
| Springback | Lower | Higher - the die has to be built for it |
| Welding | Weldable; 304L preferred where welded | Weldable; 316L is the welded variant |
| Cost | Lower (no molybdenum) | Higher, and the gap widens with nickel and molybdenum prices |
| Typical use here | General sensor housings, shields, dry-side parts | Coolant-side housings, salt-exposed parts, corrosive condensate |
Published configurations
Balford publishes 47 configurations in SUS 304 and 57 in SUS 316. Both grades run across oxygen, NOx, ABS, EGT, motorcycle and fitment series, so switching grade inside a family is a normal change rather than a new part family.
| Grade | Configurations | Height range (mm) | OD range (mm) |
|---|---|---|---|
| SUS 304 | 47 | 0.1-48.5 | 9.10-80.00 |
| SUS 316 | 57 | 0.3-58.5 | 1.20-21.60 |
How the decision is usually made
- Write the service environment on the drawing: what the housing is exposed to, at what temperature, and for how long.
- If it is coolant, salt or chloride-bearing condensate, specify 316L and accept the forming cost.
- If it is dry and moderate, 304 or 304L keeps tooling simpler and material cheaper for the same function.
- Do not specify 316 "to be safe": the extra stiffness and springback change the tooling, and the premium buys nothing in a benign environment.
Both grades are drawn in house on presses from 25 t to 350 t, with deep drawing up to Ø250 mm. ISO 9001:2015 quality system, with process controls aligned to IATF 16949 requirements.