SS · stainless
Stainless Steel 316L
Harder to machine than 304 and it galls more, but it is the grade for chlorides, medical and marine. Published index around 36% against B1112 = 100%.
Quoting this material
- Typical lead time
- 8–14 working days
- Condition
- Annealed, low carbon for welded assemblies
- Achievable finish
- Ra 1.6 µm typical · Ra 0.4 µm best
Choosing between two grades? 304 vs 316L compared →
Machined in-house to your drawing: see the precision CNC machining service and the machine and inspection capability it runs on.
Machinability
Our own 1–10 shop ranking, not a published index: 10 is free-cutting brass C360, 1 is Inconel 718. It ranks how a material behaves on the floor - cycle time, chip control and tool life together. Where a published index exists it is quoted in the note.
Harder to machine than 304 and it galls more, but it is the grade for chlorides, medical and marine. Published index around 36% against B1112 = 100%.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength | 485 | MPa |
| Yield strength (0.2%) | 170 | MPa |
| Elongation | 40 | % |
| Hardness | 217 | HB |
| Thermal conductivity | 16.3 | W/m·K |
| Modulus of elasticity | 193 | GPa |
Hardness, tensile and thermal figures are typical published values for the condition stated. Actual mill certificates govern; send the specification with the drawing and we confirm against the certificate before the material is cut.
Condition
Annealed, low carbon for welded assemblies
Heat treatment
Not hardenable by heat treatment. Solution annealing after welding restores corrosion resistance by dissolving carbides; it does not change strength.
Achievable surface finish
Ra 1.6 µm
Ra 0.4 µm
Electropolishing is common for medical and pharmaceutical parts - it removes the outer layer where inclusions sit and leaves a surface that resists both corrosion and bacteria.
Tooling and cutting parameters
Cutting speed
- 80–150 m/min (carbide)
Feed
- 0.10–0.25 mm/rev turning · 0.06–0.15 mm/tooth milling
Tooling
- AlTiN coated, sharp, strong edge; expect 2–3× the insert consumption of 304
Coolant
- High-pressure flood; through-tool coolant wherever the geometry allows
Starting points for carbide on a rigid setup, not a guarantee. The right numbers depend on the machine, the toolholder and the fixturing - ask and we will say what we would actually run.
Typical applications
- Medical instruments and implants hardware
- Pharmaceutical and bioprocess equipment
- Marine and offshore components
- Chemical and petrochemical fittings
- Food processing in chloride environments
DFM notes for this grade
- The molybdenum addition is what resists chlorides - do not accept a 304 substitution on a chloride job however similar the datasheet looks
- It galls: two 316L surfaces under load will seize unless one is a different material or the surfaces are hardened and lubricated differently
- Low carbon means lower yield: a 316L part is slightly less stiff in a press fit than a 304 part, which matters on thin-wall designs
Questions buyers ask
- When must it be 316L rather than 304?
- Chlorides, salt water and most pharmaceutical or medical service. 304 resists most fresh-water and atmospheric corrosion; it pits in a chloride environment where 316L survives. If the part is cleaned with a chloride sanitiser, that counts.
- Does 316L gall worse than 304?
- It has a reputation for it, and the molybdenum that helps with corrosion does not help with galling. The fix is not the stainless grade at all: pair it against a bronze, use a hardened and polished surface, or accept a lubricated joint.
Grades we would quote instead
304 / 304L
4/10Work-hardens faster than the tool can cut if the feed drops.
2205 Duplex
2/10Roughly twice the yield of 316L and about twice as unpleasant to machine.
17-4 PH
4/10In the annealed condition it machines like a tough 304; in H900 it is hard enough that finishing has to be done by grinding or hard turning.