SS · stainless
Duplex Stainless Steel 2205 (UNS S32205)
Roughly twice the yield of 316L and about twice as unpleasant to machine. High cutting forces, poor chip breaking, and tool life that has to be planned rather than hoped for.
Quoting this material
- Typical lead time
- 15–20 working days
- Condition
- Annealed / solution annealed
- Achievable finish
- Ra 1.6 µm typical · Ra 0.8 µm best
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.
Roughly twice the yield of 316L and about twice as unpleasant to machine. High cutting forces, poor chip breaking, and tool life that has to be planned rather than hoped for.
Properties as supplied
| Parameter | Value | Unit |
|---|---|---|
| Tensile strength | 620 | MPa |
| Yield strength (0.2%) | 450 | MPa |
| Elongation | 25 | % |
| Hardness | 290 | HB |
| Thermal conductivity | 14 | W/m·K |
| Modulus of elasticity | 200 | 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 / solution annealed
Heat treatment
Solution annealing is required after welding to restore the ferrite/austenite balance. Heat treatment in the shop is avoided: the wrong thermal cycle unbalances the structure and destroys both corrosion resistance and toughness.
Achievable surface finish
Ra 1.6 µm
Ra 0.8 µm
Machining raises residual stress, and duplex is sensitive to it - a passivation and, on critical parts, a pickled or electropolished finish is standard.
Tooling and cutting parameters
Cutting speed
- 60–110 m/min (carbide)
Feed
- 0.08–0.20 mm/rev turning · 0.05–0.12 mm/tooth milling
Tooling
- Tough AlTiN-coated carbide, strong edge, generous corner radius; avoid sharp geometry that chips
Coolant
- High-pressure flood, aimed at the edge - heat management is the whole game
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
- Offshore and subsea pipework
- Desalination and seawater systems
- Chemical process vessels
- Pulp and paper equipment
- Heat exchanger tubesheets
DFM notes for this grade
- Only specify it where the chloride stress-corrosion resistance is genuinely needed - it costs roughly 3–4× a 316L part to machine for the same geometry
- Duplex is notch sensitive: a sharp corner or a rough surface finish is a fatigue initiator, so radii and finish are functional requirements
- Do not let a subcontractor heat it. Thermal cycles unbalance the phases; solution annealing is a controlled process with a documented cooling rate
Questions buyers ask
- When is duplex worth 3× the price of 316L?
- When the environment destroys 316L: chlorides plus stress plus temperature, which is exactly where 316L stress-corrosion cracks. Seawater systems, desalination and sour gas service are the classic cases, and the alternative is a much more expensive nickel alloy.
- Why is duplex so hard to machine?
- Because it is a two-phase structure and the two phases machine differently - the austenite work-hardens while the ferrite does not, so the tool edge sees inconsistent cutting conditions. It also has low thermal conductivity, so heat concentrates at the edge.