High-silicon austenitic stainless steel forging grade for pressure-retaining components in high-temperature service. Exceptional oxidation and corrosion resistance derived from elevated silicon and chromium content.
Austenitic SS
High-Temperature Service
Solution Annealed
Corrosion Resistant
Pressure-Retaining
UNS S32615
550 MPa min
Tensile Strength
220 MPa min
Yield Strength
192 HBW max
Hardness
7.6 g/cm³
Density
4.8–6.0 %
Si Content
Overview & Key Features
- High Silicon Content (4.8–6.0%) — Provides superior oxidation and corrosion resistance in high-temperature environments.
- Austenitic Structure — Fully austenitic in the solution-annealed condition, offering excellent toughness and non-magnetic behaviour.
- Corrosion Resistance — Excellent resistance to nitric acid, sulphuric acid, and general oxidising media due to high Cr (up to 19.5%) and Ni (up to 22%).
- High-Temperature Service — Rated for mechanical service up to 990°C and corrosion resistance up to 410°C.
- Pressure-Retaining Parts — Specifically designed for flanges, fittings, valve bodies, and fasteners per ASTM A182.
- Good Formability — 25% minimum elongation and high reduction in area allow complex forging geometries.
UNS S32615 Material Chemical Composition
| Element | Symbol | Min % | Max % | Specification Limit |
|---|---|---|---|---|
| Carbon | C | — | 0.070 | Max. |
| Silicon | Si | 4.800 | 6.000 | Range |
| Manganese | Mn | — | 2.000 | Max. |
| Phosphorus | P | — | 0.045 | Max. |
| Sulphur | S | — | 0.030 | Max. |
| Chromium | Cr | 16.500 | 19.500 | Range |
| Nickel | Ni | 19.000 | 22.000 | Range |
| Copper | Cu | 1.500 | 2.500 | Range |
| Molybdenum | Mo | 0.300 | 1.500 | Range |
| Iron | Fe | — | — | Balance |
UNS S32615 Material Mechanical Properties
ASTM A182 Specified Minimum Values
550MPa
Tensile Strength
[80 ksi] — Minimum
220MPa
Yield Strength
[32 ksi] — Minimum
25%
Elongation
in 2 in. / 50 mm or 4D
192HBW
Brinell Hardness
Maximum
| Property | Value (SI) | Value (Imperial) | Condition |
|---|---|---|---|
| Tensile Strength (UTS) | 550 MPa min | 80 ksi min | Annealed |
| Yield Strength (0.2% Proof) | 220 MPa min | 32 ksi min | Annealed |
| Elongation (2 in. / 50 mm) | 25% min | 25% min | Annealed |
| Reduction of Area | — | — | Not specified |
| Brinell Hardness | 192 HBW max | — | Annealed |
| Tensile Strength (Typical) | 620 MPa | 90 ksi | Annealed |
| Yield Strength (Typical) | 250 MPa | 36 ksi | Annealed |
| Elastic Modulus (Young’s) | 190 GPa | 28 × 10⁶ psi | Annealed |
| Shear Modulus | 75 GPa | 11 × 10⁶ psi | Annealed |
| Poisson’s Ratio | 0.28 | 0.28 | — |
| Fatigue Strength | 180 MPa | 26 ksi | Annealed |
| Shear Strength | 400 MPa | 58 ksi | Annealed |
| Brinell Hardness (Typical) | 170 HBW | — | Annealed |
| Elongation at Break (Typical) | 28% | — | Annealed |
| Reduction in Area (Typical) | 46% | — | Annealed |
Physical & Thermal Properties of UNS S32615 Material
Physical Properties
| Property | Value | Unit |
|---|---|---|
| Density | 7.6 | g/cm³ (480 lb/ft³) |
| PREN (Pitting Resistance) | 21 | — |
| Embodied Energy | 63 | MJ/kg |
| Embodied Carbon | 4.4 | kg CO₂/kg |
Thermal Properties
| Property | Value | Unit |
|---|---|---|
| Melting Point (Solidus) | 1310 | °C (2380 °F) |
| Melting Point (Liquidus) | 1350 | °C (2460 °F) |
| Specific Heat Capacity | 500 | J/kg·K |
| Thermal Expansion | 15 | μm/m·K |
| Latent Heat of Fusion | 370 | J/g |
| Max. Temp: Mechanical | 990 | °C (1810 °F) |
| Max. Temp: Corrosion | 410 | °C (780 °F) |
UNS S32615 Material Heat Treatment
| Process | Details |
|---|---|
| Solution Annealing | Heat uniformly to solution annealing temperature, hold for sufficient time, then quench in water or rapidly cool by other means. Produces a fully austenitic microstructure. |
| Typical Annealing Temperature | ≥ 1065°C (1950°F) — rapidly quenched thereafter |
| Cold Working | Not applicable as a hardening mechanism; grade relies on solid-solution strengthening. |
| Post-Weld Heat Treatment | Not typically required; however, full solution annealing may be specified where intergranular corrosion risk is a concern. |
Related Specifications & Standards
ASTM A182 / A182M
Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves for High-Temperature Service (primary specification)
ASTM A479
Stainless Steel Bars and Shapes for Use in Boilers and Other Pressure Vessels
ASTM A240
Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and General Applications
ASTM A312
Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes (sister product form spec for S32615)
ASTM A959
Standard Guide for Specifying Harmonised Standard Grade Compositions for Wrought Stainless Steels
ASME SA-182
ASME equivalent of ASTM A182, governing use in pressure vessel and boiler components under ASME Boiler and Pressure Vessel Code
Typical Applications of UNS S32615 Material
Flanges
Weld neck, slip-on, blind, threaded
Pipe Fittings
Elbows, tees, reducers, couplings
Valve Bodies
Gate, globe, check, ball valves
Fasteners
Bolts, studs, nuts, threaded rods
Plates & Bars
Forged and machined flat products
Rings & Discs
Pressure-retaining ring forgings
Chemical Processing
Nitric acid, sulphuric acid environments
Power Generation
Superheated steam lines, turbine components
