High-Silicon Austenitic
Stainless Steel
Pressure-retaining forging alloy engineered for demanding high-temperature service. Elevated silicon and chromium content deliver outstanding oxidation and corrosion resistance where standard grades fall short.
Tensile Strength
Yield Strength
Hardness
Density
Si Content
Overview & Key Features
High Silicon Content 4.8-6.0%
Superior oxidation and corrosion resistance in high-temperature environments, distinguishing S32615 from conventional austenitic grades.
Fully Austenitic Structure
Austenitic in the solution-annealed condition, providing excellent toughness, ductility, and inherently non-magnetic behaviour.
Corrosion Resistance
Exceptional resistance to nitric acid, sulphuric acid, and oxidising media driven by elevated Cr (up to 19.5%) and Ni (up to 22%).
High-Temperature Service
Rated for mechanical service to 990C and corrosion resistance up to 410C - ideal for aggressive process environments.
Pressure-Retaining Parts
Specifically qualified for flanges, fittings, valve bodies, and fasteners per ASTM A182 requirements.
Good Formability
25% minimum elongation and substantial reduction in area facilitate complex forging geometries without cracking.
Chemical Composition
| Element | Symbol | Min % | Max % | Limit Type |
|---|---|---|---|---|
| Carbon | C | - | 0.070 | Maximum |
| Silicon | Si | 4.800 | 6.000 | Range |
| Manganese | Mn | - | 2.000 | Maximum |
| Phosphorus | P | - | 0.045 | Maximum |
| Sulphur | S | - | 0.030 | Maximum |
| 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 |
Mechanical Properties
Tensile Strength
Yield Strength (0.2%)
Elongation
Brinell Hardness
| Property | SI Value | Imperial Value | 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 |
| 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 x 10^6 psi | Annealed |
| Shear Modulus | 75 GPa | 11 x 10^6 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
Physical Properties
| 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
| Melting Point (Solidus) | 1310C (2380F) |
| Melting Point (Liquidus) | 1350C (2460F) |
| Specific Heat Capacity | 500 J/kg.K |
| Thermal Expansion | 15 um/m.K |
| Latent Heat of Fusion | 370 J/g |
| Max Temperature (Mechanical) | 990C (1810F) |
| Max Temperature (Corrosion) | 410C (780F) |
Heat Treatment
Solution Annealing
Heat uniformly to solution annealing temperature, hold for sufficient time to achieve a homogeneous single-phase austenitic microstructure, then quench in water or rapidly cool by other approved means.
>= 1065C (1950F)Cold Working
Not applicable as a primary hardening mechanism for this grade. UNS S32615 relies on solid-solution strengthening from its elevated alloying additions rather than work hardening.
Post-Weld Heat Treatment
Not typically required for welded assemblies. Full solution annealing may be specified by the engineer of record where intergranular corrosion risk is identified as a concern in the service environment.
Related Specifications & Standards
Primary Governing Specification
Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves for High-Temperature Service.
Bars & Shapes
Stainless Steel Bars and Shapes for Use in Boilers and Other Pressure Vessels.
Plate, Sheet & Strip
Chromium and Chromium-Nickel Stainless Steel Plate, Sheet, and Strip for Pressure Vessels and General Applications.
Seamless & Welded Pipe
Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes - sister product form specification for S32615.
Harmonised Grade Guide
Standard Guide for Specifying Harmonised Standard Grade Compositions for Wrought Stainless Steels.
ASME Equivalent
ASME equivalent of ASTM A182 governing use in pressure vessel and boiler components under the ASME Boiler and Pressure Vessel Code.
Typical Applications
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
UNS S32615 Products
Available from USA Piping Solutions
