254SMO · UNS S31254 · W. Nr. 1.4547 · ASTM A182 F44 · 015Cr20Ni18Mo6CuN
254SMO / Alloy 254 (6 Mo Super Austenitic) (S31254): composition, properties, fittings and flanges
254SMO, also supplied as UNS S31254 (W. Nr. 1.4547, ASTM A182 F44), is a 6 % molybdenum super austenitic stainless steel containing about 20 % chromium, 18 % nickel, 6 % molybdenum, 0.7 % copper and 0.20 % nitrogen. That combination gives a pitting resistance equivalent number above 43 - similar to some nickel alloys - with…
- UNS
- S31254
- W. Nr.
- 1.4547
- Density
- 8.00 g/cm³ (0.289 lb/in³)
- Key strength
- 650 MPa / 94 ksi
Identification and standards
| Short form | 254SMO · UNS S31254 · W. Nr. 1.4547 · ASTM A182 F44 · 015Cr20Ni18Mo6CuN |
|---|---|
| Classification | Six percent molybdenum super austenitic stainless steel |
| UNS | S31254 |
| Werkstoff number | 1.4547 |
| Material family | Stainless Steel |
Chemical composition
| Element | Composition (wt %) | Why it is there |
|---|---|---|
| Chromium (Cr) | 19.5 - 20.5 | Passive film, pitting resistance |
| Nickel (Ni) | 17.5 - 18.5 | Austenite stability, chloride SCC resistance |
| Molybdenum (Mo) | 6.0 - 6.5 | Primary pitting and crevice resistance |
| Nitrogen (N) | 0.18 - 0.22 | Strength plus pitting resistance |
| Copper (Cu) | 0.50 - 1.00 | Reducing acid resistance |
| Manganese (Mn) | 1.00 max | - |
| Silicon (Si) | 0.80 max | - |
| Phosphorus (P) | 0.030 max | - |
| Sulphur (S) | 0.010 max | - |
| Carbon (C) | 0.020 max | Low carbon for as-welded service |
| Iron (Fe) | Balance | Matrix |
Note Single figures are maximum limits unless shown as a range. Always confirm against the heat-specific EN 10204 3.1 certificate supplied with your order.
Mechanical properties
| Tensile strength, min (ASTM A240) | 650 MPa / 94 ksi |
|---|---|
| 0.2 % yield strength, min | 300 MPa / 44 ksi |
| Elongation in 2 in, min | 35 % |
| Maximum hardness | 223 HB / 96 HRB |
| Typical pitting resistance equivalent number | Above 43 |
| Recommended service temperature range | -196 °C to 400 °C |
Warning Values depend on product form, section thickness and heat treatment. Larger sections generally achieve lower strength than thin product; always design against the applicable code allowable stress rather than these figures.
Physical properties
| Density | 8.00 g/cm³ (0.289 lb/in³) |
|---|---|
| Melting range | 1320 - 1400 °C (2410 - 2550 °F) |
| Modulus of elasticity | 195 GPa (28.3 x 10⁶ psi) |
| Thermal conductivity at 20 °C | 13.5 W/m·K |
| Mean coefficient of thermal expansion, 20-100 °C | 16.5 µm/m·°C |
| Electrical resistivity at 20 °C | 0.85 µΩ·m |
| Magnetic behaviour | Non-magnetic when annealed |
Specifications by product form
| Pipe, seamless / welded | ASTM A312 / A358 / ASME SA-312, ASTM A813 / A814 |
|---|---|
| Tube | ASTM A213 / A269 / A249 |
| Plate / sheet / strip | ASTM A240 / ASME SA-240 (UNS S31254) |
| Bar / rod / shapes | ASTM A276 / A479 / ASME SA-479 |
| Forgings & flanges | ASTM A182 Grade F44 / ASME SA-182 |
| Butt weld fittings | ASTM A403 / ASME SA-403 (WP254SMO / S31254) |
| Welding consumables | Over-alloyed fillers such as ERNiCrMo-3 or high-Mo nickel alloys for critical joints |
| UNS / EN / China | UNS S31254 · W. Nr. 1.4547 · GB 015Cr20Ni18Mo6CuN |
Product forms available
Hangbo supplies this grade in the following forms. Sizes outside the listed range can often be produced to order.
- Seamless and welded pipe and tube
- Butt weld elbows, tees, reducers and caps to ASME B16.9
- Forged flanges to ASME B16.5 Class 150-600
- Machined heat exchanger components and fasteners
Typical applications
- Seawater cooling, condensers, heat exchangers and piping on ships and platforms
- Flue gas desulphurisation absorber towers, outlet ducts and slurry piping
- Pulp and paper chlorine dioxide bleaching towers and washer drums
- Reverse osmosis systems, brine concentrators and desalination equipment
- Pharmaceutical and fine chemical plant with high chloride duties
- Oil and gas produced water, seawater injection and hydraulic lines
Welding, forming and machining
- Welding
- Weld with GTAW or GMAW using over-alloyed nickel-based filler such as ERNiCrMo-3 for the most aggressive duties. Keep heat input below about 1.5 kJ/mm and interpass temperature below 100 °C, with argon backing gas.
- Hot forming
- Solution anneal at 1150-1200 °C followed by rapid water quench. Hot work between 1200 °C and 950 °C; avoid the 600-1000 °C range where sigma and chi phases form.
- Machining
- Higher nickel and molybdenum raise cutting forces. Use sharp positive rake carbide, low speeds, high feed and rigid fixturing.
- Selection note
- 254SMO is often the most economical upgrade where 316L or duplex fails in hot chloride service, avoiding the jump to titanium or nickel alloys.
Buy 254SMO / Alloy 254 (6 Mo Super Austenitic) from Hangbo
Material is supplied with full heat-number traceability, solution annealing or ageing performed under calibrated furnace control, and an EN 10204 3.1 certificate covering chemical analysis, mechanical properties, heat treatment records and the agreed NDT scope. Positive material identification and third party inspection and test reports from SGS are available for critical service.
Request a quotation for 254SMO / Alloy 254 (6 Mo Super Austenitic)