ASTM A182 F44 Forgings, UNS S31254 / 254 SMO / EN 1.4547
Forged rings, seamless rolled rings, flanges, shafts, bars, discs and tube sheets in 6% molybdenum super austenitic stainless steel, made to drawing by Jiangyin Jiangnan Metal Co., Ltd.
- Grade
- ASTM A182 Grade F44
- Other designations
- UNS S31254, EN 1.4547, 254 SMO, 6Mo
- EN steel name
- X1CrNiMoCuN20-18-7
- Alloy family
- Super austenitic, non-magnetic
- PREN, calculated
- About 42 to 43
- Melting route
- EAF plus AOD or VOD, ESR on request
- Certification
- EN 10204 3.1, or 3.2 third party
ASTM A182 Grade F44 is the forging grade of UNS S31254. The alloy carries about 20% chromium, 18% nickel, 6% molybdenum and 0.18 to 0.25% nitrogen. That combination holds up to pitting and crevice attack in chloride service where 316L fails, and the yield strength runs well above the 300 series. Buyers see the same material sold as 254 SMO, 6Mo or EN 1.4547.
We forge F44 on open dies and roll it into seamless rings, working to customer drawings. Usual items are rings, flanges, round bars, shafts, discs, blanks, sleeves, bushings, tube sheets, nozzles, valve bodies and valve seat rings.
Chemical composition of ASTM A182 F44 (UNS S31254)
| C | Mn | P | S | Si | Cr | Ni | Mo | Cu | N |
|---|---|---|---|---|---|---|---|---|---|
| 0.020 max | 1.00 max | 0.030 max | 0.010 max | 0.80 max | 19.50–20.50 | 17.50–18.50 | 6.00–6.50 | 0.50–1.00 | 0.18–0.25 |
Weight percent, limits for A182 F44. Two points to watch. Published sulfur limits differ between sources, 0.010% and 0.10%. And the wider EN 1.4547 specification is sometimes quoted with molybdenum 6.0 to 7.0% rather than the 6.00 to 6.50% listed for A182 F44. Check the governing edition of ASTM A182 before fixing acceptance values on an order.
Nitrogen is the element most often left off supplier data sheets for this grade, and it is the one that matters. Together with chromium and molybdenum it is what lifts the pitting resistance equivalent number into super duplex territory. Nitrogen appears on every mill certificate we issue.
PREN calculation
The pitting resistance equivalent number is calculated as PREN = %Cr + 3.3 × %Mo + 16 × %N. Taking the minimum grade limits, 19.5% chromium, 6.00% molybdenum and 0.18% nitrogen, the result is about 42.2. On a typical mill analysis of 20% chromium, 6.1% molybdenum and 0.20% nitrogen it comes out at about 43.3. Either figure sits in the range normally associated with super duplex stainless steels.
Mechanical properties, ASTM A182 F44 acceptance values
| Property | Imperial | Metric |
|---|---|---|
| Tensile strength, min | 94 ksi | 650 MPa |
| Yield strength, 0.2% offset, min | 44 ksi | 300 MPa |
| Elongation in 2 in. [50 mm] or 4D, min | 35% | 35% |
| Reduction of area, min | 50% | 50% |
Room temperature, solution annealed condition. Suppliers commonly quote an actual tensile range of 650 to 850 MPa for material in this condition.
Typical physical properties
| Property | Value |
|---|---|
| Density | 8.0 g/cm³ (0.289 lb/in³) |
| Modulus of elasticity at 20 °C | 195 to 200 GPa |
| Thermal conductivity at 20 °C | 13 to 14 W/m·K |
| Thermal expansion, 20 to 100 °C | 16.5 × 10⁻⁶ /°C |
| Specific heat at 20 °C | 500 J/kg·K |
| Electrical resistivity at 20 °C | 0.85 µΩ·m |
| Hardness, Brinell | about 250 HB, commonly capped at 260 HB max |
Physical property figures vary slightly between published mill data sheets, so ranges are shown rather than single values. Hardness limits should be taken from the purchase specification.
Heat treatment, forging and fabrication
Solution annealing
Solution anneal at 1150 to 1200 °C, then water quench. Cooling has to be fast through the sigma phase range. Slow cooling throws out intermetallic phases and the corrosion resistance goes with them.
Hot working
Forge and upset at roughly 982 to 1149 °C. Above that range the material scales heavily and loses workability. Re-solution anneal and quench after hot work to bring the corrosion resistance back.
Hardening
F44 does not respond to hardening heat treatment. Higher strength comes from cold reduction only, and the work hardening rate makes that heavy going.
Machining
Machining is slow. The alloy work hardens fast and has no free-machining sulfur. Rigid machines with power in reserve, sharp tools, positive feeds, reduced speeds and plenty of coolant. The approach is the same as 300 series stainless, applied more conservatively.
Welding
Use over-alloyed nickel-base consumables. Matching filler leaves weld metal short of molybdenum and the weld corrodes before the parent material does. AWS A5.14 ERNiCrMo-3 filler wire, alloy 625 type, and AWS A5.11 ENiCrMo-12 type electrodes are the standard choices.
F44 against 316L and super duplex
Against 316L, F44 buys a large gain in chloride pitting and crevice resistance along with higher yield strength. Against high nickel alloys and titanium it has been reported as a cheaper substitute in seawater and chemical service. Against super duplex grades such as F53 and F55 the PREN figures are close, but F44 stays austenitic, so it remains non-magnetic, keeps good toughness at low temperature, and avoids the phase balance and section thickness issues that come with a duplex structure. Super duplex still wins on yield strength. Which way to go depends on whether the governing requirement is strength per unit weight or simpler metallurgy in heavy sections.
Forged products we supply in A182 F44
Seamless rolled rings
Rolled rings and forged rings for seawater cooled plant, offshore modules and rotating equipment.
Flanges and tube sheets
Forged flanges, tube sheets, nozzles and shell sections for heat exchangers and separators.
Shafts, spindles and bars
Forged shafts, eccentric shafts, spindles, crankshafts and round bars for pumps and compressors.
Discs, blanks and sleeves
Forged discs, blanks, sleeves, bushings and gear blanks for power transmission.
Valve components
Valve bodies, stems, seat rings and blocks for ball, gate, globe, check and plug valves.
Pipe and pressure parts
Forged pipe, forged tube, manifolds and pressure containing parts for subsea systems.
Typical applications
Seawater handling and desalination, covering high pressure reverse osmosis plant, seawater piping, condensers and coolers. Offshore and subsea oil production, covering firewater and seawater systems, risers, manifolds and deepwater production hardware. Flue gas desulfurization and power plant scrubber systems, and marine exhaust gas cleaning. Chemical plant handling sulfuric acid, organic acids, mixed acids and chloride bearing media at raised pressure and temperature. Pulp and paper bleaching equipment and tall oil distillation columns. Also heat exchangers, waste water, demineralized water and polycarbonate production.
Quality, testing and certification
Material is melted by EAF plus AOD or VOD, with ESR refining where the specification or the end user calls for it. Ultrasonic examination to EN 10228-3, SEP 1921 or ASTM A388 as required. Standard paperwork is an EN 10204 3.1 inspection certificate; 3.2 third party certification through DNV, BV, LR, TUV, ABS and others is available on request. Supplementary testing on request covers PMI, ASTM G48 pitting test, intergranular corrosion test to ASTM A262, ferrite content, impact testing, hardness survey and dimensional report.
The same alloy is supplied under its other designations, 254 SMO forgings, UNS S31254 forged material and 1.4547 forged parts. Related grades we forge include A182 F51, F53, F55, F61, 904L, Alloy 20 and Alloy 31.
Frequently asked questions
Is A182 F44 the same as 254 SMO?
Yes. ASTM A182 F44, UNS S31254, EN 1.4547 and 254 SMO all describe the same 6% molybdenum super austenitic stainless steel. F44 is the designation used for forgings under ASTM A182. 254 SMO is a trade name. The EN steel name is X1CrNiMoCuN20-18-7.
Is F44 duplex or austenitic?
Fully austenitic and non-magnetic. The calculated PREN of roughly 42 to 43 matches super duplex levels, but the microstructure is not duplex. The duplex and super duplex forging grades are F51, F60, F53, F55 and F61.
What size can you forge?
Open-die forgings and seamless rolled rings to customer drawings across a wide size and weight range. Send the drawing or the finished dimensions with the governing standard and we will confirm feasibility, forging ratio and weight with the quotation.
Can F44 be used in sulfuric acid service?
It is used in chemical plant where resistance to pure acids and to acids carrying chloride ions, sulfuric acid in particular, is needed at raised pressure and temperature. Limits depend on concentration, temperature and what else is in the stream, so each case needs reviewing on its own figures.
What do you need to quote?
A drawing or the rough and finished dimensions, the quantity, the governing standard, the certificate level wanted under EN 10204, and any supplementary NDT or corrosion testing.
Request a quotation for A182 F44 forgings
Jiangyin Jiangnan Metal Co., Ltd., open-die forging factory
No.1 Chengxiqiao Road, Zhouzhuang Town, Jiangyin City, Jiangsu Province, China
Tel: +86-189-2135-9659
Email: sales@steelforgepieces.com. Send the drawing or the sizes and we will price it.
Technical data compiled from the ASTM A182 / A182M grade F44 requirements and published 254 SMO, UNS S31254 and 1.4547 mill data. Where published sources differ, ranges are shown. Data sheet revised . Figures are for guidance; the purchase specification governs.