Bar and Rod
Plate and Sheet
Strip
Pipe and Tube
Wire
Welding
Powder Material
Cast Products
Forged Products
Fittings
Fastening
Round Bar:
φ2–500 mm, 1–6 m length
Flat/Square Bar:
4–100 mm thickness/width
Hex Bar:
A/F 3–100 mm
Hollow Bar:
OD 20–300 mm
Sheet:
0.3–6 mm thickness
Medium Plate:
6–25 mm thickness
Heavy Plate:
25–100 mm thickness
Standard Strip:
0.05–3 mm thick,
10–600 mm wide
Precision strip:
0.01–0.5 mm thick,
tight tolerance ±0.005 mm
Foil:
0.005–0.1 mm thick
Seamless Tube:
OD 6–450 mm,
WT 1–50 mm,
1–12 m length
Welded Tube:
OD 10–600 mm,
WT 1–20 mm
Capillary Tube:
OD 1–10 mm,
WT 0.1–2 mm
Wire Form:
Cold Drawn Wire,
Bright Wire,
Spring Wire,
Fine Wire,
Ultra-fine Wire
General Diameter:
φ0.1–10 mm
Coil Weight:
50–500 kg,
customizable tolerance
Solid Wire:
φ0.8–4.0 mm
Flux-cored Wire:
φ1.2–4.0 mm
Welding Rod:
φ2.0–5.0 mm
Powder Form:
AM 3D Printing Powder,
Spherical Powder,
Gas-atomized Powder,
Water-atomized Powder
Particle Size:
10–150 μm
Sphericity:
≥90% for AM grade
Cast Ingot:
φ200–800 mm
Precision Casting:
min wall 0.5 mm
Cast Pipe:
OD 100–600 mm,
WT 10–50 mm
Forged Bar:
Φ35–500 mm
Forged Ring:
OD 200–2000 mm
Forging Weight:
1–5000 kg
Fittings Form:
Elbow, Tee, Reducer, Flange, Cap, Outlet, Lap Joint
Size range:
1/2''–24'' (DN15–DN600)
Wall thickness:
Sch10–Sch160, STD, XS, XXS
Pressure Class:
150–2500 LB
Fastening Form:
Bolt, Nut, Screw, Stud, Washer, Pin, Rivet
Metric: M3–M64
Imperial: #4–2.5''
Length: 6–500 mm
F44 is a 6% molybdenum super-austenitic stainless steel, originally developed for service in seawater and other aggressive chloride-bearing environments. This datasheet presents the material within the American standard system.
The specific high levels of chromium, nickel, molybdenum and nitrogen in this super-austenitic composition give it outstanding resistance to pitting and crevice corrosion (Pitting Resistance Equivalent Number, PREN, of about 42-44), very high resistance to chloride stress-corrosion cracking, and good resistance to general and sulphide-stress corrosion. It combines this with impact toughness and high ductility at both ambient and sub-zero temperatures, and a strength nearly twice that of the standard 300-series austenitic grades. The high molybdenum and nitrogen make it a cost-effective alternative to far more expensive high-nickel alloys and titanium in many chloride process streams. It is fully austenitic and essentially non-magnetic, and cannot be hardened by heat treatment (strength is raised only by cold work).
Typical applications include seawater and brackish-water handling, desalination equipment, flue-gas-desulphurization scrubbers, food and chemical processing equipment, petroleum production, tall-oil distillation columns, pulp-mill bleach systems, and offshore oil-and-gas production equipment.
Values per manufacturer / reference data, solution-annealed condition.
| Property | Value | Unit |
|---|---|---|
| Density | 8.0 | g/cm³ |
| Melting range | 1325–1400 | °C |
| Young's modulus (20 °C) | 195 | GPa |
| Thermal conductivity (20 °C) | ~14 | W/m·K |
| Coefficient of thermal expansion (20–100 °C) | ~16.5 | µm/m·°C |
| Electrical resistivity (20 °C) | ~0.85 | µΩ·m |
| PREN (Cr + 3.3×Mo + 16×N) | 42–44 | — |
| Magnetic response | Non-magnetic (austenitic) | — |
Limiting composition per ASTM A240.
| Element | Symbol | Min % | Max % | Role in Alloy |
|---|---|---|---|---|
| Iron | Fe | Balance | — | Base element |
| Chromium | Cr | 19.5 | 20.5 | Passivity; pitting resistance |
| Nickel | Ni | 17.5 | 18.5 | Austenite stability; SCC resistance |
| Molybdenum | Mo | 6.0 | 6.5 | Pitting + crevice corrosion resistance |
| Copper | Cu | 0.5 | 1.0 | Resistance to reducing acids |
| Nitrogen | N | 0.18 | 0.22 | Pitting resistance; strength; austenite stability |
| Manganese | Mn | — | 1.0 | Austenite stabiliser |
| Silicon | Si | — | 0.8 | Deoxidiser |
| Carbon | C | — | 0.020 | Very low (intergranular-corrosion resistance) |
| Phosphorus | P | — | 0.030 | Residual impurity |
| Sulphur | S | — | 0.010 | Residual impurity |
Nominal: 20Cr-18Ni-6.1Mo-Cu-N. PREN (Cr + 3.3×Mo + 16×N) of about 42-44 gives super-austenitic localized-corrosion resistance superior to 904L and the 4.5Mo grades.
Minimum room-temperature properties, solution-annealed condition.
| Property | Value | Source |
|---|---|---|
| Ultimate tensile strength | ≥650 MPa (94 ksi) | ASTM A240 |
| 0.2% proof strength (yield) | ≥300 MPa (44 ksi) | ASTM A240 |
| Elongation at break | ≥35 % | ASTM A240 |
| Hardness | ≤223 HB / ≤96 HRB | ASTM A240 |
Strength is nearly twice that of the 300-series austenitic grades, aided by the nitrogen addition; impact toughness and ductility are excellent at ambient and sub-zero temperatures. Values are specified minima; confirm against the mill test certificate.
| Environment | Performance | Notes |
|---|---|---|
| Pitting (chlorides) | Outstanding | PREN 42–44; superior to 904L |
| Crevice corrosion | Outstanding | Resistant in seawater |
| Chloride SCC | Excellent | High Ni content |
| Seawater / brackish water | Excellent | Original design purpose |
| Sulphide stress corrosion | Good | — |
| Erosion-corrosion | Good | — |
| ASTM G48A pitting test (50 °C) | Passes | No pitting; <4.0 g/m² loss |
| Hot oxidising / high temperature | Limited | A corrosion alloy, not a heat-resistant alloy |
A super-austenitic stainless steel; not hardenable by heat treatment (strengthened only by cold work). Corrosion properties are developed by solution annealing.
Solution Anneal approximately 1149–1204 °C (2100–2200 °F), followed by rapid quenching in water, to dissolve secondary phases (e.g. sigma) and put molybdenum and nitrogen into solution for optimum corrosion resistance.
Because the high Mo content makes the alloy susceptible to precipitation of intermetallic phases on slow cooling, rapid cooling from the annealing temperature is essential. Heat treatment after hot forming is required to restore optimum corrosion resistance.
Has excellent weldability. To avoid molybdenum depletion in the weld and maintain corrosion resistance, an over-alloyed nickel-base filler is used rather than matching composition — typically AWS A5.14 ERNiCrMo-3 (alloy 625 type) bare wire, with AWS A5.11 ENiCrMo-3/-12 electrodes for SMAW.
| Process | Applicability | Filler / Consumable |
|---|---|---|
| GTAW / TIG · GMAW | Excellent | Over-alloyed Ni-base |
| SMAW | Good | ENiCrMo-3 / ENiCrMo-12 electrodes |
| Filler-less | Avoid | Loses strength/corrosion resistance |
No preheat required; control heat input. Over-alloyed filler compensates for weld-metal segregation.
Machining Guidelines
| Parameter | Recommendation |
|---|---|
| Machinability | Tough; high work-hardening rate, low sulphur; sharp tools, overpowered machines |
| Speed / feed | Slow speeds, positive (heavy) feeds, ample lubrication |
| Work hardening | Very high; rigid setup |
| Coolant | Ample flood coolant |
Forming Processes
| Process | Notes |
|---|---|
| Hot working | ~1150–1200 °C; solution anneal + quench after |
| Cold forming | Readily formed; work-hardens (raises surface hardness) |
| Solution anneal | 1149–1204 °C, water quench |
| Industry | Typical Components | Key Requirements |
|---|---|---|
| Marine / desalination | Seawater piping, desalination equipment, condensers | Chloride pitting/crevice resistance |
| Power | Flue-gas-desulphurization scrubbers, ducting | Halide + acid resistance |
| Chemical / food | Process equipment, tanks, heat exchangers | Corrosion resistance |
| Pulp & paper | Bleach-plant equipment | Halide / bleach resistance |
| Oil & gas | Offshore production equipment, tall-oil columns | Pitting + SCC resistance |
| Petroleum | Petroleum-production equipment | Chloride corrosion resistance |
| Product Form | ASTM | ASME |
|---|---|---|
| Plate, sheet and strip | ASTM A240 | ASME SA-240 |
| Bar | ASTM A276 / A479 | ASME SA-479 |
| Forgings and fittings | ASTM A182 | ASME SA-182 |
| Seamless / welded pipe and tube | ASTM A312 / A358 | ASME SA-312 |
| Wire | ASTM A580 | — |
Super-austenitic 6Mo stainless steel. UNS S31254; ASTM A240 / A182 / A276 / A479 / A312. Tradenames: 254 SMO, Alloy 254, F44, 6Mo.
| F44 | Nominal | PREN | Best Used For |
|---|---|---|---|
| F44 | 20Cr-18Ni-6.1Mo-Cu-N | 42–44 | Seawater 6Mo; highest-Ni/Mo super-austenitic |
| N08926 | 25Ni-20Cr-6.5Mo-Cu-N | 38–43 | 6Mo with higher Ni content |
| N08367 | 24Ni-21Cr-6.3Mo-N | 40–45 | 6Mo (US; no Cu) |
| N08904 | 25Ni-20Cr-4.5Mo-Cu | ~34 | Acid service (lower Mo) |
| S31603 | 12Ni-17Cr-2.1Mo | ~24 | General stainless (reference) |
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