ASTM A182 F6NM – UNS S41500
Forged 13Cr-4Ni-Mo soft martensitic stainless steel (wrought equivalent of CA6NM)
Low-carbon martensitic with 3.5–5.5% Ni and 0.5–1.0% Mo, which after tempering forms reverted austenite and reaches high toughness, good weldability and cavitation resistance. It is the wrought equivalent of cast CA6NM, standard in hydraulic turbines, pumps and oil and gas valves.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | S41500 |
| W.Nr./EN | 1.4313 (X3CrNiMo13-4) |
| DIN | X3CrNiMo13-4 |
| JIS | SCS6 (cast, approximate) |
| Trade names | 13-4, 13Cr4Ni, F6NM |
| Others | Cast: ASTM A743/A487 CA6NM; AISI 415 (plate) |
Standards by product form
| Form | Standard |
|---|---|
| Forging/flange | ASTM A182 / ASME SA-182 F6NM |
| Forging (vessels) | ASTM A336 F6NM |
| Bar | ASTM A479 / A276 (S41500) |
| Plate | ASTM A240 (S41500) |
| Tube | ASTM A268 (S41500) |
| Casting | ASTM A743 / A487 CA6NM |
Tolerances and HS codes
- Forged bars (round and square): machining allowance from 2 mm (Ø 6–16 mm) to 24 mm (Ø 400–500 mm) on the diameter. E.g. Ø 100–125 mm finished: +7 mm, tolerance +6 / −0 (length up to 3,500 mm).
- Forged discs: allowance of 4 to 9 mm on the diameter and 3 to 11 mm on the height, plus-only tolerance.
- Cutting and machining: band saw −0 / +5 to +15 mm on length; waterjet +10 % of thickness on the diameter (min. 2 mm); machined parts −0 / +2 to +5 mm on the diameter. See the full tables (INF 002 and INF 003, the same for every alloy).
| Form | NCM (Brazil, 8 digits) | HS (international, 6 digits) | HTS (USA, 10 digits)* | CN (European Union, 8 digits)* |
|---|---|---|---|---|
| Forged bar | 7222.30.00 | 7222.30 | 7222.30.0024 | 7222 30 51 |
| Hot-rolled bar | 7222.11.00 | 7222.11 | 7222.11.0059 | 7222 11 11 |
| Plate (> 10 mm, width ≥ 600 mm) | 7219.21.00 | 7219.21 | 7219.21.0020 | 7219 21 10 |
| Seamless pipe | 7304.41.90 | 7304.41 | 7304.41.6045 | 7304 41 00 |
| Welded pipe | 7306.40.00 | 7306.40 | 7306.40.5085 | 7306 40 80 |
| Flange and fitting | 7307.21.00 | 7307.21 | 7307.21.5000 | 7307 21 00 |
Tariff class: stainless steel (by chemical composition, under the Chapter 72 Notes and Section XV Note 5).
*: US and EU codes for reference. NCM per current legislation (General Rules of Interpretation, Notes to Chapters 72, 74 and 75 and Section XV Note 5). Confirm the final code with your customs broker according to the item size and finish. HS = first 6 digits of the NCM.
Chemical composition (%)
ASTM A182 F6NM
| Element | Range (%) |
|---|---|
| C | ≤ 0.05 |
| Mn | 0.50 – 1.00 |
| Si | ≤ 0.60 |
| P | ≤ 0.030 |
| S | ≤ 0.030 |
| Cr | 11.5 – 14.0 |
| Ni | 3.5 – 5.5 |
| Mo | 0.50 – 1.00 |
| Fe | balance |
Mechanical properties
Quenched and tempered (ASTM A182 F6NM)
| Property | Value |
|---|---|
| Yield strength (0.2%) | ≥ 620 MPa |
| Tensile strength | ≥ 790 MPa |
| Elongation | ≥ 15% |
| Reduction of area | ≥ 45% |
| Hardness | ≤ 295 HB |
| H2S service (NACE MR0175) | ≤ 23 HRC, double tempered |
Typical physical properties
| Property | Value |
|---|---|
| Density | 7.70 g/cm³ |
| Melting range | ≈ 1,450 – 1,510 °C (typical) |
| Modulus of elasticity | 200 GPa |
| Thermal conductivity (100 °C) | ≈ 25 W/m·K (typical) |
| Thermal expansion (20–100 °C) | ≈ 10.5 µm/m·K (typical) |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | Structural use from ≈ −50 °C (with qualified Charpy) up to ≈ 350 °C. |
| Heat treatment | Austenitize at 1,010 °C min., cool in air or liquid to below 95 °C; temper at 560–600 °C (ASTM A182). For NACE MR0175/ISO 15156: double tempering (≈ 670 °C + 600 °C) to ≤ 23 HRC. |
| Welding | Good for a martensitic grade: preheat 100–150 °C, interpass ≤ 250 °C, post-weld treatment 580–620 °C. Consumables AWS E410NiMo-15/-16 and ER410NiMo. |
| Machining | Fair to good in the tempered condition (≈ 250–290 HB); behavior close to hardened 410. |
Filler metal for welding
The wire composition is usually not identical to the material: each page explains why.
Typical applications
- Hydraulic turbine runners and blades (Francis, Pelton, Kaplan)
- Pump impellers and casings
- O&G valve bodies, bonnets and internals
- Water injection flanges and fittings
- Compressors and subsea equipment
- Parts subject to cavitation and erosion
Alternatives: 410/CA15 when toughness is not critical (cheaper); 431 for shafts with higher hardness; 17-4PH H1150D for higher strength; duplex 2205 (F51) when chlorides are present and the PREN of 13-4 is insufficient.
ASTM A182 F6NM: complete guide
What F6NM stainless steel is
F6NM belongs to the family of martensitic and ferritic stainless steels, in the soft martensitic group (13Cr-4Ni). F6NM is the forging designation in ASTM A182; the material itself is UNS S41500, equivalent to the European 1.4313 and the cast CA6NM. Carbon limited to 0.05% and nickel of 3.5 to 5.5% produce a low-carbon martensite, tough and weldable, with a small fraction of retained austenite that absorbs impact. Molybdenum, from 0.5 to 1.0%, is mandatory in the standard and improves temper resistance and corrosion resistance.
Mechanical properties
Normalized and tempered, ASTM A182 requires a minimum yield strength of 620 MPa, minimum tensile strength of 790 MPa, minimum elongation of 15%, minimum reduction of area of 45% and maximum hardness of 295 HBW. For H2S service, NACE MR0175 / ISO 15156 requires double tempering and a hardness of up to 23 HRC.
Corrosion, cavitation and limits of use
With a PREN of 14 to 17, F6NM resists fresh water, wet steam and CO2-bearing media, but is limited in chlorides. Its advantage lies in resistance to cavitation and erosion, superior to the martensitic 410 and CA15 (the equivalent casting, CA6NM, performs similarly), which makes it the standard for Francis and Pelton runners and high-head pumps.
Applications
Hydraulic turbine runners, blades and shafts, high-pressure pump casings and impellers, valve stems and bodies, wellhead and compressor components, forged parts for the energy and oil and gas sectors.
Supply forms and Dustre services
Round bars and blocks forged in open die, cut to size on a band saw, with rough or finish machining, heat treatment (quenching and tempering, annealing, solution annealing and aging) in our own furnaces and hardness, tensile and impact testing. All material is supplied with a 3.1 inspection certificate and heat traceability.
Frequently asked questions
What is the chemical composition of ASTM A182 F6NM?
Per ASTM A182 F6NM: C ≤ 0.05; Mn 0.50 – 1.00; Si ≤ 0.60; P ≤ 0.030; S ≤ 0.030; Cr 11.5 – 14.0.
Which standards cover ASTM A182 F6NM?
Forging/flange: ASTM A182 / ASME SA-182 F6NM. Forging (vessels): ASTM A336 F6NM. Bar: ASTM A479 / A276 (S41500). Plate: ASTM A240 (S41500). Tube: ASTM A268 (S41500). Casting: ASTM A743 / A487 CA6NM.
Up to what temperature can ASTM A182 F6NM be used?
Structural use from ≈ −50 °C (with qualified Charpy) up to ≈ 350 °C.
Which materials can replace ASTM A182 F6NM?
410/CA15 when toughness is not critical (cheaper); 431 for shafts with higher hardness; 17-4PH H1150D for higher strength; duplex 2205 (F51) when chlorides are present and the PREN of 13-4 is insufficient.
