ASTM A182 F9 – UNS K90941
Forged 9Cr-1Mo steel for high temperature and sulfidizing media
Cr-Mo steel with 8–10% Cr and 1% Mo, forged to ASTM A182. It has oxidation and sulfidation resistance superior to F5 and is used in furnaces and hot refinery lines. For high pressure/creep, the modified grade F91 (with V, Nb, N) has replaced it in many applications.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | K90941 |
| W.Nr./EN | X11CrMo9-1 – 1.7386 (EN 10216-2 / 10222-2) |
| DIN | X12CrMo9-1 (X12CrMo91, old) |
| JIS | SFVAF9 (JIS G3203) |
| Trade names | 9Cr-1Mo, F9 |
| Others | Pipe A335 P9; plate A387 Gr 9; fittings A234 WP9; casting A217 C12 |
Standards by product form
| Form | Standard |
|---|---|
| Forging (flanges, fittings, valves) | ASTM A182/A182M F9; ASME SA-182 |
| Larger forgings | ASTM A336 F9 |
| Pipe/tube | ASTM A335 P9 / A213 T9 |
| Plate | ASTM A387 Gr 9 |
| Butt-welding fittings | ASTM A234 WP9 |
| Casting | ASTM A217 C12 |
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 | 7228.40.00 | 7228.40 | 7228.40.0000 | 7228 40 90 |
| Plate (> 10 mm, width ≥ 600 mm) | 7225.40.90 | 7225.40 | 7225.40.3050 | 7225 40 40 |
| Seamless pipe | 7304.19.00 | 7304.19 | 7304.19.5050 | 7304 19 10 |
| Welded pipe | 7306.19.00 | 7306.19 | 7306.19.5150 | 7306 19 00 |
| Flange and fitting | 7307.91.00 | 7307.91 | 7307.91.5030 | 7307 91 00 |
Tariff class: alloy steel (by chemical composition, under the Chapter 72 Notes and Section XV Note 5).
Pipe: 7304.19 and 7306.19 are line pipe for oil and gas pipelines; boiler, heat exchanger or process tubes go under 7304.39/7304.59 (seamless) and 7306.30/7306.50 (welded).
*: 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/A182M – F9
| Element | Range (%) |
|---|---|
| C | ≤ 0.15 |
| Mn | 0.30 – 0.60 |
| P | ≤ 0.030 |
| S | ≤ 0.030 |
| Si | 0.50 – 1.00 |
| Cr | 8.0 – 10.0 |
| Mo | 0.90 – 1.10 |
Mechanical properties
Annealed or normalized + tempered – ASTM A182 F9
| Property | Value |
|---|---|
| Yield strength (0.2%) | ≥ 380 MPa |
| Tensile strength | ≥ 585 MPa |
| Elongation | ≥ 20% |
| Reduction of area | ≥ 40% |
| Hardness | 179 – 217 HBW |
Typical physical properties
| Property | Value |
|---|---|
| Density | 7.75 g/cm³ (typical) |
| Modulus of elasticity | ≈ 210 GPa (typical) |
| Thermal conductivity (20 °C) | ≈ 27 W/m·K (typical) |
| Thermal expansion (20–100 °C) | ≈ 10.9 µm/m·K (typical) |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | Up to ≈ 650 °C (ASME); oxidation limit ≈ 650 °C. |
| Heat treatment | Full annealing or normalizing (≈ 950–1,000 °C) + subcritical tempering ≥ 675 °C. |
| Welding | Air hardening: preheat 200–300 °C, consumable AWS E8018-B8 / E8015-B8 (A5.5), ER80S-B8 (A5.28); PWHT mandatory ≈ 730–790 °C. Do not use CE (IIW) as a criterion for 9Cr. |
| Machining | Fair; harder than F11/F22 because of the higher hardness. |
Filler metal for welding
The wire composition is usually not identical to the material: each page explains why.
Typical applications
- Refinery furnace flanges and fittings
- Transfer lines of distillation and coking units
- Valves for hot sulfidizing oil
- High-temperature hydrogen service (Nelson curves)
- Furnace and boiler tubes
Alternatives: F5 in less severe service at lower cost; F91 for creep and high pressure (higher strength); 316/317L stainless for naphthenic acids; 321/347 for severe H2S.
ASTM A182 F9: complete guide
What ASTM A182 F9 steel is
F9 is the grade with the highest chromium content among the conventional Cr-Mo alloy steels of ASTM A182, above F5 and F22. It is the forged version of A335 P9 pipe. Its density and weight are those of any steel; the advantage lies in resistance to oxidation and sulfur at high temperature, not in lightness or aqueous corrosion resistance.
Chemical composition and role of the elements
The 8 – 10% chromium forms a protective oxide layer stable up to about 650 °C; molybdenum increases creep resistance. Silicon, between 0.50 and 1.00%, reinforces oxidation resistance. Unlike F91, F9 has no vanadium, niobium or nitrogen, which is why its creep allowable stresses are much lower.
Mechanical properties
In the annealed or normalized and tempered condition the standard requires a minimum yield strength of 380 MPa, minimum tensile strength of 585 MPa, minimum elongation of 20%, minimum reduction of area of 40% and hardness between 179 and 217 HBW.
Heat treatment
Annealing or normalizing and tempering, with a minimum tempering temperature of 675 °C. Dustre performs the cycle in its own furnaces, with temperature records, as part of its heat treatment service.
Applications
Refinery and petrochemical furnaces, hot transfer lines, valves and flanges of hydrotreating and cracking units, heat exchangers with sulfurous fluids. For steam components in severe creep regime, F91 is the choice.
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 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 F9?
Per ASTM A182/A182M – F9: C ≤ 0.15; Mn 0.30 – 0.60; P ≤ 0.030; S ≤ 0.030; Si 0.50 – 1.00; Cr 8.0 – 10.0.
Which standards cover ASTM A182 F9?
Forging (flanges, fittings, valves): ASTM A182/A182M F9; ASME SA-182. Larger forgings: ASTM A336 F9. Pipe/tube: ASTM A335 P9 / A213 T9. Plate: ASTM A387 Gr 9. Butt-welding fittings: ASTM A234 WP9. Casting: ASTM A217 C12.
Up to what temperature can ASTM A182 F9 be used?
Up to ≈ 650 °C (ASME); oxidation limit ≈ 650 °C.
Which materials can replace ASTM A182 F9?
F5 in less severe service at lower cost; F91 for creep and high pressure (higher strength); 316/317L stainless for naphthenic acids; 321/347 for severe H2S.
