ASTM A182 F11 Class 2 – UNS K11572
Forged 1¼Cr-½Mo steel for steam and elevated temperature
Cr-Mo steel with 1.0–1.5% Cr and 0.5% Mo, forged to ASTM A182, in three strength classes (Cl.1, Cl.2 and Cl.3). Class 2 is the most traded for flanges and fittings of steam and refinery lines up to ≈ 550 °C.
Designations and equivalents
| System | Designation |
|---|---|
| UNS | K11572 (Cl.2/3); K11597 (Cl.1) |
| W.Nr./EN | ≈ 13CrMo4-5 – 1.7335 (EN 10222-2) |
| DIN | 13CrMo44 (old) |
| JIS | SFVAF11A (JIS G3203) |
| Trade names | 1¼Cr-½Mo, F11 |
| Others | Pipe A335 P11; plate A387 Gr 11; fittings A234 WP11; casting A217 WC6 |
Standards by product form
| Form | Standard |
|---|---|
| Forging (flanges, fittings, valves) | ASTM A182/A182M F11 Cl.1/2/3; ASME SA-182 |
| Larger forgings | ASTM A336 F11 |
| Pipe/tube | ASTM A335 P11 / A213 T11 |
| Plate | ASTM A387 Gr 11 |
| Butt-welding fittings | ASTM A234 WP11 |
| Casting | ASTM A217 WC6 |
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 – F11 Class 2 (Cl.1: C 0.05–0.15; Mn 0.30–0.60; P, S ≤ 0.030)
| Element | Range (%) |
|---|---|
| C | 0.10 – 0.20 |
| Mn | 0.30 – 0.80 |
| P | ≤ 0.040 |
| S | ≤ 0.040 |
| Si | 0.50 – 1.00 |
| Cr | 1.00 – 1.50 |
| Mo | 0.44 – 0.65 |
Mechanical properties
Normalized + tempered – ASTM A182 F11 (Cl.1 / Cl.2 / Cl.3)
| Property | Value |
|---|---|
| Yield strength (0.2%) | Cl.1 ≥ 205 / Cl.2 ≥ 275 / Cl.3 ≥ 310 MPa |
| Tensile strength | Cl.1 ≥ 415 / Cl.2 ≥ 485 / Cl.3 ≥ 515 MPa |
| Elongation | ≥ 20% |
| Reduction of area | Cl.1 ≥ 45% / Cl.2 and 3 ≥ 30% |
| Hardness | Cl.1 121–174 / Cl.2 143–207 / Cl.3 156–207 HBW |
Typical physical properties
| Property | Value |
|---|---|
| Density | 7.85 g/cm³ |
| Modulus of elasticity | ≈ 205 GPa |
| Thermal conductivity (20 °C) | ≈ 41 W/m·K (typical) |
| Thermal expansion (20–100 °C) | ≈ 11.9 µm/m·K (typical) |
Heat treatment, welding and machining
| Item | Usual practice |
|---|---|
| Service temperature | Up to ≈ 550–595 °C in continuous service (creep); ASME allows up to 649 °C with reduced stresses. |
| Heat treatment | Annealing or normalizing (≈ 900–960 °C) + tempering ≥ 620 °C (usually 650–730 °C). Cl.3 may be quenched and tempered. |
| Welding | Preheat ≈ 150 °C, consumable AWS E8018-B2 / E8015-B2 (A5.5), ER80S-B2 (A5.28); PWHT ≈ 650–730 °C according to thickness and code. |
| Machining | Good in the normalized and tempered condition. |
Filler metal for welding
The wire composition is usually not identical to the material: each page explains why.
Typical applications
- Flanges and fittings for boiler and power plant steam lines
- Hot refinery and petrochemical piping
- Steam valve bodies
- Vessel and exchanger nozzles in A387 Gr 11
- Moderate hydrogen service (Nelson)
Alternatives: F22 for higher temperature/pressure; F1 is obsolete for the same use; A105 below ≈ 425 °C; F91 for supercritical power plants.
ASTM A182 F11 Class 2: complete guide
What ASTM A182 F11 steel is
F11 is the first chromium-molybdenum grade in the ASTM A182 series of high-temperature alloy steels, above F1 (C-½Mo) and below F22 (2¼Cr-1Mo). It is the forged version of A335 P11 pipe. It exists in three classes with the same chemical base and different strength levels; Class 2 is the most used.
Chemical composition and role of the elements
Chromium (1.00 – 1.50%) improves resistance to oxidation by steam and stabilizes the carbides; molybdenum (0.44 – 0.65%) increases creep resistance. There is no "sum of alloying elements up to 6%" rule: the 5% limit that separates low- and high-alloy steels is only a classification convention, with no normative value.
Mechanical properties
In the normalized and tempered condition Class 2 requires a minimum yield strength of 275 MPa, minimum tensile strength of 485 MPa, minimum elongation of 20%, minimum reduction of area of 30% and hardness between 143 and 207 HBW. Class 1 is softer (UTS ≥ 415 MPa) and Class 3 stronger (UTS ≥ 515 MPa).
Heat treatment
Normalizing and tempering, or quenching and tempering, with a minimum tempering temperature of 620 °C. Dustre performs the cycle in its own furnaces, with temperature records, as part of its heat treatment service.
Applications
Flanges, fittings, valves and headers for steam lines, boilers and low-temperature superheaters, refinery and petrochemical vessels and piping up to about 550 °C. It is not a material for surgical instruments, springs or automotive parts: those applications use other steels.
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 F11 Class 2?
Per ASTM A182/A182M – F11 Class 2 (Cl.1: C 0.05–0.15; Mn 0.30–0.60; P, S ≤ 0.030): C 0.10 – 0.20; Mn 0.30 – 0.80; P ≤ 0.040; S ≤ 0.040; Si 0.50 – 1.00; Cr 1.00 – 1.50.
Which standards cover ASTM A182 F11 Class 2?
Forging (flanges, fittings, valves): ASTM A182/A182M F11 Cl.1/2/3; ASME SA-182. Larger forgings: ASTM A336 F11. Pipe/tube: ASTM A335 P11 / A213 T11. Plate: ASTM A387 Gr 11. Butt-welding fittings: ASTM A234 WP11. Casting: ASTM A217 WC6.
Up to what temperature can ASTM A182 F11 Class 2 be used?
Up to ≈ 550–595 °C in continuous service (creep); ASME allows up to 649 °C with reduced stresses.
Which materials can replace ASTM A182 F11 Class 2?
F22 for higher temperature/pressure; F1 is obsolete for the same use; A105 below ≈ 425 °C; F91 for supercritical power plants.
