ASTM A182 Grade F11 is a high-performance, low-alloy ferritic steel widely specified for the manufacture of forged flanges, fittings, valves, and other pressure-containing components intended for elevated-temperature and corrosive service. Bridging the operational gap between basic carbon steels and high-alloy stainless steels, Grade F11 leverages chromium and molybdenum additions to retain mechanical strength and resist creep deformation at continuous operating temperatures up to 480°C (900°F) and short-term exposures up to 550°C (1020°F).
The grade features deliberate silicon addition (0.50% - 1.00%), classifying it as a silicon-modified grade that provides elevated-temperature tensile strength and excellent scaling resistance in high-temperature air and steam atmospheres.
ASTM A182 F11 is divided into three classes (Class 1, 2, and 3) to accommodate varying strength and ductility requirements across pressure vessel and piping codes.
| ASTM Grade | UNS Designation | EN / DIN Standard | British (BS) / JIS Standard | Casting Equivalent |
|---|---|---|---|---|
| F11 Class 1 | K11597 | 1.7335 / 13CrMo4-5 | 3604 Gr. 11 / SCMV3 | ASTM A217 WC6 |
| F11 Class 2 | K11572 | 1.7335 / 13CrMo4-5 | 3604 Gr. 11 / SCMV3 | ASTM A217 WC6 |
| F11 Class 3 | K11572 | 1.7335 / 13CrMo4-5 | 3604 Gr. 11 / SCMV3 | ASTM A217 WC6 |
Chemical composition is tightly regulated to balance hardenability, weldability, and mechanical stability. Classes 2 and 3 permit higher carbon limits to achieve greater strength.
| Element | Class 1 (UNS K11597) | Class 2 & Class 3 (UNS K11572) |
|---|---|---|
| Carbon (C) | 0.05 – 0.15 | 0.10 – 0.20 |
| Manganese (Mn) | 0.30 – 0.60 | 0.30 – 0.80 |
| Phosphorus (P) | 0.030 max | 0.040 max |
| Sulfur (S) | 0.030 max | 0.040 max |
| Silicon (Si) | 0.50 – 1.00 | 0.50 – 1.00 |
| Chromium (Cr) | 1.00 – 1.50 | 1.00 – 1.50 |
| Molybdenum (Mo) | 0.44 – 0.65 | 0.44 – 0.65 |
| Nickel (Ni) | — | 0.40 max |
Contains empirical data for stress simulations, full thermal expansion charts, and advanced piping configuration tables. Corporate/engineering credentials required.
⬇ DOWNLOAD DATASHEETThe mechanical performance relies heavily on the final heat treatment state: annealed (Class 1) versus normalized and tempered (Classes 2 & 3).
| Mechanical Property | Class 1 (Annealed) | Class 2 (N & T) | Class 3 (N & T) |
|---|---|---|---|
| Tensile Strength, min | 60 ksi [415 MPa] | 70 ksi [485 MPa] | 75 ksi [515 MPa] |
| Yield Strength, min | 30 ksi [205 MPa] | 40 ksi [275 MPa] | 45 ksi [310 MPa] |
| Elongation in 2 in. / 50mm | 20% | 20% | 20% |
| Reduction of Area | 45% | 30% | 30% |
| Brinell Hardness (HBW) | 121 – 174 | 143 – 207 | 156 – 207 |
Grade F11 is a strongly ferromagnetic low-alloy steel. Its density is approximately 7.85 g/cm³ with a melting range of 1371°C to 1480°C (2500°F to 2700°F). Relevant high-temperature properties used for thermodynamic calculations are abbreviated below:
| Temperature | Mean Thermal Expansion (10⁻⁶ mm/mm·°C) |
Thermal Conductivity (W/m·°C) |
Modulus of Elasticity (10³ MPa) |
|---|---|---|---|
| 20°C (68°F) | 11.5 | 41.0 | 204 |
| 200°C (392°F) | 12.7 | 40.1 | 193 |
| 400°C (752°F) | 13.8 | 36.8 | 179 |
| 600°C (1112°F) | 14.8 | 32.8 | 157 |
As temperatures rise, the allowable working pressure drops significantly due to yield strength reduction and the onset of creep.
| Service Temp (°F) | Service Temp (°C) | Max Allowable Working Pressure (psig) |
|---|---|---|
| -20 to 100 | -29 to 38 | 290 |
| 400 | 204 | 200 |
| 600 | 316 | 140 |
| 800 | 427 | 80 |
| 1000 | 538 | 20 |
Grade F11 exhibits strong air-hardening tendencies. Rapid cooling rates promote hard, brittle acicular martensite, demanding strict thermal controls during welding.
| Parameter | Specification Criteria | Metallurgical Objective |
|---|---|---|
| ASME Group / P-Number | P-No. 4, Group 1 | Classifies low-alloy steels (1% ≤ Cr ≤ 2%). |
| Filler Metal | AWS A5.28 ER80S-B2 | Matches the 1.25% Cr - 0.5% Mo base chemistry. |
| Minimum Preheat Temp. | 150°C - 200°C (300°F - 400°F) | Retards cooling to prevent martensite formation. |
| PWHT Temperature Range | 650°C - 705°C (1200°F - 1300°F) | Relieves residual stresses and restores ductility. |
| Hardness Limit (NACE) | 22 HRC max (237 HBW max) | Prevents sulfide stress cracking in sour service. |
