ASTM A182 F11 Alloy Steel Flanges – A182 Gr F11 Cr-Mo Flanges to ASME B16.5
ASC LLP, Mumbai, supplies ASTM A182 F11 flanges: forged 1¼Cr-½Mo alloy steel weld neck, slip-on, blind, socket-weld and RTJ flanges to ASME B16.5 and B16.47, in Class 150 to 2500. In addition, every flange carries an EN 10204 3.1 certificate stating the F11 class, heat treatment and test results. See also our full range of alloy steel flanges.
What are ASTM A182 F11 Flanges?
ASTM A182 (ASME SA182) covers forged or rolled alloy and stainless steel pipe flanges, forged fittings and valve parts for high-temperature service. Grade F11 is a 1¼% chromium – ½% molybdenum steel with added silicon. As a result, F11 flanges keep their strength and resist oxidation in steam service, so they are the standard flange for P11 Cr-Mo piping.
F11 is supplied in Class 1, 2 or 3, and the class decides the flange rating. For this reason, F11 flanges are normally ordered as F11 Class 2, which is listed in ASME B16.5 Material Group 1.9. For the full F11 chemistry and material data, see our A182 F11 fittings page.
A182 F11 Flanges – Quick Facts
- Specification: ASTM A182 / ASME SA182, Grade F11 Class 1, 2 or 3
- Material: 1¼Cr-½Mo-Si alloy steel, forged
- Standards: ASME B16.5 (NPS ½–24), B16.47 Series A/B (NPS 26–60)
- Pressure class: 150, 300, 600, 900, 1500 and 2500
- B16.5 group: 1.9 (F11 Class 2)
- Matching pipe: ASTM A335 P11
A182 F11 Flange Types
- Weld neck (WN): the preferred flange for high-temperature P11 lines, because the tapered hub spreads stress.
- Slip-on (SO): for lower-pressure lines where fillet welding is acceptable.
- Blind (BL): to close pipe ends and vessel nozzles.
- Socket weld (SW) and threaded: for small-bore lines up to NPS 2–3.
- Long weld neck, orifice and spectacle blinds: also supplied to drawing on request.
- Facings: raised face (RF), flat face (FF) and ring type joint (RTJ).
Why the F11 Class Matters for Flanges
ASME B16.5 rates flanges by material group. F11 Class 2 is listed in Group 1.9, together with A217 WC6 castings and A387 Grade 11 Class 2 plate, so its pressure–temperature rating is taken from that group. In other words, a flange ordered simply as “F11” may not match the design rating. Therefore, always order flanges as “ASTM A182 F11 Class 2” (or the class your piping specification requires).
A182 F11 Flange Dimensions – ASME B16.5 Class 150 & 300
| NPS | Class 150 – OD / bolt circle (in) / bolts | Class 300 – OD / bolt circle (in) / bolts |
| ½” | 3.50 / 2.38 / 4 × ½” | 3.75 / 2.62 / 4 × ½” |
| ¾” | 3.88 / 2.75 / 4 × ½” | 4.62 / 3.25 / 4 × ⅝” |
| 1″ | 4.25 / 3.12 / 4 × ½” | 4.88 / 3.50 / 4 × ⅝” |
| 1½” | 5.00 / 3.88 / 4 × ½” | 6.12 / 4.50 / 4 × ¾” |
| 2″ | 6.00 / 4.75 / 4 × ⅝” | 6.50 / 5.00 / 8 × ⅝” |
| 3″ | 7.50 / 6.00 / 4 × ⅝” | 8.25 / 6.62 / 8 × ¾” |
| 4″ | 9.00 / 7.50 / 8 × ⅝” | 10.00 / 7.88 / 8 × ¾” |
| 6″ | 11.00 / 9.50 / 8 × ¾” | 12.50 / 10.62 / 12 × ¾” |
| 8″ | 13.50 / 11.75 / 8 × ¾” | 15.00 / 13.00 / 12 × ⅞” |
| 10″ | 16.00 / 14.25 / 12 × ⅞” | 17.50 / 15.25 / 16 × 1″ |
| 12″ | 19.00 / 17.00 / 12 × ⅞” | 20.50 / 17.75 / 16 × 1⅛” |
Dimensions are in inches to ASME B16.5, and bolts are shown as number × diameter. Flange thickness and hub dimensions depend on the flange type, so they are taken from the B16.5 table for each type. In addition, Classes 600 to 2500 and sizes above NPS 12 are supplied to the same standard.
A182 F11 Flange Mechanical Properties
| Property | F11 Class 1 | F11 Class 2 | F11 Class 3 |
| Tensile strength, min | 415 MPa (60 ksi) | 485 MPa (70 ksi) | 515 MPa (75 ksi) |
| Yield strength, min | 205 MPa (30 ksi) | 275 MPa (40 ksi) | 310 MPa (45 ksi) |
| Elongation / RA, min | 20% / 45% | 20% / 30% | 20% / 30% |
| Hardness (HBW) | 121 – 174 | 143 – 207 | 156 – 207 |
Because Class 2 is the class used in the B16.5 rating tables, it is the normal choice for flanges. However, A182 has no impact-test requirement for F11; therefore, toughness testing is added only when the order asks for it.
ASTM A182 F11 Flanges Specifications
| Item | Details |
| Specification | ASTM A182 / ASME SA182, Grade F11 Class 1, 2 or 3 |
| Dimensions | ASME B16.5, B16.47 Series A / B; also MSS SP-44 and drawing |
| Size | NPS ½ to 24 (B16.5), then NPS 26 to 60 (B16.47) |
| Pressure class | 150, 300, 600, 900, 1500, 2500 |
| Facing | RF, FF, RTJ |
| Heat treatment | Annealed, or normalised and tempered at 620 °C (1150 °F) min |
| Testing | Chemistry, tensile and hardness; in addition, UT, PMI and third-party inspection on request |
| Certificate | EN 10204 3.1; also 3.2 on request |
A182 F11 Flange Chemical Composition
| Element (%) | F11 Class 1 | F11 Class 2 & 3 |
| 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 |
| Sulphur (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 |
F11 has two chemistries, so Class 2 and 3 flanges allow more carbon and manganese than Class 1. In addition, the 0.50–1.00% silicon improves oxidation resistance at temperature.
A182 F11 Flanges – Matching Pipe, Fittings & Bolting
| Component | Matching grade |
| Pipe | ASTM A335 P11 |
| Buttweld fittings | ASTM A234 WP11 |
| Forged fittings | ASTM A182 F11 |
| Heavy forgings | ASTM A336 F11 |
| Plate | ASME SA387 Grade 11 |
| Stud bolts / nuts | A193 B7 with A194 2H; also B16 for higher temperatures |
Because P11 lines run hot, bolting is chosen for the design temperature. For example, B7 / 2H is common up to about 450 °C, while A193 B16 studs with Grade 4 or 7 nuts are used above that. In addition, F11 flanges need preheat and post-weld heat treatment when welded to P11 pipe.
Applications of ASTM A182 F11 Flanges
| Industry | Typical A182 F11 flange use |
| Power generation | Main steam, hot reheat and boiler piping, as well as turbine connections |
| Refining | Furnace and high-temperature process lines, while temperatures stay below about 565 °C |
| Petrochemical | Cracker and reformer piping in Cr-Mo service |
| Boilers & HRSG | Header and drum connections |
F11 is generally used up to about 565 °C. However, it is a low-alloy steel, so wet corrosive or seawater service needs stainless, duplex or nickel alloy flanges instead.
A182 F11 Flanges Supplier – ASC LLP, Mumbai
ASC LLP supplies ASTM A182 F11 flanges forged by approved mills, so every flange is traceable to its heat number and certificate. In addition, we supply the matching P11 pipe, WP11 and F11 fittings and stud bolts, so a complete Cr-Mo line can ship together.
For other Cr-Mo grades, see our F5, F9, F22 and F91 flanges.
Frequently Asked Questions – ASTM A182 F11 Flanges
What are ASTM A182 F11 flanges?
They are forged 1¼Cr-½Mo alloy steel flanges to ASTM A182 Grade F11, made to ASME B16.5 or B16.47. They are used on P11 steam and high-temperature piping.
Which F11 class is used for flanges?
F11 Class 2 is normally used, because it is listed in ASME B16.5 Material Group 1.9. Therefore, always state the class on the order.
What are the mechanical properties of F11 Class 2 flanges?
F11 Class 2 has 485 MPa (70 ksi) minimum tensile and 275 MPa (40 ksi) minimum yield strength. In addition, it needs 20% elongation, 30% reduction of area and 143–207 HBW hardness.
What pipe is used with A182 F11 flanges?
A182 F11 flanges are normally welded to ASTM A335 P11 seamless pipe, together with A234 WP11 buttweld fittings.
What bolts are used with F11 flanges?
A193 B7 studs with A194 2H nuts are common up to about 450 °C. However, A193 B16 studs are used at higher temperatures.
What is the maximum temperature for F11 flanges?
F11 is generally used up to about 565 °C (1050 °F). Above that, F22 or F91 flanges are used instead.
Are F11 flanges corrosion resistant?
No. F11 resists oxidation at high temperature, but it is not stainless steel, so it is not used for wet corrosive or seawater service.
Global Supply
ASC LLP supplies ASTM A182 F11 flanges from Mumbai to customers in India, the Middle East, Europe, Africa, the Americas and South-East Asia. To get a prompt quotation, simply send your enquiry with flange type, size, pressure class, facing, schedule (bore), F11 class and quantity.
Countries We Export To
UNITED STATES, EUROPE, UK, UAE, SAUDI ARABIA, OMAN, KUWAIT, JORDAN, QATAR, INDONESIA, MALAYSIA, BRAZIL, SPAIN, ITALY, FRANCE, GERMANY, BAHRAIN, SRI LANKA, AZERBAIJAN, AUSTRALIA, AUSTRIA, PHILIPPINES, TURKEY, RUSSIA, IRAN, IRAQ, CANADA, KOREA, JAPAN, YEMEN, FINLAND, ZIMBABWE, HUNGARY, PORTUGAL, VIETNAM, MOROCCO, THAILAND, SOUTH AFRICA, MEXICO, SINGAPORE, GREECE, KUWAIT, POLAND, NEW ZEALAND, SWEDEN, SWITZERLAND, BELGIUM, BHUTAN, BANGLADESH, TAIWAN, ROMANIA, CAMBODIA, KAZAKHSTAN, AFGHANISTAN.
