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ASTM A182 F91 forged fittings are high-temperature, high-strength alloy steel components used in pressure piping systems, particularly in the power generation, petrochemical, and oil & gas industries.
Alloy Steel ASTM A182 F91 forged fittings are pipe fittings manufactured from a specific grade of alloy steel under the ASTM A182 specification. This specification covers forged or rolled alloy steel forged fittings,flanges and valves and parts intended for high-temperature service.
ASTM A182 F91 is a high-strength alloy steel used primarily for forged fittings, flanges, valves, and parts in high-temperature and high-pressure service—especially in power plants, refineries, and petrochemical industries.
“Standard Specification for Forged or Rolled Alloy and Stainless Steel Pipe Flanges, Forged Fittings, and Valves and Parts for High-Temperature Service”
F91 is part of the ferritic alloy steel family, specifically designed for elevated temperature applications.
Element | Range |
Carbon (C) | 0.08 – 0.12 |
Manganese (Mn) | 0.30 – 0.60 |
Phosphorus (P) | ≤ 0.020 |
Sulfur (S) | ≤ 0.010 |
Silicon (Si) | 0.20 – 0.50 |
Chromium (Cr) | 8.00 – 9.50 |
Molybdenum (Mo) | 0.85 – 1.05 |
Nickel (Ni) | ≤ 0.40 |
Vanadium (V) | 0.18 – 0.25 |
Niobium (Nb) | 0.06 – 0.10 |
Nitrogen (N) | 0.030 – 0.070 |
Property | Value |
Tensile Strength | ≥ 585 MPa (85 ksi) |
Yield Strength | ≥ 415 MPa (60 ksi) |
Elongation | ≥ 20% |
Hardness | ≤ 248 HBW (Brinell) |
Standard/System | Equivalent Grade | Notes |
ASME SA182 | F91 | Identical to ASTM A182, used in ASME Boiler & Pressure Vessel Code (BPVC) |
EN (Europe) | X10CrMoVNb9-1 (1.4903) | EN 10216-2, EN 10222-2; very close match |
DIN | X10CrMoVNb9-1 | German designation |
JIS (Japan) | Similar to STBA28 / STPA28 | Not an exact match, but closest equivalent |
ISO | 10Cr9MoVNbN (unified name) | ISO 2604 alloyed steel designation |
90 Degree Elbow | 45 Degree Elbow |
Equal Tee | Reducing Tee |
Full Coupling | Half Coupling |
Pipe Union | Hex Head Plug |
Pipe Cap | Weldolet |
Specifications: | ASTM A182 / ASME SA182 |
Size: | 1/8” NB to 4” NB (Socketweld & Screwed-Threaded) |
Standards: | ASME 16.11, MSS SP-79, 83, 95, 97, BS 3799 |
Thickness: | 2000 LBS, 3000 LBS, 6000 LBS, 9000 LBS |
Type: | Socket Weld & Threaded Forged Fittings |
The primary ASME standard for forged fittings is:
ASME B16.11 - Forged Fittings, Socket-Welding and Threaded
This standard covers the ratings, dimensions, tolerances, marking, and material requirements for forged fittings that are either:
Socket Weld: Fittings designed to be inserted into a recessed area of a pipe and then welded.
Threaded: Fittings with internal threads designed to screw onto pipes with external threads.
Pressure Classes (Ratings):
End Type | Class Ratings |
Threaded | 2000, 3000, 6000 |
Socket Weld | 3000, 6000, 9000 |
Sizes: Covers a range of nominal pipe sizes (NPS), typically from 1/8 inch to 4 inches.
Types of fittings: Includes various configurations like elbows (45 and 90 degrees), tees (equal and reducing), crosses, couplings (full and half), caps, plugs, bushings, unions, and more.
ASTM A182 F91 Type 1 and Type 2 are both low-alloy chromium-molybdenum steels used in forgings, but Type 2 has stricter chemical composition requirements for molybdenum, vanadium, niobium, tungsten, cobalt, boron, nitrogen, and nickel to enhance both creep resistance and toughness. Type 2 also maintains high allowable stresses.
F91 Type 1:
This is the more standard composition of 9Cr-1Mo-V steel.
The conventional composition per ASTM A182 for many years.
Suitable for high-temperature steam piping and pressure parts.
Still widely used in boilers, headers, piping systems.
F91 Type 2:
This type includes more specific controls on the chemical composition of the 9Cr-1Mo-V steel, particularly for elements like molybdenum, vanadium, niobium, tungsten, cobalt, boron, nitrogen, and nickel. These controls are aimed at improving creep resistance and toughness while maintaining high allowable stresses.
Modified composition with added boron and slightly increased nitrogen.
Designed to improve long-term creep strength in ultra-supercritical (USC) power plants.
Often specified where extended service life at elevated temperatures (580–620°C+) is required.
Manufacturing specifications:
Forging process: emphasizes the importance of forging process to optimize metal structure to improve the mechanical properties and corrosion resistance of materials.
Heat treatment: according to different material types, appropriate heat treatment procedures are specified, such as solution annealing, normalizing, quenching and tempering, etc., to achieve the required microstructure and mechanical properties.
Surface quality: specifies requirements for surface roughness, weld groove preparation, non-metallic inclusion removal, etc.
Socket Weld Fittings
TOLERANCES FOR SW FITTINGS | ||||||||||
Nominal Size | All Fittings | Elbows, | Couplings | Half- | Reducer Inserts | Unions | ||||
Socket | Bore Dia. of | Center to | Laying | Laying | Laying | Shank Dia. | Length | Laying | ||
DN | NPS | B | D |
| E | F | A | SD | SL | E |
6~8 | 1/8~1/4 | +0.4 | +1.5 | ± 1.0 | ± 1.5 | ± 1.0 | +1.5 | ± 0.25 | 0 | ± 1.5 |
10~20 | 3/8~3/4 | +0.4 | +1.5 | ± 1.5 | ± 3.0 | ± 1.5 | +1.5 | ± 0.25 | 0 | ± 3.0 |
25~40 | 1~11/2 | +0.4 | +1.5 | ± 2.0 | ± 4.0 | ± 2.0 | +2.0 | ± 0.25 | 0 | ± 4.0 |
50 | 2 | +0.5 | +1.5 | ± 2.0 | ± 4.0 | ± 2.0 | +2.0 | ± 0.5 | 0 | ± 4.0 |
65~80 | 21/2~3 | +0.5 | +3.0 | ± 2.5 | ± 5.0 | ± 2.5 | +2.5 | ± 0.5 | 0 | ± 5.0 |
100 | 4 | +0.5 | +3.0 | ± 2.5 | ± 5.0 | ± 2.5 | +2.5 | ± 0.7 | 0 | - |
TOLERANCES FOR THRD FITTINGS | ||||
Nominal Size | Elbows,Tees & Crosses | Couplings | Half- couplings | |
Center-to-End | End-to-End | End-to-End | ||
DN | NPS |
| W | W/ 2 |
6~8 | 1/8~1/4 | ± 1.0 | ± 1.0 | ± 1.0 |
10~20 | 3/8~3/4 | ± 1.5 | ± 1.5 | ± 1.5 |
25~50 | 1~2 | ± 2.0 | ± 2.0 | ± 2.0 |
65~100 | 21/2~4 | ± 2.5 | ± 2.5 | ± 2.5 |
Steam pipelines in high-pressure boilers
Headers and superheaters
Heat exchangers and pressure vessels
Refinery and chemical plant piping
Nuclear and thermal power plants
1. High Temperature Strength
2. Superior Mechanical Properties
3. Excellent Oxidation & Corrosion Resistance
4. Dimensional Stability
5. Compatibility with Welding and Fabrication
6. Long Service Life
Power Generation
Steam pipelines, headers, and superheater tubing
Ultra-supercritical boilers and HRSG (Heat Recovery Steam Generator) systems
Oil & Gas Industry
Refinery piping systems
High-temperature hydrocracking and catalytic reforming units
Petrochemical & Chemical Plants
Process piping exposed to corrosive gases and high thermal loads
Heat exchangers and reactor lines
Industrial Boilers
High-pressure, high-temperature feedwater and steam circuits
Marine & Offshore
-Pipe and Tube (EN 10216-5, ASTM A213, ASTM A249, A312, A790,)
-Forged Fitting and Flange (ASTM A182 , ASTM A105,ASTM B564 )
-Butt Weld Fittings (ASTM A234, ASTM A403,ASTM A815)
-Round bar , Billet (ASTM A276, ASTM A479)
- Plate, Sheet, Strip(ASTM A240, EN 10028-7, A480)
-Bolting, Nuts（ASTM A193, A194, A320）
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