ANSI / ASME B16.5 Forged Flange ASTM A182 F9 Alloy Steel Flange Weld Neck / WNRF Flange
ASTM A182 Alloy Steel F9 weld neck flange (WNRF) is a forged 9Cr-1Mo alloy steel flange made to ASME B16.5, with a long tapered hub butt-welded to the pipe and a raised face gasket seat. It is specified for lines that run hot - typically 500 °C to 600 °C in refinery, hydrogen, steam and power service - where carbon steel has already lost its strength and austenitic stainless brings a thermal expansion and stress-corrosion penalty. The forging is heat treated and hardness surveyed, and every piece carries PMI verification so that a 9Cr-1Mo joint is never delivered as an F22 or F5 look-alike.
What it actually solves is the slow failure mode of a hot flange joint: at temperature, the bolt load bleeds away into creep relaxation, the gasket seating stress drops, and the joint starts weeping at the face. A forged weld neck answers that in three ways - the tapered hub transfers the bending moment of the pipe into the flange body instead of into the weld, the 8.0-10.0 % Cr with 0.90-1.10 % Mo chemistry holds tensile and creep strength to a higher temperature than carbon steel, and the raised or ring joint face is machined after heat treatment so flatness and groove geometry are correct in the delivered condition.
ASTM A182 Alloy Steel F9 Flanges Equivalent Grades
| STANDARD |
UNS |
DIN WERKSTOFF NR. |
DIN |
| Alloy F9 |
K90941 |
1.7386 |
X 12 CrMo 9 1 |
ASTM A182 Alloy Steel F9 Flanges Chemical Composition
| Grade |
C |
Mn |
Si |
S |
P |
Cr |
Mo |
| A182 F9 |
0.15 |
0.3-0.6 |
0.5-1 |
0.03 |
0.03 |
8-10 |
0.9-1.1 |
ASME SA182 Alloy Steel F9 Flanges Mechanical Properties
| Grade |
Tensile Strength (Mpa) |
Yield Strength (Mpa) |
Elongation % |
| A182 F9 |
380 |
585 |
20 |
Product scope by flange standard
| Standard |
Scope covered in production |
| ANSI B16.5 / ASME B16.47 |
1/2" to 80" (DN15-DN2000); welding neck, slip on, blind, socket weld, threaded and lap joint designs; 150#, 300#, 600#, 900#, 1500#, 2500#; weld neck wall thickness STD, SCH40, SCH80, SCH160, SCHXXS; coatings black paint, yellow transparent paint, cold and hot dip galvanizing |
| EN 1092-1 |
DN15-DN2000; type 01 plate, type 02 loose, type 05 blind, type 11 welding neck, type 12 slip on, type 13 threaded; PN6, PN10, PN16, PN25, PN40, PN64, PN100; carbon steel C22.8, S235, S235JR, P235GH and stainless 304/304L, 316/316L |
| DIN |
DN15-DN2000; slip on DIN 2573, 2576, 2502, 2503, 2543, 2545; welding neck DIN 2631-2635; blind DIN 2527 PN6-PN40; threaded DIN 2565-2567; loose DIN 2641, 2642, 2656, 2673; carbon steel ST37.2 and stainless 1.4301, 1.4404 |
F9 weld neck flanges are produced to the ASME B16.5 row of the table above; the EN and DIN rows describe the wider flange programme available from the same forging line.
Request a Quotation
To quote an F9 weld neck flange accurately we need four things: size and pressure class (for example 6" CL300), face type (RF or RTJ), the matching pipe schedule so the bevel is prepared correctly, and the quantity with the destination port. Send them through the enquiry form on this page and you will receive a quotation stating unit price on an FOB / CIF basis, MOQ, lead time, packing method and the document package included - typically within one working day.
For repeat or frame orders, quote the previous order or certificate number and the same forging and heat-treatment route will be applied.
Applications
F9 weld neck flanges are normally found at the hot end of a plant - the positions where the line temperature rules out carbon steel and the fluid rules out austenitic stainless:
- Refinery process lines and hydroprocessing / hydrogen service, where hot hydrogen attack resistance is required
- High-temperature steam headers, superheater and reheater piping in power generation
- Catalytic reforming, coking and visbreaking units with thermal cycling duty
- Heat exchangers, boilers and fired heaters on the hot side of the equipment
- Petrochemical and chemical processing equipment handling high-temperature hydrocarbon or gas
- Offshore and onshore oil and gas gathering lines where the design temperature exceeds carbon steel limits
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