The ASTM A182 F304 weld neck flange is high-pressure pipeline connectors widely applied in industries such as petroleum, chemical, power, and food. Forged from austenitic stainless steel 304 (UNS S30400), these flanges minimize carbide precipitation during welding, reducing the risk of intergranular corrosion. They offer excellent acid corrosion resistance (resistant to nitric acid, organic acids, etc.), enhance structural strength, and mitigate welding stress concentration, thus ensuring superior corrosion resistance, high-temperature strength, and welding performance.This article provides a detailed introduction to the ASTM A182 F304 weld neck flange.
What Is a Weld Neck Flange?
A weld neck flange generally refers to a flange with a neck and a circular pipe transition, which is connected to the pipeline through weld neck flanges. Weld neck flanges are characterized by non-deformability, excellent sealing performance, and corresponding rigidity and elasticity. The large distance between the weld joint and the mating surface ensures that the mating surface is not deformed by welding heat, making them widely used in pipeline welding applications.
Specification of ASME B16.5 Weld Neck Flange：
| Shape Type | Regular and Long Neck |
| Sealing Face | RF, FF, FTJ |
| Size Range | 1/2″ – 48″/ DN15 – DN1200 |
| Pressure Rating | Class 150, 300, 600, 900, 1500, 2500lb |
| Standard | ASME B16.5, ASME B16.47 Series A/B |
| Carbon Steel | ASTM A105 / A105N |
| Low Temp Carbon Steel | ASTM A350 LF2/LF3 |
| Pipeline Steel | ASTM A694 F42 / 46 / 56 / 60 / 65 |
| Alloy Steel | ASTM A182 F11 / 12 / 5 / 9 / 91 / 92 |
| Stainless Steel | ASTM A182 F304/304L/304H, 316/316L, 310S, 317,347,904L |
| Duplex Stainless Steel | ASTM A182 F51, F53, F44 |
ASTM A182 F304 Flange Chemical Composition：
| CHEMICAL | LIMITS | C | Mn | P | S | Si | Ni | Cr | Mo | N |
| ASTM A182 F304 | MIN | 8.0 | 18.0 | |||||||
| MAX | 0.08 | 2.00 | 0.045 | 0.030 | 1.00 | 11.0 | 20.0 | 0.10 |
ASTM A182 F304 Flange Mechanical Property：
| MATERIAL | T.S (MPA) | Y.S (MPA) | EL % | R/A % |
| ASTM A182 F304 | 515 min | 205 min | 30 min | 50 min |
Dimension of Weld Neck Flange:
ZIZI specializes in the production and supply of various types of stainless steel weld neck flanges, which cover pressure values including 150#, 300#, 400#, 600#, 900#, 1500# and so on.
| Nominal Pipe Size | A | B | C | D | E | F | G | H | I | J | Weight | |
| inch | mm | mm | mm | mm | mm | mm | mm | mm | Holes | mm | mm | kg / piece |
| 1/2 | 21.30 | 88.90 | 15.70 | 11.20 | 47.80 | 21.30 | 30.20 | 35.00 | 4 | 15.70 | 60.45 | 0.48 |
| 3/4 | 26.70 | 98.60 | 20.80 | 12.70 | 52.30 | 26.70 | 38.10 | 42.90 | 4 | 15.70 | 69.85 | 0.71 |
| 1 | 33.40 | 108.0 | 26.70 | 14.20 | 55.60 | 33.50 | 49.30 | 50.80 | 4 | 15.70 | 79.25 | 1.01 |
| 11/4 | 42.20 | 117.3 | 35.10 | 15.70 | 57.15 | 42.20 | 58.70 | 63.50 | 4 | 15.70 | 88.90 | 1.33 |
| 11/2 | 48.30 | 127.0 | 40.90 | 17.50 | 62.00 | 48.30 | 65.00 | 73.15 | 4 | 15.70 | 98.60 | 1.72 |
| 2 | 60.30 | 152.4 | 52.60 | 19.10 | 63.50 | 60.45 | 77.70 | 91.90 | 4 | 19.10 | 120.7 | 2.58 |
| 21/2 | 73.00 | 177.8 | 62.70 | 22.40 | 69.85 | 73. 15 | 90.4 | 104.6 | 4 | 19.10 | 139.7 | 4.11 |
| 3 | 88.90 | 190.5 | 78.00 | 23.90 | 69.85 | 88.90 | 108.0 | 127.0 | 4 | 19.10 | 152.4 | 4.92 |
| 31/2 | 101.6 | 215.9 | 90.20 | 23.90 | 71.40 | 101.6 | 122.2 | 139.7 | 8 | 19.10 | 177.8 | 6.08 |
| 4 | 114.3 | 228.6 | 102.40 | 23.90 | 76.20 | 114.3 | 134.9 | 157.2 | 8 | 19.10 | 190.5 | 6.84 |
| 5 | 141.3 | 254.0 | 128.3 | 23.90 | 88.90 | 141.2 | 163.6 | 185.7 | 8 | 22.40 | 215.9 | 8.56 |
| 6 | 168.3 | 279.4 | 154.2 | 25.40 | 88.90 | 168.4 | 192.0 | 215.9 | 8 | 22.40 | 241.3 | 10.6 |
| 8 | 219.1 | 342.9 | 202.7 | 28.40 | 101.6 | 219.2 | 246.1 | 269.7 | 8 | 22.40 | 298.5 | 17.6 |
| 10 | 273.0 | 406.4 | 254.5 | 30.20 | 101.6 | 273.0 | 304.8 | 323.8 | 12 | 25.40 | 362.0 | 24.0 |
| 12 | 323.8 | 482.6 | 304.8 | 31.75 | 114.3 | 323.8 | 365.3 | 381.0 | 12 | 25.40 | 431.8 | 36.5 |
| 14 | 355.6 | 533.4 | To be specified by the Purchaser | 35.10 | 127.0 | 355.6 | 400.1 | 412.7 | 12 | 28.40 | 476.3 | 48.4 |
| 16 | 406.4 | 596.9 | 36.60 | 127.0 | 406.4 | 475.2 | 469.9 | 16 | 28.40 | 539.8 | 60.6 | |
| 18 | 457.2 | 635.0 | 39.60 | 139.7 | 457.2 | 505.0 | 533.4 | 16 | 31.75 | 577.9 | 68.3 | |
| 20 | 508.0 | 698.5 | 42.90 | 144.5 | 508.0 | 558.8 | 584.2 | 20 | 31.75 | 635.0 | 84.5 | |
| 24 | 609.6 | 812.8 | 47.80 | 152.4 | 609.6 | 663.4 | 692.1 | 20 | 35.10 | 749.3 | 115 | |
Solution Annealing:
Solid solution treatment can significantly enhance corrosion resistance, optimize mechanical properties and stabilize the organizational structure.
(I) Heating Stage
Place the ASTM A182 F304 weld neck flanges into a heat treatment furnace and slowly raise the temperature to 1050–1100°C, which is the optimal solution annealing temperature range for F304 stainless steel. At this temperature, chromium carbides (Cr₂₃C₆) can fully dissolve into the austenitic matrix without causing excessive growth of austenite grains that would degrade material properties. The heating rate must be strictly controlled at 5–10°C/min to prevent internal thermal stress in the flanges due to rapid heating, which may cause deformation or cracking.
(II) Holding Stage
After the flanges reach the target temperature, they shall be held at 1050–1100°C for a period determined by the flange size and thickness. Typically, the holding time is 30–60 minutes per 25mm thickness to ensure complete dissolution of chromium carbides and uniform diffusion of alloying elements (e.g., Cr, Ni) in the austenite. Metallographic microscopy inspection of post-holding samples reveals complete disappearance of chromium carbides, with a homogeneous austenitic structure conforming to ASTM A923 standards.
(III) Cooling Stage
Upon completion of the holding period, the flanges shall be rapidly removed from the furnace and cooled using water cooling (WC) or air cooling (AC). The cooling rate must reach ≥10°C/s to suppress reprecipitation of dissolved carbides at grain boundaries, thereby stabilizing the homogeneous austenitic structure at room temperature. Insufficient cooling rate will lead to re-precipitation of chromium carbides along grain boundaries, increasing intergranular corrosion susceptibility (in compliance with ASTM A262 intergranular corrosion test requirements) and causing solution treatment failure.
Packaging:
Protective Caps or Rings:
Plastic or wooden protective caps/rings are typically used on the sealing surface and bevel ends of the flange. These protective devices effectively prevent scratches, dents, or deformation during handling and transportation.
Stretch Film or Bubble Wrap:
Individual flanges may be wrapped with stretch film or bubble wrap before being packed into crates to provide extra physical protection.
Fully Enclosed Wooden Crates:
Used for export, long-distance transportation, or environments with high moisture and dust protection requirements. Wooden crates offer the highest level of protection and can withstand significant external pressure and impact.
Wooden Pallet with Wooden Frame or Cover Boards:
For flanges with regular shapes or in larger quantities, they can be stacked on wooden pallets, secured with a wooden frame or cover boards, and strapped with packing bands. This method is forklift-friendly and suitable for bulk handling.
Areas of Application：
Petroleum And Natural Gas Industry: Refinery piping systems, offshore platforms.
Chemical And Petrochemical Industry: Reaction vessels, distillation columns, acid transport pipelines.
Food And Pharmaceutical Industry: Dairy processing equipment, beer fermentation tanks.
Construction And Infrastructure: High-rise building fire protection systems, urban heating pipelines.
Conclusion
The ASTM A182 F304 weld neck flange is a reliable stainless steel flange designed for piping systems, offering good corrosion resistance and strength. It is commonly used in chemical, water, and industrial applications, providing long-lasting performance and easy installation.
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