ASTM A182 Grade F51 Duplex Stainless Steel Flanges
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What is ASTM A182 gr F51 material?
ASTM A182 F51 (UNS S31803) is a duplex stainless steel forging grade containing 22% chromium, 5% nickel, 3% molybdenum, and 0.15% nitrogen. It features a mixed austenitic-ferritic microstructure and is suitable for acidic and chloride-rich environments. It is commonly used for valves, flanges, and pump components in sectors such as the petroleum, chemical, and seawater treatment industries. With an operating temperature range of -50°C to 300°C, a Pitting Resistance Equivalent Number (PREN) of ≥35, and compliance with the NACE MR0175 standard, it is an ideal choice for demanding service conditions.
What is the material equivalent of ASTM A182 F51?
ASTM A182 F51 is a standard duplex stainless steel. Its primary material equivalents are UNS S31803 and the European standard DIN 1.4462 (often written as X2CrNiMoN22-5-3). It is also widely known in the industry by the trade names Duplex 2205 or Alloy 2205.
What is the difference between F51 and F60?
F51 (S31803) represents the original duplex stainless steel standard, while F60 (S32205) is an improved version of S31803. S32205 features higher minimum levels of nitrogen (N) and molybdenum (Mo), resulting in more consistent corrosion resistance (PREN value). Currently, most F51 flanges on the market are "dual certified"-meaning they meet the requirements of both S31803 and S32205-to ensure superior performance.
ASTM A182 F51 Duplex Stainless Steel Flanges Specification
| Item | Specification |
|---|---|
| Product Name | ASTM A182 Grade F51 Duplex Stainless Steel Flanges |
| Material Grade | F51 / UNS S31803 / EN 1.4462 |
| Standard | ASTM A182 / ASME SA182 |
| Flange Type | Weld Neck (WN), Slip On (SO), Blind (BL), Socket Weld (SW), Threaded (TH), Lap Joint (LJ), Plate Flange |
| Size Range | 1/2" – 60" (DN15 – DN1500) |
| Pressure Class | Class 150, 300, 600, 900, 1500, 2500 |
| Pressure Rating | ASME B16.5 / ASME B16.47 |
| Dimensions Standard | ASME B16.5, ASME B16.47 Series A/B |
| Facing Type | Raised Face (RF), Flat Face (FF), Ring Type Joint (RTJ) |
| Forging Process | Open Die Forging / Closed Die Forging |
| Heat Treatment | Solution Annealing + Rapid Cooling |
| Surface Treatment | Machined Finish, Sand Blasting, Pickling & Passivation |
| Thickness | According to ASME B16.5 / Customer Drawing |
| Marking | Material Grade, Size, Pressure Class, Heat Number, Manufacturer Identification |
| Inspection Standard | ASTM A961, ASME B16.5, EN 10204 3.1 |
ASTM A182 F51 SS Flanges Chemical Composition
| Chemical Composition Limits | |||||||||
| Weight% | C | Mn | P | S | Si | Cr | Ni | Mo | N |
| Duplex F51 | 0.03 max | 2.0 max | 0.03 max | 0.02 max | 1 max | 21-23 | 4.5-6.5 | 2.5-3.5 | 0.80-0.20 |
Mechanical Properties Of ASTM A182 F51 Stainless Pipe Flanges
| Alloy | Tensile Strength N/mm² | Proof Strength 0.2% N/mm² | Elongation (%) | Hardness Brinell |
| F51 | 105 | 55 | 35 | 170-255 |
Pressure Rating Table of ASTM A182 F51 Pipe Flanges
| Temp, ℃ | Pressure-temperature rating for ASME B16.5 by class, bar | ||||||
| 150 | 300 | 400 | 600 | 900 | 1500 | 2500 | |
| -29 to 38 | 20.0 | 51.7 | 68.9 | 103.4 | 155.1 | 258.6 | 430.9 |
| 50 | 19.5 | 51.7 | 68.9 | 103.4 | 155.1 | 258.6 | 430.9 |
| 100 | 17.7 | 50.7 | 67.5 | 101.3 | 152.0 | 253.3 | 422.2 |
| 150 | 15.8 | 45.9 | 61.2 | 91.9 | 137.8 | 229.6 | 382.7 |
| 200 | 13.8 | 42.7 | 56.9 | 85.3 | 128.0 | 213.3 | 355.4 |
| 250 | 12.1 | 40.5 | 53.9 | 80.9 | 121.4 | 202.3 | 337.2 |
| 300 | 10.2 | 38.9 | 51.8 | 77.7 | 116.6 | 194.3 | 323.8 |
GNEE provides ASTM A182 F51 Duplex Stainless Steel Flanges in customized sizes, pressure ratings and facing types. Available options include Class 150–2500 pressure ratings, RF/RTJ/FF facing, forged construction and customized machining.
Available Flange Types
| Flange Type | Application |
|---|---|
| Weld Neck Flange (WN) | High-pressure pipelines, offshore and petrochemical systems |
| Slip On Flange (SO) | General industrial piping connections |
| Blind Flange (BL) | Pipeline isolation and pressure testing |
| Socket Weld Flange (SW) | Small diameter high-pressure piping |
| Threaded Flange | Low-temperature and non-welded applications |
| Lap Joint Flange | Systems requiring frequent dismantling |
If you are looking to source or specify this material, tell me:What pressure class or size do you need?Which type of flange (e.g., Weld Neck or Blind) do your drawings require?I can help you narrow down the technical specifications.
Heat Treatment for ASTM A182 F51 Flanges
Solution Annealing: Heating within the 1020°C–1100°C range, followed by water quenching.
Purpose: To ensure a ferrite-to-austenite ratio close to 50:50. Insufficient cooling rates can lead to the precipitation of harmful intermetallic phases (such as the sigma phase), causing a drastic drop in toughness and corrosion resistance.
Why are F51 flanges unsuitable for long-term use at extremely high or low temperatures?
High-temperature limit: Above 300°C, "475°C embrittlement" occurs, resulting in a loss of toughness.
Low-temperature limit: Although performance is superior to standard ferritic steels, toughness begins to decline below -50°C (use in cryogenic applications is generally not recommended unless specially reinforced).
Applications of ASTM A182 F51 flanges
Oil and Gas Industry: Offshore platforms, subsea production systems, and oil and gas transmission pipelines.
Chemical Processing: Pressure vessels, pumps, and valves used in the production of chlorides, sulfuric acid, and organic acids.
Desalination: F51 is a highly cost-effective choice for environments involving high-concentration brine.
Pulp and Paper: Bleaching and chemical extraction equipment.
GNEE Stainless Steel is committed to providing global customers in demanding sectors-such as oil and gas, chemicals, marine, and energy-with a stable supply of materials and comprehensive documentation ensuring full quality traceability (including EN 10204 3.1 material test certificates).
Quality Control
ASTM A182 F51 duplex stainless steel flanges undergo rigorous quality testing, including PMI (Positive Material Identification) verification, chemical composition analysis, tensile testing, hardness testing, dimensional inspection, and surface examination. Each flange is supplied with a Material Test Certificate (MTC) compliant with EN 10204 3.1, recording the heat number; inspection reports from third-party agencies such as SGS, BV, or TUV are also available upon customer request.
Packaging
ASTM A182 F51 duplex stainless steel flanges are packaged in strict accordance with international export standards, utilizing anti-corrosion wrapping, plastic protective caps, waterproof film, and sturdy plywood cases or wooden pallets. Each flange is individually marked with size, pressure rating, material grade, and heat number, and is protected against surface damage, moisture-induced corrosion, or deformation during long-distance ocean transport.
