ASTM A182 F51/S31803 Duplex Flange
Material Characteristics
The ASTM A182 F51 flanges refer to standard or non-standard flanges manufactured in accordance with ASTM A182 Grade F51, which is designated with UNS number S31803. The A182 Gr. F51 / S31803 material is a typical duplex stainless steel, which contains approximately 50% ferrite and 50% austenite. The combination of the ferritic phase and austenitic phase provides both high strength and excellent corrosion resistance. It also provides improved formability and weldbility not obtained in any one of the usual stainless steels.
Early duplex stainless steels can withstand uniform corrosion and chlorine stress corrosion cracking at moderate strength, but their performance is greatly reduced when used in welding situations. Nitrogen is added to S31803 duplex flanges to improve this situation, which not only improves corrosion resistance, but also welds well. It has high strength, good impact toughness and good overall and local stress corrosion resistance. The S31803 flanges can’t to be used over 315°C, as the material may become brittle when used at moderate temperatures.
Flange Specifications
The duplex F51 flanges can be provided in a variety of flange types such as welding neck, slip on, blind, plate, threaded, socket welding, long weld neck, spectacle blind, spade, spacer, and orifice, etc. It may be manufactured in accordance with a plurality of standard specifications such as ASME B16.5, ASME B16.47, API 6A, ASME B16.48, ASME B16.36, BS 4504, EN 1092-1, NOSOK L-005, and DIN 2633, etc. Tailor-made flanges are also available as long as the client provides an engineered drawing. Typically, ASTM A182 F51 flanges conforming to ASME B16.5 may be furnished in sizes NPS 1/2 to NPS 24 Class 150 through Class 2500, whilst flanges conforming to ASME B16.47 may be provided in sizes NPS 26 to NPS 60 Class 75 to Class 900. EN 1092-1 flanges will be provided in pressure ratings of PN designations from PN 10 to PN 400.
Manufacture & Heat Treatment
The ASTM A182 F51 flanges with hub shall be manufactured by a hot forging process, in which the material shall be forged as close as practicable to the specified shape and size. The F51 duplex flanges without hub shall be manufactured from plate in according to ASTM A240. After hot forging, the duplex F51 flanges shall be cooled to a temperature below 1000°F [538°C] prior to heat treatment. Then the flange shall be solution annealed and quenched. It shall be heated to a temperature higher than 1870°F [1020°C], holding for a period of time, and quenched in cold water or oil rapidly to a temperature below 500°F [260°C].
Chemical Composition Requirements
| Chemical composition for ASTM A182 F51 flange, % | |
|---|---|
| Carbon | 0-0.03 |
| Chromium | 21.00-23.00 |
| Manganese | ≤2.00 |
| Silicon | ≤1.00 |
| Phosphorous | 0-0.03 |
| Sulfur | 0-0.02 |
| Nickel | 4.50-6.50 |
| Nitrogen | 0.08-0.20 |
| Molybdenum | 2.50-3.50 |
| Iron | Balance |
Mechanical Properties
| Tensile Strength,min. | Yield Strength,min. | Elongation,min. | Hardness Brinell, max |
|---|---|---|---|
| Mpa | Mpa | % | HB |
| 620 | 450 | 25 | 290 |
Tests and Inspection
One tension test shall be made for each heat of ASTM A182 F51 flanges. One set of three Charpy V-notch tests shall be performed for each heat of products. When required by the purchaser, detecting of detrimental phase in the duplex stainless steel shall be conducted in accordance with ASTM A923 or ASTM A1084. Non-destructive tests such as ultrasonic test (UT), magnetic particle inspection (MPI), or liquid penetration examination may be performed upon client’s request. There shall be no welding repair and the duplex F51 flanges shall have a workmanlike finish, and the machined surfaces shall have a surface finish not to exceed 250 AA roughness height.
Pressure-Temperature Rating
| Temp. ℃ | Pressure-temperature rating for ASME B16.47 by class, bar | |||||
| 75 | 150 | 300 | 400 | 600 | 900 | |
| -29 to 38 | 10.0 | 20.0 | 51.7 | 68.9 | 103.4 | 155.1 |
| 50 | 9.8 | 19.5 | 51.7 | 68.9 | 103.4 | 155.1 |
| 100 | 8.8 | 17.7 | 50.7 | 67.5 | 101.3 | 152.0 |
| 150 | 7.9 | 15.8 | 45.9 | 61.2 | 91.9 | 137.8 |
| 200 | 6.9 | 13.8 | 42.7 | 56.9 | 85.3 | 128.0 |
| 250 | 6.0 | 12.1 | 40.5 | 53.9 | 80.9 | 121.4 |
| 300 | 5.1 | 10.2 | 38.9 | 51.8 | 77.7 | 116.6 |
| 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 |
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