ASTM A182 F51 UNS S31803 Duplex 2205 Blind RF Flange for Oil and Gas Piping
ASTM A182 F51 Blind RF Flange is a forged duplex stainless steel flange manufactured from UNS S31803 / Duplex 2205 material.
The blind flange is designed to close the end of a piping system, pressure vessel nozzle or equipment connection. Its raised-face configuration provides a defined gasket seating surface for bolted flange connections.
ASTM A182 covers forged or rolled alloy and stainless steel pipe flanges, forged fittings, valves and similar pressure-system components. The specification includes ferritic-austenitic duplex stainless steel grades such as F51.
Duplex 2205 combines an austenitic-ferritic microstructure with relatively high mechanical strength and resistance to localized corrosion and stress-corrosion cracking compared with many conventional austenitic stainless steels.
Product Specifications
| Item |
Specification |
| Product |
Blind RF Flange |
| Standard |
ASTM A182 / A182M |
| Grade |
F51 |
| UNS |
S31803 |
| Material |
Duplex Stainless Steel |
| Common Grade Name |
Duplex 2205 |
| Flange Type |
Blind Flange |
| Facing |
Raised Face (RF) |
| Manufacturing |
Forged |
| Dimensional Standard |
ASME B16.5 / ASME B16.47 where applicable |
| Pressure Class |
150#, 300#, 600#, 900#, 1500#, 2500# |
| Size |
NPS 1/2–24 or customized |
| Surface |
Machined / Smooth / Customer specified |
| Heat Treatment |
Solution Annealed |
| Marking |
Standard, Grade, Size, Class and Heat No. |
| Inspection |
Chemical, Mechanical, Dimensional and NDT as specified |
ASTM A182 F51 / UNS S31803
ASTM A182 F51 corresponds to the duplex stainless steel grade commonly identified as UNS S31803 / Duplex 2205. Outokumpu's forging-grade reference lists F51 with UNS S31803 and identifies the material as duplex stainless steel.
Typical alloying elements include:
- Chromium
- Nickel
- Molybdenum
- Nitrogen
- Manganese
- Silicon
- Carbon
The duplex microstructure consists of both ferritic and austenitic phases. This structure contributes to the combination of mechanical strength and corrosion performance associated with Duplex 2205.
Typical Chemical Composition
| Element |
Typical / Specification Range |
| C |
≤0.030% |
| Si |
≤1.00% |
| Mn |
≤2.00% |
| P |
≤0.030% |
| S |
≤0.020% |
| Cr |
21.0–23.0% |
| Ni |
4.5–6.5% |
| Mo |
2.5–3.5% |
| N |
0.08–0.20% |
| Fe |
Balance |
For actual deliveries, the applicable ASTM edition and purchase specification should govern the certified chemical composition.
Mechanical Properties
For ASTM A182 F51, mechanical properties should be stated according to the applicable ASTM A182 edition and product condition.
Typical values commonly associated with F51 include:
| Property |
Typical Requirement |
| Tensile Strength |
≥620 MPa |
| Yield Strength |
≥450 MPa |
| Elongation |
≥25% |
| Reduction of Area |
According to applicable specification |
| Hardness |
According to ASTM A182 requirement |
Blind RF Flange Design
The product consists of a solid forged flange body with no central bore.
The main features include:
Blind Face
The blind flange closes the end of a pipe or equipment nozzle without providing a flow passage.
Raised Face
The RF face provides a defined gasket contact area for bolted flange connections.
Bolt Holes
Bolt-hole diameter, quantity and PCD are manufactured according to the applicable dimensional standard and pressure class.
Flange Thickness
Thickness is determined according to:
- NPS
- Pressure Class
- Applicable dimensional standard
- Design requirements
Outside Diameter
The flange OD depends on the nominal size and pressure class.
Manufacturing Process
Typical manufacturing process:
- Duplex stainless steel raw material inspection
- Heat number identification
- Cutting
- Forging
- Heat treatment
- Solution annealing
- Machining
- RF face machining
- Bolt-hole drilling
- Marking
- Dimensional inspection
- PMI
- NDT when required
- Final inspection
- Packaging
ASTM A182 includes requirements covering heat treatment and mechanical/chemical properties for the ordered grade.
Applications
Oil and Gas
- Pipeline isolation
- Process piping
- Wellhead-associated piping
- Offshore piping systems
- Gas processing systems
Petrochemical
- Process piping
- Chemical transfer systems
- Pressure piping
- Equipment nozzles
Marine and Offshore
- Seawater-related systems
- Offshore process equipment
- Marine piping
Chemical Processing
- Corrosive process piping
- Chemical transfer lines
- Pressure-containing piping components
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