What is the difference between A479 S31803 and A182 F51?
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ASTM A479 S31803 and ASTM A182 F51 both refer to duplex stainless steel UNS S31803, commonly known as 2205 duplex. However, they are not interchangeable and serve different purposes in piping and pressure equipment systems.
This article answers frequently asked questions like:
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Is A479 S31803 the same as A182 F51?
Yes. Both A479 S31803 and A182 F51 are based on the same chemical composition:
UNS S31803 typically contains:
21–23% Chromium
4.5–6.5% Nickel
2.5–3.5% Molybdenum
~0.15–0.20% Nitrogen
This duplex alloy balances austenitic and ferritic microstructures for high strength and excellent corrosion resistance.
A479 S31803 Specification
| Specification | ASTM A479 S31803 | ASTM A182 F51 |
|---|---|---|
| Standard Type | Material specification | Forged fittings/flanges specification |
| Product Form | Bars, rods, and forged raw stock | Forged flanges, valves, and pressure parts |
| Typical Use | Raw materials for machining or fabrication | Final forged components in piping systems |
| UNS Number | S31803 | S31803 |
A479 S31803 Heat Treatment & Mechanical Properties
| Property | A479 S31803 / A182 F51 (typical) |
|---|---|
| Yield Strength | ≥ 450 MPa (65 ksi) |
| Tensile Strength | ≥ 620 MPa (90 ksi) |
| Elongation | ≥ 25% |
| Hardness | ≤ 290 HBW |
Is A479 S31803 the same as A182 F51?
They have the same chemical composition (UNS S31803), but are used for different product forms. A479 is for raw stock, A182 is for forged components.
Can A479 be used instead of A182?
Only if you're machining your own forged parts. For final forged flanges and fittings, A182 F51 is required.
What is the UNS number for A182 F51?
The UNS designation is S31803, same as A479 S31803.
What's the difference between A182 and A479?
A182 covers forgings and pressure-bearing components.
A479 covers bars and rods used in ASME pressure vessels and piping systems.
