Zeron Fastners
Duplex and Super Duplex UNS S31803 Lap Joint Flanges
Duplex and Super Duplex UNS S31803 Lap Joint Flanges (LJF) are two-component assemblies consisting of a hubbed stub end (butt-welded to the pipe) and a loose backing flange (the Lap Joint Flange itself). This design allows the flange to be rotated for easy alignment of bolt holes, simplifying installation and disassembly. Manufactured from Duplex Stainless Steel (Alloy 2205 / UNS S31803), these flanges are often used where periodic dismantling is required or in systems using expensive or exotic pipe material, as only the stub end needs to be made of the expensive Duplex alloy. They are highly valued in applications requiring corrosion resistance and ease of maintenance, such as high-purity systems and large chemical storage tanks.
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Duplex and Super Duplex UNS S31803 Lap Joint Flanges Chemical Composition
| Element | Content (%) |
|---|---|
| Carbon (C) | 0.030 max |
| Manganese (Mn) | 2.00 max |
| Silicon (Si) | 1.00 max |
| Phosphorus (P) | 0.030 max |
| Sulfur (S) | 0.020 max |
| Chromium (Cr) | 21.0 – 23.0 |
| Nickel (Ni) | 4.5 – 6.5 |
| Molybdenum (Mo) | 2.5 – 3.5 |
| Nitrogen (N) | 0.08 – 0.20 |
Duplex and Super Duplex UNS S31803 Lap Joint Flanges Mechanical Properties
| Property | Value |
|---|---|
| Tensile Strength (min) | 620 MPa (90 ksi) |
| Yield Strength (0.2% Offset min) | 450 MPa (65 ksi) |
| Elongation in 4D (min) | 25% |
| Hardness (Brinell max) | 290 HB |