SS 321 Buttweld Fittings are made to ASTM A403 / ASME SA403 WP321 for high-temperature refinery service. Elbows, tees, reducers and caps are dimensioned to ASME B16.9 and bevelled for welding into SS 321 pipe.
Raaj Fittings manufactures SS 321 buttweld fittings in-house at our two plants in India, seamless and welded, from ½" upwards, and exports them to EPC contractors, fabricators and stockists across the Middle East, Europe and the Americas, with full traceability and EN 10204 certificates.
| Material specification | ASTM A403 / ASME SA403 WP321 |
|---|---|
| Construction | Seamless and welded |
| Dimensional standards | ASME B16.9, MSS SP-43; bevelled ends to ASME B16.25 |
| Size range | ½" to 48" NPS; larger sizes to order |
| Wall thickness | SCH 5S, 10S, 40S, 80S and heavier walls to order |
| Certification | EN 10204 3.1 mill test certificate as standard; EN 10204 3.2 on request |
SS 321 is an 18-8 stainless steel stabilised with titanium. The titanium ties up carbon as titanium carbides, so chromium carbides cannot form at the grain boundaries when the steel is held between about 425 °C and 815 °C, the range where ordinary 304 becomes sensitised.
| Element, % | S32100 |
|---|---|
| Carbon (C) | 0.08 max |
| Manganese (Mn) | 2.00 max |
| Phosphorus (P) | 0.045 max |
| Sulphur (S) | 0.030 max |
| Silicon (Si) | 1.00 max |
| Chromium (Cr) | 17.0 – 19.0 |
| Nickel (Ni) | 9.0 – 12.0 |
| Titanium (Ti) | 5 × (C + N) min, 0.70 max |
| Nitrogen (N) | 0.10 max |
| Property | SS 321 |
|---|---|
| Tensile strength, min. | 515 MPa (75 ksi) |
| Yield strength (0.2%), min. | 205 MPa (30 ksi) |
| Elongation in 50 mm, min. | 30% |
| Reduction of area, min. | 50% |
| UNS | Werkstoff Nr. | EN / DIN | Other |
|---|---|---|---|
| S32100 | 1.4541 | X6CrNiTi18-10 | SUS 321 |
SS 321 fittings are hot-formed seamless from pipe or made from plate and welded pipe, then solution annealed so that formed and welded areas regain full corrosion resistance. Welded fittings can be ordered with fully radiographed (WX) or ultrasonically tested (WU) seams.
Every heat is PMI-verified and its chemistry and mechanical properties are confirmed against the material specification before the buttweld fittings are released. Each piece is marked with grade, size, rating and heat number for traceability to its EN 10204 3.1 mill test certificate. EN 10204 3.2 certification and inspection by the buyer's nominated third-party agency are available on request, as are PED 2014/68/EU compliance for European projects and IBR certification for Indian boiler applications.
Both are stabilised 18-8 grades: 321 uses titanium and 347 uses niobium (columbium). 347 is often preferred for welding because niobium is not lost in the arc, and 347 filler is used for both.
321 is chosen for long service between about 425 °C and 815 °C, where 304L would lose strength and 304 would sensitise. For ambient-temperature corrosion service, 304L is normally enough.
Yes. Smaller sizes are normally seamless and larger sizes welded, with weld examination as the specification and your order require. Tell us the size, schedule and any construction requirement.
Every order is supplied with EN 10204 3.1 mill test certificates showing heat chemistry and mechanical properties to ASTM A403 WP321. EN 10204 3.2 certification and inspection by your nominated third-party agency are available on request.