Metinox Overseas supplies SS 321 pipe fittings for process lines that run hot for long periods, such as heater outlets, steam headers and hydroprocessing circuits. Grade 321 is an austenitic stainless steel stabilised with titanium. The titanium combines with carbon first, which keeps chromium carbides from forming at the grain boundaries when the fitting is welded or held between 425 and 815°C, and that is why welded joints keep their corrosion resistance in service. We supply ASTM A403 WP321 and WP321H stainless steel buttweld fittings (UNS S32100 / S32109, DIN 1.4541 / 1.4878), including long and short radius elbows, equal and reducing tees, concentric and eccentric reducers and end caps to ASME B16.9. Forged socket weld and threaded fittings are available to ASTM A182 F321. They sit within our wider pipe fittings range.
Request a QuotationTable of Contents
- SS 321 & 321H Pipe Fittings Specifications
- Chemical Composition of SS 321 & 321H Pipe Fittings
- Mechanical Properties of SS 321 & SS 321H Pipe Fittings
- Equivalent Material Grades of SS 321 Fittings & SS 321H Pipe Fittings
- Physical Properties of SS 321/321H Pipe Fittings
- SS 321 and 321H Pipe Fittings Weight Chart (kg)
- ANSI B16.9 SS 321 Butt Weld Fittings Dimensions (mm)
- Dimensional Tolerances for SS 321 and 321H Pipe Fittings
- Types and Forms of Stainless Steel 321 and 321H Buttweld Fittings
- Where SS 321 and 321H Pipe Fittings Are Used
- Packing, Marking and Delivery of SS 321 Fittings
- Get a Quote for 321 Stainless Steel Pipe Fittings
- Related Products for SS 321 Piping Systems
- SS 321 / 321H Pipe Fittings FAQs
SS 321 & 321H Pipe Fittings Specifications
| Parameter | Details |
|---|---|
| Buttweld standard | ASTM A403 / ASME SA403 WP321, WP321H |
| Forged standard | ASTM A182 / ASME SA182 F321, F321H |
| Types | Seamless, welded, fabricated |
| Dimensional standards | ASME B16.9, ASME B16.28, MSS-SP-43, MSS SP-75 |
| Buttweld fitting size | ½" to 48" NB |
| Forged fitting size | ¼" to 4" |
| Bending Radius | 1D, 2D, 3D, 5D, 6D, 8D, 10D or Custom |
| Forms Available | Elbow, Tee, Reducer, Cap, Stub End, Bend, Cross, Nipple, Coupling |
| Wall thickness | Sch 5S, 10S, 40S, 80S, 160, XXS per ASME B36.19M / B36.10M |
| End finish | Bevelled to ASME B16.25, plain end |
| Heat treatment | Stabilizing Anneal at 870–900°C (321) | Solution Anneal 1040–1121°C (321H) |
Chemical Composition of SS 321 & 321H Pipe Fittings
| Grade | C | Mn | Si | P | S | Cr | Ni | N | Ti |
|---|---|---|---|---|---|---|---|---|---|
| WP321 | 0.08 max | 2.00 max | 1.00 max | 0.045 max | 0.030 max | 17.0 to 19.0 | 9.0 to 12.0 | 0.10 max | 5 × (C+N) min, 0.70 max |
| WP321H | 0.04 to 0.10 | 2.00 max | 1.00 max | 0.045 max | 0.030 max | 17.0 to 19.0 | 9.0 to 12.0 | 0.10 max | 4 × (C+N) min, 0.70 max |
Mechanical Properties of SS 321 & SS 321H Pipe Fittings
| Grade | Tensile strength, min | Yield strength 0.2%, min | Elongation, min | Hardness |
|---|---|---|---|---|
| SS 321 | 515 MPa (75 ksi) | 205 MPa (30 ksi) | 28% longitudinal (A403); 30% (A182) | 95 HRB |
| SS 321H | 515 MPa (75 ksi) | 205 MPa (30 ksi) | As above | 95 HRB |
Equivalent Material Grades of SS 321 Fittings & SS 321H Pipe Fittings
| Grade | UNS | Werkstoff Nr. | EN | JIS | BS (old) |
|---|---|---|---|---|---|
| SS 321 | S32100 | 1.4541 | X6CrNiTi18-10 | SUS 321 | 321S31 |
| SS 321H | S32109 | 1.4878 | X8CrNiTi18-10 | SUS 321H | 321S51 |
Physical Properties of SS 321/321H Pipe Fittings
| Property | Metric | Imperial |
|---|---|---|
| Density | 8.0 g/cm³ | 0.289 lb/in³ |
| Melting range | 1400 to 1425 °C | 2550 to 2600 °F |
| Modulus of elasticity | 193 GPa | 28 × 10⁶ psi |
| Thermal conductivity (100 °C) | 16.1 W/m·K | 9.3 BTU/hr·ft·°F |
| Mean thermal expansion (0 to 100 °C) | 16.6 µm/m·°C | 9.2 µin/in·°F |
| Specific heat (0 to 100 °C) | 500 J/kg·K | 0.12 BTU/lb·°F |
| Electrical resistivity | 720 nΩ·m | - |
SS 321 and 321H Pipe Fittings Weight Chart (kg)
Approximate weights per piece for ASME B16.9 long radius elbows and equal tees. Actual weights vary with manufacturing tolerance and the wall thickness supplied.
| DN (NPS) | Sch 10S 90° LR elbow | Sch 10S 45° LR elbow | Sch 10S equal tee | Sch 40S 90° LR elbow | Sch 40S equal tee | Sch 80S 90° LR elbow | Sch 80S equal tee |
|---|---|---|---|---|---|---|---|
| 15 (½") | 0.06 | 0.03 | 0.09 | 0.08 | 0.10 | 0.10 | 0.14 |
| 25 (1") | 0.14 | 0.08 | 0.28 | 0.15 | 0.29 | 0.22 | 0.38 |
| 50 (2") | 0.50 | 0.25 | 0.85 | 0.70 | 1.28 | 0.91 | 1.59 |
| 80 (3") | 1.25 | 0.63 | 1.77 | 2.20 | 3.31 | 2.97 | 4.45 |
| 100 (4") | 2.10 | 1.08 | 3.46 | 4.47 | 5.27 | 6.18 | 7.71 |
| 150 (6") | 5.45 | 2.72 | 8.07 | 10.89 | 10.99 | 16.32 | 13.61 |
| 200 (8") | 10.20 | 5.33 | 15.65 | 21.54 | 20.91 | 33.11 | 28.12 |
| 300 (12") | 25.80 | 13.62 | 39.46 | 59.42 | 62.14 | 79.38 | 83.91 |
ANSI B16.9 SS 321 Butt Weld Fittings Dimensions (mm)
| NPS | DN | OD mm (in) | 90° LR elbow A | 45° LR elbow B | 90° SR elbow | Tee C/M | Reducer H | Cap E |
|---|---|---|---|---|---|---|---|---|
| 1/2 | 15 | 21.3 (0.840) | 38 | 16 | - | 25 | - | 25 |
| 3/4 | 20 | 26.7 (1.050) | 38 | 19 | - | 29 | 38 | 25 |
| 1 | 25 | 33.4 (1.315) | 38 | 22 | 25 | 38 | 51 | 38 |
| 1 1/2 | 40 | 48.3 (1.900) | 57 | 29 | 38 | 57 | 64 | 38 |
| 2 | 50 | 60.3 (2.375) | 76 | 35 | 51 | 64 | 76 | 38 |
| 3 | 80 | 88.9 (3.500) | 114 | 51 | 76 | 86 | 89 | 51 |
| 4 | 100 | 114.3 (4.500) | 152 | 64 | 102 | 105 | 102 | 64 |
| 6 | 150 | 168.3 (6.625) | 229 | 95 | 152 | 143 | 140 | 89 |
| 8 | 200 | 219.1 (8.625) | 305 | 127 | 203 | 178 | 152 | 102 |
| 10 | 250 | 273.0 (10.750) | 381 | 159 | 254 | 216 | 178 | 127 |
| 12 | 300 | 323.8 (12.750) | 457 | 190 | 305 | 254 | 203 | 152 |
Dimensional Tolerances for SS 321 and 321H Pipe Fittings
| DN / NPS | OD at bevel end | Wall thickness | Elbow centre to end | Tee centre to end | Reducer overall length | 180° return |
|---|---|---|---|---|---|---|
| 15 to 65 / ½" to 2½" | +1.6 / −0.8 mm | −12.5% | ±1.6 mm | ±1.6 mm | ±1.6 mm | ±6.4 mm |
| 80 to 100 / 3" to 4" | ±1.6 mm | −12.5% | ±1.6 mm | ±1.6 mm | ±1.6 mm | ±6.4 mm |
| 125 to 200 / 5" to 8" | +2.4 / −1.6 mm | −12.5% | ±2.4 mm | ±2.4 mm | ±2.4 mm | ±9.6 mm |
| 250 to 450 / 10" to 18" | +4.0 / −3.2 mm | −12.5% | ±2.4 mm | ±2.4 mm | ±2.4 mm | ±9.6 mm |
| 500 to 600 / 20" to 24" | +6.4 / −4.8 mm | −12.5% | ±3.2 mm | ±3.2 mm | ±4.8 mm | ±9.6 mm |
Types and Forms of Stainless Steel 321 and 321H Buttweld Fittings
Not sure which fitting fits your application? Share your size, pressure class and quantity, and our team will recommend the right type with a quick quote. Get a Free Quote
Where SS 321 and 321H Pipe Fittings Are Used
- Refining and petrochemicals: hydrotreater and hydrocracker effluent lines, fired heater coils
- Power and water: steam lines, boiler and HRSG components
- Gas processing and LNG: hot regeneration gas lines
- Fertilizer: high-temperature process lines
- Exhaust and flue systems: turbine and heater exhausts, expansion joints
- Chemical processing: where welded joints can't be solution annealed after fabrication
Packing, Marking and Delivery of SS 321 Fittings
Lead time confirmed at quotation.
- Bevel ends are capped.
- Small fittings are bagged by size.
- Larger items ship in seaworthy wooden cases.
- Fittings are kept clear of carbon steel contact.
- Every case is marked with grade, heat number and size.
At coastal sites, store fittings covered and off the ground, away from chloride spray and sand.
Get a Quote for 321 Stainless Steel Pipe Fittings
Send your line list or material take off with grade, size, schedule, quantity, certification level and destination port. Attach your project material specification if it adds requirements, such as sour service hardness limits or extra testing. A complete enquiry gets a complete quotation on the first reply.
Request a QuotationSS 321 / 321H Pipe Fittings FAQs
321H has a controlled carbon range of 0.04 to 0.10 percent for better creep strength in sustained service above about 540°C. 321 is used where the main concern is sensitisation during welding or heat exposure.
Yes, in most services. Titanium stabilisation limits chromium carbide formation in the heat-affected zone, which is the main reason 321 is chosen for welded hot lines.
ISO 15156-3 accepts 321 in the solution-annealed condition with hardness of 22 HRC maximum, within environmental limits. It is mainly a high-temperature grade, so confirm suitability with your materials engineer.
Buttweld fittings are made to ASTM A403 WP321 with dimensions to ASME B16.9. Forged socket weld and threaded fittings are made to ASTM A182 F321 with dimensions to ASME B16.11.
Send grade, standard, fitting type, size, schedule, quantity, end finish, certification, inspection requirements, destination port and required date.
321 resists scaling in continuous service up to about 870°C and is most often specified for 425 to 815°C, where its titanium stabilisation prevents sensitisation. Above about 540°C under sustained load, specify 321H for creep strength.
Yes, when the heat meets both chemistries (carbon 0.04 to 0.08%) and the 321H heat-treatment requirement. Ask for dual certification at enquiry so the MTC states both grades.
Enquire Now
Get pricing within 24 hours!
