SS 304 pipe fittings are elbows, tees, reducers, caps and stub ends made from the 18 chromium, 8 nickel austenitic stainless steel and supplied to ASTM A403 for buttweld work. One letter on the mill certificate decides how they behave once welded. Grade WP304 allows carbon up to 0.08%, so a field weld can sensitise the zone beside it and open the way to intergranular attack in service, which is why most piping specifications now call for WP304L or dual certified WP304/304L. Check the grade marking on every fitting before fit-up. Metinox Overseas supplies these fittings within its wider pipe fittings range for process, utility and water lines in the GCC and other export markets.
Table of content
- 304 Stainless Steel Pipe Fittings Specification
- ASTM A403 WP304 Fittings vs 304L Stainless Steel Fittings vs WP304H: Picking the Grade
- Chemical Composition of Stainless Steel 304 Fittings
- Mechanical Strength of 304 Stainless Steel Fittings, Buttweld and Forged
- Physical Properties for 304/304L Buttweld Fittings
- 304 / 304L / 304H Equivalent Grades: UNS, Werkstoff, EN and JIS
- Fitting Types: 304/304L Elbow, 304/304L Tee, 304/304L Reducer and More
- 304/304L Buttweld Fittings Dimensions to ASME B16.9 (½" to 24")
- Wall Thickness Schedules for 304L Seamless Pipe Fittings and Welded Fittings
- Where Stainless Steel 304/304L Pipe Fittings Work in GCC and Export Market Plants
- When SS 304 Fittings Are the Wrong Choice: Chlorides, Heat and Humidity
- Certification and PMI: What a 304L Pipe Fittings Exporter Should Send with the Goods
- Packing 304/304L Buttweld Fittings for Sea Freight and Site Laydown
- Request a Quote for SS 304, 304L and 304H Pipe Fittings
- Related Products for SS 304/304L Piping Systems
- Buyer Questions on SS 304 Pipe Fittings and SS 304L Pipe Fittings
304 Stainless Steel Pipe Fittings Specification
| Parameter | Details |
| Material standard, buttweld | ASTM A403 / ASME SA403, grades WP304, WP304L, WP304H |
| Material standard, forged | ASTM A182 / ASME SA182, grades F304, F304L, F304H |
| UNS numbers | S30400 (304), S30403 (304L), S30409 (304H) |
| Types | Seamless, welded, fabricated |
| Dimension | MSS-SP-43, ASME/ANSI B16.9, ASME B16.28, BS4504, BS1560, BS10 |
| Size range | Buttweld: NPS ½ to 48 (DN 15 to DN 1200). Forged: NPS ⅛ to 4 (DN 6 to DN 100) |
| Wall thickness | Sch 5S, 10S, 40S, 80S, 160, XXS, STD, XS, matched to the pipe per ASME B36.19M / B36.10M |
| Ends | Bevel to ASME B16.25, plain end, socket weld, NPT threaded |
| Surface Finish | Pickled, Passivated, Polished (Ra 0.8 to Ra 3.2) |
| Heat treatment | Solution annealed, as required by ASTM A403 |
ASTM A403 WP304 Fittings vs 304L Stainless Steel Fittings vs WP304H: Picking the Grade
| Property | WP304 | WP304L | WP304H |
| UNS / Werkstoff Nr. | S30400 / 1.4301 | S30403 / 1.4307 (1.4306) | S30409 / 1.4948 |
| Carbon | 0.08% max | 0.030% max | 0.04 to 0.10% |
| Tensile strength, min | 515 MPa (75 ksi) | 485 MPa (70 ksi) | 515 MPa (75 ksi) |
| Yield strength, min | 205 MPa (30 ksi) | 170 MPa (25 ksi) | 205 MPa (30 ksi) |
| Weld zone sensitisation | Possible in the 425 to 815 °C (800 to 1500 °F) range | Greatly reduced by low carbon | Possible; grade chosen for strength, not weldability |
| Typical use | Unwelded or annealed assemblies | Field welded process and utility piping | Sustained service above about 525 °C, where design codes need the higher carbon for creep strength |
Dual certification. A fitting can meet both WP304 and WP304L when its carbon is at or below 0.030% and it meets the higher WP304 strength. It is then marked WP304/304L and accepted under either grade. Ask for it by name on the enquiry.
Chemical Composition of Stainless Steel 304 Fittings
| Element | WP304 | WP304L | WP304H |
| Carbon (C) | 0.08 max | 0.030 max | 0.04 to 0.10 |
| Manganese (Mn) | 2.00 max | 2.00 max | 2.00 max |
| Phosphorus (P) | 0.045 max | 0.045 max | 0.045 max |
| Sulphur (S) | 0.030 max | 0.030 max | 0.030 max |
| Silicon (Si) | 1.00 max | 1.00 max | 1.00 max |
| Nickel (Ni) | 8.0 to 11.0 | 8.0 to 12.0 | 8.0 to 11.0 |
| Chromium (Cr) | 18.0 to 20.0 | 18.0 to 20.0 | 18.0 to 20.0 |
| Nitrogen (N) | 0.10 max | 0.10 max | 0.10 max |
| Iron (Fe) | Balance | Balance | Balance |
Mechanical Strength of 304 Stainless Steel Fittings, Buttweld and Forged
| Grade | Tensile, min | Yield, min | Elongation, min | Reduction of area, min |
| 304 (WP304 / F304) | 515 MPa (75 ksi) | 205 MPa (30 ksi) | 28% L, 20% T (A403); 30% (A182) | Not specified (A403); 50% (A182) |
| 304L (WP304L / F304L) | 485 MPa (70 ksi) | 170 MPa (25 ksi) | 28% L, 20% T (A403); 30% (A182) | Not specified (A403); 50% (A182) |
| 304H (WP304H / F304H) | 515 MPa (75 ksi) | 205 MPa (30 ksi) | 28% L, 20% T (A403); 30% (A182) | Not specified (A403); 50% (A182) |
Physical Properties for 304/304L Buttweld Fittings
Typical annealed values. These are not specification limits.
| Property | Metric | Imperial |
| Density | 8.00 g/cm³ | 0.289 lb/in³ |
| Melting range | 1400 to 1450 °C | 2550 to 2650 °F |
| Modulus of elasticity | 193 GPa | 28.0 × 10⁶ psi |
| Mean thermal expansion, 0 to 100 °C | 17.2 µm/m·°C | 9.6 µin/in·°F |
| Thermal conductivity at 100 °C | 16.2 W/m·K | 9.4 BTU/h·ft·°F |
| Specific heat, 0 to 100 °C | 500 J/kg·K | 0.12 BTU/lb·°F |
| Electrical resistivity | 0.72 µΩ·m | 28.3 µΩ·in |
304 / 304L / 304H Equivalent Grades: UNS, Werkstoff, EN and JIS
| Grade | UNS | Werkstoff Nr. | EN name | JIS | BS |
| 304 | S30400 | 1.4301 | X5CrNi18-10 | SUS304 | 304S31 |
| 304L | S30403 | 1.4307 / 1.4306 | X2CrNi18-9 / X2CrNi19-11 | SUS304L | 304S11 |
| 304H | S30409 | 1.4948 | X6CrNi18-10 | SUS304H | 304S51 |
End user material specifications. Many operators and EPC contractors issue their own material specifications, with extra limits on chemistry, testing or marking. Send yours with the enquiry so the quotation is made against it.
Fitting Types: 304/304L Elbow, 304/304L Tee, 304/304L Reducer and More
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304/304L Buttweld Fittings Dimensions to ASME B16.9 (½" to 24")
Dimensions in mm, with inches in brackets. A = 90° long radius elbow centre to end. B = 45° elbow centre to end. C = equal tee centre to end. H = reducer end to end. E = cap length, standard wall.
| NPS | DN | OD at bevel | 90° LR elbow (A) | 45° elbow (B) | Equal tee (C) | Reducer (H) | Cap (E) |
| ½ | 15 | 21.3 (0.840) | 38 (1.50) | 16 (0.62) | 25 (1.00) | n/a | 25 (1.00) |
| ¾ | 20 | 26.7 (1.050) | 38 (1.50) | 19 (0.75) | 29 (1.12) | 38 (1.50) | 25 (1.00) |
| 1 | 25 | 33.4 (1.315) | 38 (1.50) | 22 (0.88) | 38 (1.50) | 51 (2.00) | 38 (1.50) |
| 1¼ | 32 | 42.2 (1.660) | 48 (1.88) | 25 (1.00) | 48 (1.88) | 51 (2.00) | 38 (1.50) |
| 1½ | 40 | 48.3 (1.900) | 57 (2.25) | 29 (1.12) | 57 (2.25) | 64 (2.50) | 38 (1.50) |
| 2 | 50 | 60.3 (2.375) | 76 (3.00) | 35 (1.38) | 64 (2.50) | 76 (3.00) | 38 (1.50) |
| 2½ | 65 | 73.0 (2.875) | 95 (3.75) | 44 (1.75) | 76 (3.00) | 89 (3.50) | 38 (1.50) |
| 3 | 80 | 88.9 (3.500) | 114 (4.50) | 51 (2.00) | 86 (3.38) | 89 (3.50) | 51 (2.00) |
| 4 | 100 | 114.3 (4.500) | 152 (6.00) | 64 (2.50) | 105 (4.12) | 102 (4.00) | 64 (2.50) |
| 6 | 150 | 168.3 (6.625) | 229 (9.00) | 95 (3.75) | 143 (5.62) | 140 (5.50) | 89 (3.50) |
| 8 | 200 | 219.1 (8.625) | 305 (12.00) | 127 (5.00) | 178 (7.00) | 152 (6.00) | 102 (4.00) |
| 10 | 250 | 273.0 (10.750) | 381 (15.00) | 159 (6.25) | 216 (8.50) | 178 (7.00) | 127 (5.00) |
| 12 | 300 | 323.8 (12.750) | 457 (18.00) | 190 (7.50) | 254 (10.00) | 203 (8.00) | 152 (6.00) |
| 14 | 350 | 355.6 (14.000) | 533 (21.00) | 222 (8.75) | 279 (11.00) | 330 (13.00) | 165 (6.50) |
| 16 | 400 | 406.4 (16.000) | 610 (24.00) | 254 (10.00) | 305 (12.00) | 356 (14.00) | 178 (7.00) |
| 18 | 450 | 457.0 (18.000) | 686 (27.00) | 286 (11.25) | 343 (13.50) | 381 (15.00) | 203 (8.00) |
| 20 | 500 | 508.0 (20.000) | 762 (30.00) | 318 (12.50) | 381 (15.00) | 508 (20.00) | 229 (9.00) |
| 24 | 600 | 610.0 (24.000) | 914 (36.00) | 381 (15.00) | 432 (17.00) | 508 (20.00) | 267 (10.50) |
Stub End Dimensions for 304/304L Stub Ends (mm, inches in brackets)
| NPS | Long pattern length, ASME B16.9 | Short pattern length, MSS SP-43 | Lap diameter G |
| ½ | 76 (3.00) | 51 (2.00) | 35 (1.38) |
| ¾ | 76 (3.00) | 51 (2.00) | 43 (1.69) |
| 1 | 102 (4.00) | 51 (2.00) | 51 (2.00) |
| 1½ | 102 (4.00) | 51 (2.00) | 73 (2.88) |
| 2 | 152 (6.00) | 64 (2.50) | 92 (3.62) |
| 3 | 152 (6.00) | 64 (2.50) | 127 (5.00) |
| 4 | 152 (6.00) | 76 (3.00) | 157 (6.19) |
| 6 | 203 (8.00) | 89 (3.50) | 216 (8.50) |
| 8 | 203 (8.00) | 102 (4.00) | 270 (10.62) |
| 10 | 254 (10.00) | 127 (5.00) | 324 (12.75) |
| 12 | 254 (10.00) | 152 (6.00) | 381 (15.00) |
Wall Thickness Schedules for 304L Seamless Pipe Fittings and Welded Fittings
A403 fittings are ordered to match the pipe wall. Values in mm, inches in brackets. Sch 5S, 10S, 40S and 80S follow ASME B36.19M. Sch 160 and XXS follow ASME B36.10M.
| NPS / DN | Sch 5S | Sch 10S | Sch 40S | Sch 80S | Sch 160 | XXS |
| ½ / 15 | 1.65 (0.065) | 2.11 (0.083) | 2.77 (0.109) | 3.73 (0.147) | 4.78 (0.188) | 7.47 (0.294) |
| ¾ / 20 | 1.65 (0.065) | 2.11 (0.083) | 2.87 (0.113) | 3.91 (0.154) | 5.56 (0.219) | 7.82 (0.308) |
| 1 / 25 | 1.65 (0.065) | 2.77 (0.109) | 3.38 (0.133) | 4.55 (0.179) | 6.35 (0.250) | 9.09 (0.358) |
| 1½ / 40 | 1.65 (0.065) | 2.77 (0.109) | 3.68 (0.145) | 5.08 (0.200) | 7.14 (0.281) | 10.15 (0.400) |
| 2 / 50 | 1.65 (0.065) | 2.77 (0.109) | 3.91 (0.154) | 5.54 (0.218) | 8.74 (0.344) | 11.07 (0.436) |
| 3 / 80 | 2.11 (0.083) | 3.05 (0.120) | 5.49 (0.216) | 7.62 (0.300) | 11.13 (0.438) | 15.24 (0.600) |
| 4 / 100 | 2.11 (0.083) | 3.05 (0.120) | 6.02 (0.237) | 8.56 (0.337) | 13.49 (0.531) | 17.12 (0.674) |
| 6 / 150 | 2.77 (0.109) | 3.40 (0.134) | 7.11 (0.280) | 10.97 (0.432) | 18.26 (0.719) | 21.95 (0.864) |
| 8 / 200 | 2.77 (0.109) | 3.76 (0.148) | 8.18 (0.322) | 12.70 (0.500) | 23.01 (0.906) | 22.23 (0.875) |
| 10 / 250 | 3.40 (0.134) | 4.19 (0.165) | 9.27 (0.365) | 12.70 (0.500) | 28.58 (1.125) | 25.40 (1.000) |
| 12 / 300 | 3.96 (0.156) | 4.57 (0.180) | 9.53 (0.375) | 12.70 (0.500) | 33.32 (1.312) | 25.40 (1.000) |
Seamless construction (WP-S) is normally made in the smaller sizes. Larger sizes are usually welded (WP-W, WP-WX or WP-WU). Confirm the class you need on the enquiry.
Where Stainless Steel 304/304L Pipe Fittings Work in GCC and Export Market Plants
| Sector | 304 / 304L service |
| Refining and petrochemicals | Instrument air, nitrogen, utility water, low chloride process streams |
| Gas processing and LNG | Cryogenic and low temperature lines, where austenitic toughness holds down to −196 °C (−320 °F) |
| Power and water | Demineralised water, condensate, treated water and dosing lines |
| Fertiliser | Selected nitric acid and urea plant services, per licensor material selection |
| Chemical processing | Oxidising acids, solvents and low chloride streams |
| Food, beverage and pharmaceutical | Process and CIP piping, with sanitary finish only where the order specifies it |
When SS 304 Fittings Are the Wrong Choice: Chlorides, Heat and Humidity
304 handles fresh water, oxidising acids, atmospheric exposure and many organic chemicals. It is weak against chlorides. Seawater, brine, desalination reject and coastal splash zones cause pitting, crevice attack and chloride stress corrosion cracking. Cracking risk rises steeply above about 60 °C (140 °F).
The destination environment matters in much of the Gulf. High ambient temperature, humid coastal air and salt-laden sand combine on outdoor piping, so 304 fittings exposed at the coast often pit within a few seasons. For marine and offshore and coastal service, use SS 316 pipe fittings or a higher alloy such as SS 904L pipe fittings. For continuous high temperature service, see SS 310 pipe fittings. For welded service in the sensitising range, see the stabilised SS 321 pipe fittings and SS 347 pipe fittings.
Certification and PMI: What a 304L Pipe Fittings Exporter Should Send with the Goods
ASTM A403 requires a test report for every fitting. Each fitting should carry grade, class, size, schedule and heat number so it can be traced to its certificate under EN 10204. The certificate level available, 3.1 or 3.2, is confirmed at quotation. If you need a 3.2 certificate, name your preferred third-party inspection agency on the enquiry.
Positive material identification (PMI) is worth asking for on any mixed grade order. 304L, 316L and 321 look identical in a laydown yard. Only a reading of chromium, nickel, molybdenum and titanium tells them apart. Ask for PMI on 100% of fittings where grades share a project. Availability is confirmed at quotation. Where the fittings will be welded and then exposed to acids, consider specifying intergranular corrosion testing to ASTM A262 Practice E.
Packing 304/304L Buttweld Fittings for Sea Freight and Site Laydown
Packing is agreed with each order. For sea freight and outdoor storage, typical requirements are:
- Bevel protectors or plastic end caps on every buttweld end
- Full separation from carbon steel in crates and on site, so free iron does not stain or contaminate the stainless surface
- Seaworthy wooden cases, with fittings tagged and packed by heat number
- Moisture barrier wrapping and desiccant for humid port storage
- Covered laydown away from sand, standing water, direct sun and coastal spray, with ends kept capped until fit up
Request a Quote for SS 304, 304L and 304H Pipe Fittings
Send your fitting list or material take-off with grades, sizes, schedules and quantities. Add the certificate level, any NACE or inspection requirement, your Incoterm and the destination port. Attach your project material specification if it sets extra requirements. A complete enquiry gets a complete quotation in the first reply.
Request a QuotationRelated Products for SS 304/304L Piping Systems
Matching material across the line simplifies PMI, welding procedures and paperwork. Build the system from pipe to fitting to flange in the same grade.
Pipes
- 304/304L pipes, stainless steel 304
- SS 304L pipe
- SS 304H pipe
- Stainless steel 304 seamless pipes
- Stainless steel 304 welded pipes
Pipe in 5.8 m and 11.8 m lengths fits standard 20 ft and 40 ft containers, which keeps sea freight simple. Confirm lengths at quotation.
Flanges (ASTM A182 F304 / F304L, ASME B16.5)
- SS 304 flanges: 304/304L weld neck flange, slip on flange and threaded flanges
- SS 304L flanges
- SS 304H flanges
For other stainless grades, return to the stainless steel pipe fittings range.
Buyer Questions on SS 304 Pipe Fittings and SS 304L Pipe Fittings
WP304 allows up to 0.08% carbon and has higher minimum strength: 515 MPa tensile and 205 MPa yield. WP304L limits carbon to 0.030%, which reduces sensitisation at welds, with minimums of 485 MPa tensile and 170 MPa yield. Dual certified WP304/304L fittings meet both grades.
Only within narrow limits. ISO 15156-3 accepts solution annealed 304 and 304L at 22 HRC maximum, at low temperature, low H2S partial pressure and low chloride content. Outside those limits a higher alloy is needed. Check the current edition of ISO 15156-3 for the exact limits.
No. Chlorides cause pitting and stress corrosion cracking in 304, especially above about 60 °C. Use 316L or a higher alloy for seawater, brine, desalination and coastal splash zones.
ASTM A403 covers the material of buttweld fittings and ASME B16.9 covers their dimensions. Forged socket weld and threaded fittings use ASTM A182 F304 or F304L, with dimensions and pressure classes to ASME B16.11.
The certificate level and inspection arrangements are confirmed at quotation. State 3.1 or 3.2, and the inspection agency you require, in your enquiry.
Grade, standard, fitting type, OD or NPS, wall schedule, quantity, end finish, certification level, inspection requirement, destination port and required date. A line list or material take-off is also fine.
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