ASTM A403 WP304 Stainless Steel Fittings – WP304-S / W / WX Buttweld Fittings
ASC LLP, Mumbai, supplies ASTM A403 WP304 stainless steel fittings: seamless and welded buttweld elbows, tees, reducers, caps and stub ends to ASME B16.9, from ½” to 48″. In addition, every fitting is supplied with an EN 10204 3.1 certificate. See also our full range of stainless steel fittings.
What are ASTM A403 WP304 Fittings?
ASTM A403 (ASME SA403) covers wrought austenitic stainless steel piping fittings for pressure service. WP304 is the fitting grade in 18Cr-8Ni stainless steel (UNS S30400), made from seamless or welded pipe, plate or forgings and formed to buttweld shapes. Consequently, WP304 fittings are the standard match for ASTM A312 TP304 pipe.
WP304 is the most widely used stainless fitting grade, because it offers good corrosion resistance in water, food and mild chemicals at a lower cost than WP316. For chlorides, however, the molybdenum in 316 is needed. Note that forged socket-weld and threaded fittings are not A403 products; instead, they are ordered as A182 F304.
A403 WP304 Fittings – Quick Facts
- Specification: ASTM A403 / ASME SA403, Grade WP304 (UNS S30400)
- Classes: WP304-S, -W, -WX and -WU; in addition, CR for light-wall fittings
- Composition: 18–20% Cr and 8–11% Ni
- Dimensions: ASME B16.9 and B16.28, as well as MSS SP-43
- Strength: 515 MPa tensile, while yield is 205 MPa min
- Matching pipe: ASTM A312 TP304
Key Properties of A403 WP304 Fittings
- Corrosion resistance: good in fresh water, steam, food products and many mild chemicals.
- Hygiene: smooth, non-porous surfaces, so WP304 is widely used in food and dairy lines.
- Toughness: austenitic, therefore it stays tough down to cryogenic temperatures.
- Weldability: welds easily with 308 filler; however, WP304L is preferred where welds see corrosive service.
- Limitation: chlorides can cause pitting and stress corrosion cracking, which is when 316 or duplex is used.
Types of A403 WP304 Buttweld Fittings
- Elbows: 45°, 90° and 180°, in long radius (1.5D) and short radius (1D), as well as 3D / 5D bends.
- Tees and crosses: equal and reducing.
- Reducers: concentric for vertical lines and, similarly, eccentric for pump suctions.
- Caps and stub ends: end closures, in addition to stub ends for lap-joint flanges.
A403 WP304 Fitting Sizes & Schedules
| Size range (NPS) | Typical schedules |
| ½” – 2″ | 5S, 10S, 40S, 80S, 160, XXS |
| 2½” – 12″ | 5S, 10S, 40S, 80S, 120, 160, XXS |
| 14″ – 24″ | 5S, 10S, 20, 40S, 80S |
| 26″ – 48″ | welded, to required wall thickness |
Fitting dimensions follow ASME B16.9; meanwhile, short-radius elbows follow B16.28 and light-wall fittings follow MSS SP-43. The wall thickness is matched to the connecting pipe schedule.
A403 WP304 Mechanical Properties
| Property | A403 WP304 |
| Tensile strength, min | 515 MPa (75 ksi) |
| Yield strength (0.2%), min | 205 MPa (30 ksi) |
| Elongation, min | 28% (longitudinal) |
| Hardness | Not specified in A403 |
A403 does not set a hardness limit for WP304. Therefore, a hardness requirement, if needed, must be added to the purchase order.
A403 WP304 Fittings Specifications
| Item | Details |
| Specification | ASTM A403 / ASME SA403, Grade WP304 |
| Classes | S (seamless); W, WX and WU (welded); CR (light wall) |
| Heat treatment | Solution annealed at 1040 °C (1900 °F) min, then rapidly cooled |
| Dimensions | ASME B16.9, B16.28; alternatively, MSS SP-43 |
| Ends | Bevelled to ASME B16.25 |
| Certificate | EN 10204 3.1; in addition, 3.2 and third-party inspection on request |
For welded fittings, WP304-W covers radiography of the fitting maker’s welds, while WP304-WX requires radiography of all welds and WP304-WU ultrasonic examination of all welds. Hence, the class should always be stated on the order.
ASTM A403 WP304 Chemical Composition
| Element | WP304 (%) |
| Carbon (C) | 0.08 max |
| Manganese (Mn) | 2.00 max |
| Phosphorus (P) | 0.045 max |
| Sulphur (S) | also 0.030 max |
| Silicon (Si) | 1.00 max |
| Chromium (Cr) | 18.0 – 20.0 |
| Nickel (Ni) | 8.0 – 11.0 |
| Iron (Fe) | Balance |
WP304 is an 18Cr-8Ni stainless steel; the chromium forms the protective passive film, while nickel keeps the structure austenitic.
WP304 vs WP304L vs WP304H vs WP316
| Grade | Carbon (%) | Main feature | Typical choice |
| WP304 | 0.08 max | 18Cr-8Ni | General service, at the lowest cost |
| WP304L | 0.030 max | Low carbon, so welds resist sensitisation | Welded lines in corrosive service |
| WP304H | 0.04 – 0.10 | Higher carbon for creep | Hot service, especially above about 500 °C |
| WP316 | 0.08 max | Adds 2–3% Mo | Chloride-bearing service |
Many fittings are dual certified WP304/304L. For stabilised grades, see A403 WP321 fittings and the A403 WP fittings overview.
Applications of ASTM A403 WP304 Fittings
| Industry | Typical WP304 fitting use |
| Food & dairy | Process and CIP lines, often with polished bores |
| Water & utilities | Potable water, demineralised water and steam lines |
| Chemical processing | Mild chemical and solvent lines, while chlorides stay low |
| Pharmaceutical | Purified water and utility piping |
| Cryogenic | LNG and liquid gas lines, because 304 stays tough at low temperature |
Matching items include 304 pipe, 304L pipe and 304 flanges. Welding WP304 directly to carbon steel pipe, however, needs a dissimilar-metal procedure, typically with 309 filler.
Why Buy A403 WP304 Fittings from ASC LLP?
- Traceable material: EN 10204 3.1 certificates with heat number, class and test results.
- Correct grade advice: help choosing WP304, WP304L or WP316, because the fluid and welding decide the grade.
- Complete packages: fittings together with pipe and flanges in the same grade.
- Export packing: finally, fittings are end-capped and packed in wooden cases.
For the general grade page, see our stainless steel 304 fittings.
Frequently Asked Questions – ASTM A403 WP304 Fittings
What is ASTM A403 WP304?
In short, it is a wrought 304 stainless steel buttweld fitting made to ASTM A403, normally to ASME B16.9 dimensions.
What is the chemical composition of WP304?
WP304 contains Cr 18.0–20.0%, Ni 8.0–11.0%, C 0.08% max, Mn 2.00% max, Si 1.00% max, P 0.045% max and S 0.030% max.
What are the mechanical properties of A403 WP304?
It needs 515 MPa tensile and 205 MPa yield minimum, with 28% elongation. However, A403 sets no hardness limit.
What is the difference between WP304 and WP304L?
WP304L limits carbon to 0.030%, so welds resist sensitisation. As a result, dual-certified WP304/304L fittings are common.
Are A403 WP304 fittings forged?
No. They are wrought buttweld fittings formed from pipe, plate or forgings. By contrast, forged socket-weld fittings are ordered as A182 F304.
What does WP304-W mean?
It is a welded fitting with the fitting maker’s welds radiographed. WX means all welds are radiographed, while WU means all welds are ultrasonically examined.
When should WP316 be used instead of WP304?
Whenever chlorides are present, for example in seawater or brine, because 316 resists pitting better.
Global Supply
ASC LLP supplies ASTM A403 WP304 stainless steel fittings from Mumbai to customers in India, the Middle East, Europe, Africa, the Americas and South-East Asia. To get a prompt quotation, simply send your enquiry with fitting type, size, schedule, class and quantity.
Countries We Export To
UNITED STATES, EUROPE, UK, UAE, SAUDI ARABIA, OMAN, KUWAIT, JORDAN, QATAR, INDONESIA, MALAYSIA, BRAZIL, SPAIN, ITALY, FRANCE, GERMANY, BAHRAIN, SRI LANKA, AZERBAIJAN, AUSTRALIA, AUSTRIA, PHILIPPINES, TURKEY, RUSSIA, IRAN, IRAQ, CANADA, KOREA, JAPAN, YEMEN, FINLAND, ZIMBABWE, HUNGARY, PORTUGAL, VIETNAM, MOROCCO, THAILAND, SOUTH AFRICA, MEXICO, SINGAPORE, GREECE, KUWAIT, POLAND, NEW ZEALAND, SWEDEN, SWITZERLAND, BELGIUM, BHUTAN, BANGLADESH, TAIWAN, ROMANIA, CAMBODIA, KAZAKHSTAN, AFGHANISTAN.
