What Is ASTM A403 WP304?
ASTM A403 is the specification for wrought austenitic stainless steel piping fittings. Grade WP304 is the standard 18Cr-8Ni stainless buttwelding fitting material for ASME B16.9 elbows, tees, reducers, caps and stub ends.
Temperature Range
WP304 fittings are rated up to 538°C, the stainless-steel pressure-temperature basis documented on our ASME B16.9 page.
Material Group (per ASME B16.5)
WP304 fittings pair with Group 2.1 (18Cr-8Ni) flanges in ASME B16.5 systems.
Corrosion Resistance
As with F304 forgings, the Schweitzer tables rate 304-type materials excellent to good in most neutral, oxidizing and organic media, unsatisfactory in concentrated hydrochloric and strong halide streams. Use WP316 for chloride service.
Typical Applications
- ASME B16.9 stainless buttwelding fittings, NPS 1/2–48
- Food, beverage, pharmaceutical and clean-water piping
- General chemical and utility stainless piping
Chemistry & Mechanical Properties
Composition and mechanical properties per ASTM A403 — consult the standard for exact limits. 3.1 mill certificates supplied.
Related Standards
- ASME B16.9 — Buttwelding Fittings (NPS 1/2–48)
- ASME B16.5 — Pipe Flanges
- ASTM A403 WP316 — Mo-Bearing Stainless Fittings
- ASTM A182 F304 — Stainless Forgings
- Buttwelding Elbows
- Equal Tees
FAQ
What temperature range does WP304 cover?
Up to 538°C per the stainless pressure-temperature basis of the ASME B16.9/B16.5 tables.
WP304 or WP304L?
WP304L is the low-carbon choice for heavily welded fabrication where post-weld annealing is not done.
Is WP304 suitable for seawater?
No — specify WP316 or duplex fittings for chloride-bearing service.
What schedules are available?
5S, 10S, 40S and 80S stainless schedules plus STD/XS, matching ASME B36.19 pipe.
What is the difference between WP304 and WP304L?
WP304L is the low-carbon variant for welded fabrication without post-weld annealing, keeping intergranular corrosion resistance.
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