304/304L Stainless Steel Flanges
Filters
Quick filters
List of products
304 / 304L flanges for general-purpose systems
1.4301 (AISI 304) is the most widely used austenitic stainless steel: about 18% chromium and 8–10% nickel, with no molybdenum. Flanges in this category are dual-certified 1.4301 / 1.4307 (304 / 304L) – the material meets the requirements of both grades, and the low carbon of the L version limits the risk of intergranular corrosion after welding. It is a good choice for potable and process water, compressed air, food, brewery and ventilation systems, and for media with low chloride content.
Chemical composition of 1.4301 / 1.4307
| Grade | C | Cr | Ni | Mo |
|---|---|---|---|---|
| 1.4301 / 304 | ≤ 0.07 | 17.5–19.5 | 8.0–10.5 | – |
| 1.4307 / 304L | ≤ 0.030 | 17.5–19.5 | 8.0–10.5 | – |
Values in wt. % per EN 10088. Equivalents: 1.4301 = X5CrNi18-10 = UNS S30400, 1.4307 = X2CrNi18-9 = UNS S30403; forgings per ASTM A182 – F304 / F304L.
Types and sizes: PN and Class 150
Metric flanges per EN 1092-1 include weld neck flanges from DN15 to DN300, slip-on plate flanges from DN15 to DN150 and loose (lap joint) flanges from DN15 to DN150, rated PN10, PN16 and PN40. A loose flange bears against a flared pipe end or a welded-on collar and rotates freely, which makes bolt-hole alignment easier. For inch-size systems we carry 13 Class 150 weld neck flanges per ASME B16.5 from ½″ to 8″ (21.3–219.1 mm), bored for Sch 40S pipe. PN and Class flanges cannot be mated – their bolt patterns differ.
When 304 is not enough
304 contains no molybdenum, so in seawater, brines, swimming pools and other chloride environments it can suffer pitting and crevice corrosion – especially under the gasket, where the medium stagnates. Such conditions call for 316L. For systems running at elevated temperatures, such as steam lines, titanium-stabilized 321 is a better fit.
Matching pipe and fittings
To go with 304 flanges, choose 304 / 1.4301 pipe & tube and 304 / 1.4301 elbows. Where chlorides are present, select 316L / 1.4404 flanges, and for steam and higher temperatures, 321 / 1.4541 flanges. All types are in the Flanges category.