Stainless Steel 304 / 304L
UNS S30400 / S30403 · The general-purpose austenitic grade
SS 304 is the most widely used stainless steel: an 18/8 austenitic grade with good corrosion resistance in atmospheric, freshwater and mild chemical service, excellent formability and straightforward welding. 304L, the low-carbon variant, is specified where the part is welded and heavy sections risk sensitisation.
When to specify SS 304
Choose 304 for general corrosion resistance, food and dairy contact, architectural work and indoor process piping. Move up to 316 when chlorides are present — seawater, coastal air, brines or chlorinated cleaning chemicals — because 304 is vulnerable to pitting in those conditions.
Chemical Composition (%)
Composition and mechanical values are the limits set by the governing ASTM specification and are given for reference. The mill test certificate supplied with your consignment carries the actual heat analysis.
| Element | 304 (S30400) | 304L (S30403) |
|---|---|---|
| Carbon | 0.08 max | 0.030 max |
| Chromium | 18.0 – 20.0 | 18.0 – 20.0 |
| Nickel | 8.0 – 10.5 | 8.0 – 12.0 |
| Manganese | 2.00 max | 2.00 max |
| Silicon | 0.75 max | 0.75 max |
| Phosphorus | 0.045 max | 0.045 max |
| Sulphur | 0.030 max | 0.030 max |
| Nitrogen | 0.10 max | 0.10 max |
Mechanical & Physical Properties
| Property | 304 | 304L |
|---|---|---|
| Tensile strength | 515 MPa min | 485 MPa min |
| Yield strength (0.2%) | 205 MPa min | 170 MPa min |
| Elongation in 50 mm | 40% min | 40% min |
| Hardness | 201 HB / 92 HRB max | 201 HB / 92 HRB max |
| Density | 8.00 g/cm³ | 8.00 g/cm³ |
Governing Standards
| Standard | Covers |
|---|---|
| ASTM A312 / A358 | Seamless and welded pipe |
| ASTM A213 / A269 | Tube |
| ASTM A240 | Plate, sheet and coil |
| ASTM A276 / A479 | Bar and shapes |
| ASTM A403 WP304/304L | Buttweld fittings |
| ASTM A182 F304/F304L | Forged fittings and flanges |
Equivalent Designations
| Standard | Designation |
|---|---|
| EN | 1.4301 (304) / 1.4307 (304L) |
| JIS | SUS 304 / SUS 304L |
| GB | 06Cr19Ni10 / 022Cr19Ni10 |
| UNS | S30400 / S30403 |
Typical Applications
- Process and utility piping in mild service
- Food, dairy and beverage plant
- Architectural cladding, railings and structural trim
- Heat exchanger and condenser tubing in freshwater
- Tanks, vessels and general fabrication
Industries Served
- Food & Dairy
- Pharmaceutical
- Construction
- Water Treatment
- Engineering
SS 304 Products We Supply
Available in the forms below, minimum order quantity 5 kg, with a mill test certificate to EN 10204 3.1 traceable to the heat number.
- SS 304 Pipes & Tubes→
- SS 304 Buttweld Fittings→
- SS 304 Forged Socketweld & Screwed Fittings→
- SS 304 Flanges→
- SS 304 Sheets, Plates & Coils→
- SS 304 Fasteners & Nut Bolts→
- SS 304 Valves→
- SS 304 Round, Square & Hex Bars→
- SS 304 Dairy Fittings→
- SS 304 Stainless Steel Bends→
- SS 304 Stainless Steel Flats→
- SS 304 Channels & Angles→
Need SS 304 in a form not listed above? We source to requirement — and we will confirm availability and lead time.
SS 304 by product form
Governing standards, dimensions and stock availability for each form.
SS 304 — Frequently Asked Questions
- What is the difference between 304 and 304L?
- 304L limits carbon to 0.030% against 0.08% for 304. The lower carbon reduces the risk of chromium carbide precipitation at grain boundaries during welding — sensitisation — which would otherwise leave the heat-affected zone vulnerable to intergranular corrosion. Specify 304L for welded heavy sections; 304 is adequate for thin sections and non-welded parts. 304L has slightly lower strength as a result.
- Is SS 304 suitable for seawater?
- No. Chlorides attack the passive layer on 304 and cause pitting and crevice corrosion. For seawater and chloride-bearing service use 316/316L, and for higher chloride levels or higher temperatures use Duplex 2205 or a super duplex grade.
- Is SS 304 magnetic?
- In the annealed condition 304 is essentially non-magnetic. Cold working — bending, drawing, machining — transforms some austenite to martensite and can make the part weakly magnetic. This is normal and does not indicate the wrong grade has been supplied.
Send your SS 304 requirement
Tell us the form, size, quantity and standard and our technical team will confirm stock and send a firm price. Minimum order quantity 5 kg, mill test certificates supplied as standard.