SS 304L: properties, composition, uses and standards
SS 304L is a low-carbon austenitic chromium-nickel stainless steel, chosen for welded tanks, piping and vessels in general corrosive service. UNS S30403, W.Nr 1.4307, PREN ≈ 18, density 8 g/cm³.
What is SS 304L?
SS 304L is a low-carbon austenitic chromium-nickel stainless steel. Engineers choose it for welded tanks, piping and vessels in general corrosive service. It is also known as AISI 304L, UNS S30403, W.Nr 1.4307, Low-carbon 304.
- UNS
- S30403
- W.Nr
- 1.4307
- EN
- X2CrNi18-9
- JIS
- SUS 304L
- BS
- 304S11
- Density
- 8 g/cm³
- Melting range
- 1400 – 1450 °C
- Magnetic
- Non-magnetic annealed
- PREN (approx.)
- ≈ 18
Chemical composition and what each element does
| Element | Weight % |
|---|---|
| Chromium | 17.5 – 19.5 |
| Nickel | 8.0 – 12.0 |
| Carbon | 0.030 max |
| Manganese | 2.00 max |
| Silicon | 0.75 max |
| Nitrogen | 0.10 max |
| Phosphorus | 0.045 max |
| Sulphur | 0.030 max |
| Iron | Balance |
Per ASTM A240 for UNS S30403.
About 18% chromium forms the passive film that makes the steel stainless.
Nickel keeps the structure austenitic — tough at low temperature and easy to form and weld.
0.030% carbon max stops carbide forming at grain boundaries during welding, so heavy welds keep their corrosion resistance.
Most mill material today is dual-certified 304/304L, meeting the strength of 304 and the carbon limit of 304L.
SS 304L at a glance
See the SS 304L product page for every form we supply and its standard.
Mechanical properties
| Property | Value |
|---|---|
| Tensile strength | 485 MPa · 70 ksi |
| Yield strength 0.2% | 170 MPa · 25 ksi |
| Elongation | 40% |
| Hardness | 201 HB max |
Annealed plate & sheet, minimum values. Values for pipe, bar and forgings differ slightly — see the product standard.
Where SS 304L is used
- Process piping. Welded lines in chemical and pharma plants. Industry →
- Storage tanks. Welded tanks for water, chemicals and food. Industry →
- Cryogenic service. Tough down to very low temperatures. Industry →
- Pharmaceutical. Utility piping and vessels. Industry →
Welding 304L
The matching filler is ER308L (AWS A5.9). ER309L for dissimilar joints.
Keep heat input moderate and interpass temperature low, clean joints thoroughly, and pickle or passivate after welding where the service is corrosive.
SS 304L compared with similar grades
| Grade | PREN | Choose it for |
|---|---|---|
| SS 304L | ≈ 18 | Welded tanks, piping and vessels in general corrosive service |
| SS 304 | ≈ 18 | General corrosion resistance, food, water and architectural work |
| SS 316 / 316L | ≈ 24 | Chloride-bearing process fluids, marine air and pharmaceutical service |
| Duplex 2205 | ≈ 35 | Strength with chloride resistance at a stainless-steel budget |
SS 304L standards by product
Buying SS 304L: what to specify
- The product standard and the UNS or designation — for example ASTM A240 UNS S30403.
- Size, thickness or schedule, and quantity in pieces and kg or metres.
- Heat-treatment condition where the standard offers a choice.
- Certificate: EN 10204 3.1 as standard, 3.2 if a third party must witness.