Guides/Comparisons
303 vs 304 stainless steel
303-vs-304-stainless-steelStainless steel 303 and Stainless steel 304 at a glance
This page compares Stainless steel 303 and Stainless steel 304 using only values that carry a source, a test condition and an evidence level. Ranges run across temper, heat treatment and product form, measured at room temperature where the source says so.
- Composition: Chromium (303 17 to 19%; 304 18 to 20%), Nickel (303 8 to 10%; 304 8 to 11%), Carbon (303 up to 0.15%; 304 up to 0.08%), Phosphorus (303 up to 0.2%; 304 up to 0.045%).
- Yield strength: the ranges overlap (303 172 to 207 MPa; 304 at least 205 MPa).
- Tensile strength: the ranges overlap (303 500 to 517 MPa; 304 at least 515 MPa).
- Density: the ranges overlap (303 7.89 to 8.03 g/cm³; 304 7.85 to 8.06 g/cm³).
- Young's modulus: the ranges overlap (303 193 to 200 GPa; 304 200 GPa).
- Thermal conductivity: the ranges overlap (303 15 W/(m·K); 304 14 to 17 W/(m·K)).
- Melting point: the ranges overlap (303 1,400 to 1,455 °C; 304 1,400 to 1,450 °C).
"Higher" means the whole range is higher, not just one value. Where a value is a specified minimum, the table says "at least".
Side by side
| Property | Stainless steel 303 | Stainless steel 304 |
|---|---|---|
| Yield strength | 172 to 207 MPa | at least 205 MPa |
| Tensile strength | 500 to 517 MPa | at least 515 MPa |
| Density | 7.89 to 8.03 g/cm³ | 7.85 to 8.06 g/cm³ |
| Young's modulus | 193 to 200 GPa | 200 GPa |
| Thermal conductivity | 15 W/(m·K) | 14 to 17 W/(m·K) |
| Melting point | 1,400 to 1,455 °C | 1,400 to 1,450 °C |
| Thermal expansion | 17.3 ppm/K | no data |
Composition
| Element | Stainless steel 303 | Stainless steel 304 |
|---|---|---|
| Iron | balance | balance |
| Chromium | 17 to 19% | 18 to 20% |
| Nickel | 8 to 10% | 8 to 11% |
| Carbon | up to 0.15% | up to 0.08% |
| Manganese | up to 2% | up to 2% |
| Silicon | up to 1% | up to 1% |
| Phosphorus | up to 0.2% | up to 0.045% |
| Sulphur | 0.15% | up to 0.03% |
| Molybdenum | up to 0.6% | not listed |
Shares are as printed in the sources, by weight.
When to use which
| Material | Best for | Weakest at |
|---|---|---|
| Stainless steel 303 | Heavily machined parts in mild service, such as screws, nuts, bolts, shafts and fittings (Aalco, UPMET) | Chloride and marine service, where Aalco says 303 is not suitable, and welded joints, where Aalco says weldability is poor |
| Stainless steel 304 | Corrosion-resistant housings, fasteners and tanks where ordinary steel would rust | Chloride pitting in acidic solutions, and low strength compared with precipitation-hardened steels |
Where each is used
| Material | Use |
|---|---|
| Stainless steel 303 | Nuts, bolts and screws |
| Stainless steel 303 | Aircraft fittings |
| Stainless steel 303 | Shafts, gears and bushings |
| Stainless steel 303 | Automatic screw machine parts |
| Stainless steel 304 | Spacecraft propellant tank |
| Stainless steel 304 | Fasteners and screws |
| Stainless steel 304 | Architectural cladding |