303 Stainless Steel is a commonly used engineering material. This page provides a complete data sheet including composition, mechanical properties, thermal properties, and typical applications. Use this information for material selection, engineering design, and comparison with similar grades.
Stainless steel type 1.4305 is popularly known as grade 303 stainless steel. Grade 303 is the most readily machineable of all the austenitic grades of stainless steel. The machineable nature of grade 303 is due to the presence of Sulphur in the steel composition. Whilst the Sulphur improves machining, it also causes a decrease in the corrosion resistance and a slight lowering of the toughness. The corrosion resistance of type 303 is lower than that for 304. The toughness is still excellent as with other austenitic grades.
Grade 303 is used in applications that require parts to be heavily machined. These applications include: Nuts and bolts, Screws, Gears, Aircraft fittings, Bushings and Shafts.
Type 303 is not readily cold workable. Some cold working is possible but sharp bending should not be attempted.
Sulphur additions to the composition act as initiation sites for pitting corrosion. This decreases the corrosion resistance of 303 stainless steel to less than that for 304. However. corrosion resistance remains good in mild environments. In chloride containing environments over 60°C, 303 stainless steel is subject to pitting and crevice corrosion. Grade 303 stainless is not suitable for use in marine environments.
Fabrication of all stainless steels should be done only with tools dedicated to stainless steel materials. Tooling and work surfaces must be thoroughly cleaned before use. These precautions are necessary to avoid cross contamination of stainless steel by easily corroded metals that may discolour the surface of the fabricated product.
Grade 303 stainless steel has good resistance to oxidation when intermittently exposed to temperature up to 760°C temperatures. It also has good oxidation resistance in continuous service to 870°C. This, however, is not recommended as 303 is sensitive to carbide precipitation with continuous use at 425-860°C.
Grade 303 stainless steel cannot be hardened by heat treatment. Solution treatment or annealing can be done by rapid cooling after heating to 1010-1120°C.
Fabrication methods, like forging, that involve hot working like should occur after uniform heating to 1149-1260°C. The fabricated components should then be rapidly cooled to ensure maximum corrosion resistance.
Grade 303 stainless steel has excellent machinability. Machining can be enhanced by adhering to the following rules: Cutting edges must be kept sharp. Dull edges cause excess work hardening. Cuts should be light but deep enough to prevent work hardening by riding on the surface of the material. Chip breakers should be employed to assist in ensuring swarf remains clear of the work Low thermal conductivity of austenitic alloys results in heat concentrating at the cutting edges. This means coolants and lubricants are necessary and must be used in large quantities.
The sulphur addition present in 303 stainless steel results in poor weldability. If 303 must be welded the recommended filler rods or electrodes are grades 308L and 309 stainless steels. For maximum corrosion resistance, the welds must be annealed.
Stainless Steel Grade 1.4305/303 also corresponds to the following designations but may not be a direct equivalent: UNS S30300, BS 303S31, EN 58M
Carbon (C) 0.0 - 0.10
Chromium (Cr) 17.00 - 19.00
Manganese (Mn) 0.0 - 2.00
Silicon (Si) 0.0 - 1.00
Phosphorous (P) 0.0 - 0.05
Sulphur (S) 0.15 - 0.35
Nickel (Ni) 8.00 - 10.00
Copper (Cu) 0.0 - 1.00
Nitrogen (N) 0.0 - 0.11
Iron (Fe) Balance
| Metric | Imperial | |
|---|---|---|
| Dielectric Strength | ∞V/m | ∞V/ft |
| Electric Resistivity (@ 20 °C) | 74 µΩcm | 29.08 µΩin |
| Magnetic Permeability | 1.02 | 1.02 |
| Metric | Imperial | |
|---|---|---|
| Ductility | 50 % | 50 % |
| Friction Coefficient (static) | 0.06-0.15 | 0.06-0.15 |
| Hardness, Rockwell B | 85 | 85 |
| Poissons Ratio | 0.29 | 0.29 |
| Proof Stress | 200 Mpa | 29007.54 psi |
| Mass Density | 8030 Kg/m3 | 501.30 lb/ft3 |
| Shear Modulus | 77 Gpa | 11167.90 ksi |
| Tensile Strength | 620 MPa | 89923.37 psi |
| Yield Strength | 240 MPa | 34809.05 psi |
| Youngs Modulus | 193 GPa | 27992.28 ksi |
| Metric | Imperial | |
|---|---|---|
| Coefficient of Thermal Expansion (Linear @ 0-100°C) | 17.3 x 10-6 °C-1 | 9.62 x 10-6 °F-1 |
| Melting Point | 1400 °C | 2552.00-32.00 °F |
| Service Temperature in Air Intermittent | 760 °C | 1400.00 °F |
| Service Temperature in Air Continous | 870 °C | 1598.00 °F |
| Specific Heat Capacity | 0.5 J/g-°C | 207.80 BTU/lb-°F |
| Thermal Conductivity | 15 W/mK | 8.67 BTU/hr ft |