303
1.4305Free-machining austenitic stainless steel — the most machinable of all austenitic grades. 0.15-0.35% S (as MnS inclusions) provides excellent chip-breaking. Trade-off: lower corrosion resistance than 304, poor weldability (hot cracking risk), and not suitable for cold forming. Used for high-volume automatic lathe parts: fittings, valves, screws, shafts, and precision components.
International equivalents
| Flag | Standard | Country | Grade | Number | Match |
|---|---|---|---|---|---|
| 🇺🇸 | AISI | USA | AISI 303 / UNS S30300 | S30300 | REF |
| 🇪🇺 | EN | Europe | X8CrNiS18-9 (1.4305) | 1.4305 | 100% |
| 🇬🇧 | BS | United Kingdom | 303S31 / EN 58M | — | 95% |
Sources: ASTM A582, EN 10088-3, BS 970
Chemical composition comparison (wt%)
Side-by-side: 303 (EN) (EN 10088-3) vs 303S31 / EN 58M (BS)
| Element | 303 (EN) | 303S31 / EN 58M (BS) | Overlap |
|---|---|---|---|
| C | 0–0.1% | — | — |
| Si | 0–1% | — | — |
| Mn | 0–2% | — | — |
| P | 0–0.045% | — | — |
| S | 0.15–0.35% | — | — |
| Cr | 17–19% | — | — |
| Ni | 8–10% | — | — |
Mechanical properties
Solution annealed
| Property | Value | Unit |
|---|---|---|
| Tensile Strength | 500–750 | MPa |
| Yield Strength | ≥ 190 | MPa |
| Elongation | ≥ 35 | % |
| Hardness HB | ≤ 230 | HB |
| Elastic Modulus | ≥ 200 | GPa |
| Density | ≥ 7.9 | g/cm3 |
Compatibility verdict
303 and 303S31 / EN 58M: 95% composition match
Close equivalents but NOT identical.
Related materials
304 Stainless Steel
1.4301The most widely used austenitic stainless steel. Excellent corrosion resistance, good formability and weldability. Standard choice for food processing, chemical, and architectural applications.
316L
1.4404Low-carbon austenitic stainless steel with molybdenum addition. Superior corrosion resistance to 304, especially against chlorides and pitting. Standard choice for chemical processing, marine, medical implants, and pharmaceutical equipment.
430 Stainless Steel
1.4016Ferritic chromium stainless steel with good corrosion resistance and formability. Lower cost than austenitic grades. Used for automotive trim, kitchen sinks, architectural panels, and appliance components.
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