303
Data verified303 is the free-machining version of 304, with sulfur (and often phosphorus) added to break chips. It is the standard bar grade for high-volume turned parts, at the cost of reduced corrosion resistance and weldability.
Chemical composition
| Element | Content (%) |
|---|---|
| C | ≤0.15 |
| Si | ≤1.00 |
| Mn | ≤2.00 |
| P | ≤0.20 |
| S | ≥0.15 |
| Cr | 17.00–19.00 |
| Ni | 8.00–10.00 |
| Mo | ≤0.60 (optional) |
Weight percent, per the governing standard ranges. Actual values per heat are on the mill certificate.
Properties
| Delivery condition | Annealed |
| Hardness | ≤262 HB (annealed) |
| Tensile strength | 515–690 MPa |
| Density | 7.90 g/cm³ |
Heat treatment
Solution anneal 1010–1120 °C, rapid cool. Not hardenable by heat treatment.
Equivalent grades
| Standard | Designation |
|---|---|
| din | 1.4305 |
| aisi | 303 |
| jis | SUS303 |
| gb | Y12Cr18Ni9 |
Compare side by side: 303 vs 304
Equivalents overlap in chemistry and use but are not always identical — see our equivalents guide before substituting in certified designs.
Applications & Processing
Applications: Shafts, valve bodies, fittings, fasteners, screw-machine parts, pump components.
Processing: Best machinability of the austenitic family; welding is not recommended because sulfur promotes hot cracking; corrosion resistance is below 304, especially in welds.
FAQ
- Why should 303 not be welded?
- The sulfur that makes it free-machining also causes hot cracking and weak, corrosion-prone weld metal. For welded parts use 304 or 304L instead.
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Ask for a quotationVisit NasteelSource: ASTM A276 / EN 10088 published ranges · Last updated 2026-11-03. Data is indicative — verify critical values against the governing standard and mill certificate before use.