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SUS303
ISO M (stainless steel)Stainless steel bars (austenitic, free-machining). Standard: JIS G 4303.
🌐International equivalents
“Close” means composition or properties are not exactly the same. Before substituting, check the values in each standard.
| System | Designation | Number | Relation | Confidence |
|---|---|---|---|---|
| JIS | SUS303 | JIS G 4303 | — | |
| AISI | 303 | UNS S30300 | equivalent | Agrees in 2+ sources[9][8][10][11] |
| EN | X8CrNiS18-9 | 1.4305 | close | Agrees in 2+ sources[8][10][9] |
| ISO | X10CrNiS18-9ISO 15510 number 4305-303-00-I | 4305-303-00-I | close | Agrees in 2+ sources[9][10] |
| GB | Y12Cr18Ni9former grade Y1Cr18Ni9; the unified numerical code in the Japan Stainless Steel Association's table is S30317 | S30317 | close | One source / reference[11][9] |
Differences between the equivalents (from the sources)
- EN X8CrNiS18-9: 1.4305 in EN 10088-3 has C ≤0.10, P ≤0.045, S 0.15–0.35 and Cu ≤1.0, so its ranges differ from JIS (C ≤0.15, P ≤0.20, S ≥0.15). The designation X10CrNiS18-9 in the Japan Stainless Steel Association's table is an ISO 15510 designation
- GB Y12Cr18Ni9: Kyocera's comparison table places the former grade Y1Cr18Ni9 in the same row as SUS303. The correspondence between the new grade Y12Cr18Ni9 and S30317 could not be confirmed in primary sources (S30317 appears only in the Japan Stainless Steel Association's table)
⚗Chemical composition (mass %)
As specified in JIS (Japan Stainless Steel Association JIS steel grade composition table / Nippon Steel stainless steel bars)
| Element | Range | Confidence |
|---|---|---|
| C | ≤ 0.15 | Agrees in 2+ sources[1][2] |
| Si | ≤ 1 | Agrees in 2+ sources[1][2] |
| Mn | ≤ 2 | Agrees in 2+ sources[1][2] |
| P | ≤ 0.2 | Agrees in 2+ sources[1][2] |
| S | ≥ 0.15 | Agrees in 2+ sources[1][2] |
| Ni | 8 – 10 | Agrees in 2+ sources[1][2] |
| Cr | 17 – 19 | Agrees in 2+ sources[1][2] |
| Mo | May contain up to 0.60% (optional addition) | Agrees in 2+ sources[1][2] |
⚖Density
7.9 g/cm³
One source / reference[8]
Value of DEW (EN 1.4305): 7.9 kg/dm³. No Japanese primary source was found for SUS303
Calculate weight in SUS303 →💪Mechanical properties
“Reference” values are not specified minimums from the standard but figures published by makers and others.
| Condition | Tensile MPa | Yield MPa | Elong. % | Hardness | Type of value |
|---|---|---|---|---|---|
| Bars (JIS G 4303) solution heat treated 1010–1150℃, rapid cooling | ≥ 520 | ≥ 205 | ≥ 40 | HBW 187 max / HRBW 90 max / HV 200 max | JIS specified value (as listed in the Sanyo Special Steel and Aichi Steel catalogs) Agrees in 2+ sources[6][7] |
1 MPa ≈ 145 psi (0.145 ksi). Hardness conversion · unit converter
🔧Machinability notes (as stated in the sources)
- Free-machining stainless steel containing 0.15% or more S. In the Japan Stainless Steel Association's machinability comparison, SUS303 is in the high-machinability group among the austenitic grades (SUS304 is in the low group)[12][1]
- DEW describes 1.4305 as a representative austenitic steel for automatic lathe machining and rates its machinability "sehr gut" (very good) and its weldability and forgeability "schlecht" (poor). Because of the sulfur addition, pitting and similar attack are possible in acid and chloride environments, and its corrosion resistance is inferior to 1.4301[8]
- In Daido Steel's drill life test (SKH51 φ5, feed 0.07 mm/rev, 15 mm deep blind hole, dry), the cutting speed equivalent to a tool life of 1000 mm is 23 m/min for SUS303 (SUS304: 14, C3604: >300)[13]
📚Sources
Primary sources (public documents from makers, industry associations and standards bodies), numbered where each value is cited. Many are in Japanese.
- jssa.gr.jp https://www.jssa.gr.jp/contents/products/standards/jis/austenite/
- nipponsteel.com https://www.nipponsteel.com/product/catalog_download/__icsFiles/afieldfile/2025/10/06/S011…
- sandvik.coromant.com https://www.sandvik.coromant.com/en-us/knowledge/materials/workpiece-materials
- kyocera.co.jp https://www.kyocera.co.jp/prdct/tool/wp-content/uploads/2014/07/2024-2026_A.pdf
- sumitool.com https://www.sumitool.com/downloads/cutting-tools/general-catalog/assets/pdf/a.pdf
- sanyo-steel.co.jp https://www.sanyo-steel.co.jp/english/product/special_steel/images/pdf/stainless_201712.pd…
- aichi-steel.co.jp https://www.aichi-steel.co.jp/_assets/dl/products/stainless_company/stainless_catalog.pdf
- swisssteel-group.com https://swisssteel-group.com/content-media/documents/Data-Sheets/Stainless-Steel/1.4305_de…
- jssa.gr.jp https://www.jssa.gr.jp/contents/products/standards/comparisons/
- swisssteel-group.com https://swisssteel-group.com/content-media/documents/_import/DAT-UGIMA-X-4305-en.pdf
- kyocera.co.jp https://www.kyocera.co.jp/prdct/tool/wp-content/uploads/2016/06/R_2016.pdf
- jssa.gr.jp https://www.jssa.gr.jp/contents/about_stainless/selections/performances/
- daido.co.jp https://www.daido.co.jp/products/stainless/starcut13cr/starcut13cr.pdf
Other materials
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