303 Stainless Steel
303 stainless steel is an austenitic Cr–Ni grade designed for fast machining. It is often selected for high-volume parts where cutting speed, tool life, and stable dimensions matter.
- CNC turning parts and precision fittings
- Shafts, sleeves, bushings, couplings, inserts
- Screws, nuts, and small mechanical components
- Projects that need clean machining and reliable supply
- Marine or chloride-rich environments
- Severe forming and deep drawing
- Welding-heavy assemblies
- Strong acids and aggressive chemical service
303 is commonly specified for machining productivity. The main reason is sulfur addition, which helps chip breaking. This improves cutting, drilling, and turning efficiency. It also helps reduce tool wear in many production lines.
The trade-off is practical: 303 is not the first choice for severe forming or welding-heavy projects. If corrosion performance is critical, buyers often evaluate 304 or 316L depending on the service environment.
| Standard system | Designation |
|---|---|
| ASTM / AISI | 303 |
| UNS | S30300 |
| JIS | SUS303 |
| EN | 1.4305 |
| DIN name | X10CrNiS18-9 |
| GOST | 12Х18Н10С |
Typical ranges are shown for reference. Confirm your required limits in the contract and MTC.
| Grade | Reference | C | Cr | Ni | Mn | Si | P | S | N | Fe |
|---|---|---|---|---|---|---|---|---|---|---|
| 303 / S30300 | Typical industry spec | ≤0.15 | 17.0–19.0 | 8.0–10.0 | ≤2.0 | ≤1.0 | ≤0.20 | 0.15–0.35 | ≤0.10 | Balance |
| 1.4305 | EN typical | ≤0.10 | 17.0–19.0 | 8.0–10.0 | ≤2.0 | ≤0.10 | ≤0.05 | 0.15–0.35 | — | Balance |
| SUS303 | JIS typical | ≤0.15 | 17.0–19.0 | 8.0–10.0 | ≤2.0 | ≤1.0 | ≤0.20 | 0.15–0.35 | — | Balance |
| Grade | Condition | Tensile strength | Yield strength | Elongation | Hardness |
|---|---|---|---|---|---|
| AISI 303 | Annealed | ≥ 520 MPa | ≥ 205 MPa | ≥ 40% | ≤ 230 HB |
| 1.4305 | Annealed | ≥ 500 MPa | ≥ 190 MPa | ≥ 35% | ≤ 230 HB |
| SUS303 | Annealed | ≥ 520 MPa | ≥ 205 MPa | ≥ 40% | ≤ 230 HB |
For machining projects, define target hardness and inspection method in the RFQ. Use the Hardness Conversion page if your team uses different scales.
- High machinability: often reported as up to 50% faster machining than 304 in suitable setups.
- Stable cutting: good chip breaking and reliable dimensional control during machining.
- Good surface finish: suitable for precision parts and clean appearance needs.
- Corrosion resistance: good in mild environments such as fresh water and typical atmospheric exposure.
- Practical limitation: avoid marine exposure, severe forming, and welding-heavy assemblies.
303 performs well in mild environments. For aggressive media, align grade selection with the service condition.
303 is commonly used on CNC lathes and automatic screw machines. It supports smooth cutting and reduces built-up edge in many cases.
303 has reduced ductility compared with 304. Deep drawing is usually not recommended for this grade.
303 is not recommended for welding-heavy assemblies due to sulfur. If welding is required, many buyers select 304 or 304L instead.
303 is widely purchased in bars, rods, and tubes for machining, and it is also available in sheet, plate, coil, and strip for general use. Share your target standard, size, finish, and quantity for a workable offer.
Thickness: 0.3–6.0 mm
Thickness: 3–100 mm
Thickness: 0.3–6.0 mm
Thickness: 3–14 mm
Thickness: 0.3–10 mm
WT: 1–100 mm
WT: 1–100 mm
Length: 100–12000 mm
Thickness: 3–60 mm
| Item | 303 | 304 | 316L |
|---|---|---|---|
| Main advantage | Machining productivity | Balanced general performance | Stronger chloride resistance |
| Machinability | Excellent | Moderate | Moderate |
| Welding suitability | Not preferred | Good | Good |
| Forming / deep drawing | Not preferred | Good | Good |
| Marine / chloride service | Not recommended | Limited | Common choice |
| Typical use | Precision machined parts | General fabrication | Marine / chemical environments |
Is 303 magnetic?
In the annealed condition it is generally non-magnetic. After cold working, it may become slightly magnetic.
Can 303 replace 304?
For machining-focused parts, 303 is often acceptable. For welding-heavy assemblies or higher corrosion needs, 304 or 316L is usually a better choice.
Is 303 suitable for marine environments?
It is not recommended for chloride-rich exposure. For marine service, 316L is commonly selected.
Can 303 be polished?
It can reach a good finish. If a mirror-like appearance is critical, many buyers evaluate 304 for easier polishing performance.
Send your target grade, size, quantity, finish, and destination port. We will respond with an offer and practical lead time.
