MATERIALS · STAINLESS STEEL
AISI 303 / 1.4305. SS303 is an 18/8 chromium-nickel austenitic stainless steel with 0.15–0.35% sulphur added so that chips break short. It is the easiest austenitic stainless grade to machine, and shops use it for high-volume turned parts such as fasteners, bushes, shafts and fittings. The trade-off is lower corrosion resistance than 304, poor weldability and limited cold formability.
DENSITY
8 g/cm³HARDNESS
230 HB maxTENSILE STRENGTH
500–750 MPaMACHINABILITY
Very good (70%)TURNING, CARBIDE
130–210 m/minCALCULATOR
Enter your part size and your own rates. Density and a starting cutting speed are filled in for this material.
EQUIVALENT GRADES
Nearest equivalents across standards. Check the exact standard on critical parts.
| Standard | Grade |
|---|---|
| AISI/SAE | 303 |
| UNS | S30300 |
| EN / W.Nr | X8CrNiS18-9 / 1.4305 |
| IS | X10Cr18Ni9S (IS 6603:2024) |
| JIS | SUS303 |
| BS | 303S31 (En58M) |
Also known as: 303, 1.4305, X8CrNiS18-9, SUS303, 303S31, En58M, free-machining 18/8
CHEMICAL COMPOSITION
| Element | Weight % |
|---|---|
| C | ≤0.10 |
| Si | ≤1.00 |
| Mn | ≤2.00 |
| P | ≤0.045 (EN 10088-3); ≤0.20 (ASTM) |
| S | 0.15–0.35 (EN 10088-3); ≥0.15 (ASTM) |
| Cr | 17.0–19.0 |
| Ni | 8.0–10.0 |
| Cu | ≤1.00 |
| N | ≤0.10 |
MECHANICAL PROPERTIES
| Condition | Solution annealed bar, EN 10088-3 (up to 160 mm) |
| Tensile strength (MPa) | 500–750 |
| Yield strength (MPa) | 190 min |
| Elongation (%) | 35 min |
| Hardness | 230 HB max |
| Density (g/cm³) | 8 |
MACHINING
| Turning, carbide (m/min) | 130–210 |
| Turning, HSS (m/min) | 30–45 |
| Machinability | Very good, 70% (AISI B1112 = 100% (published figures 69–78%)) |
The sulphur in 303 makes chips break short, which is why it runs well on automatic and sliding-head lathes. It still work-hardens like other austenitic grades, so keep edges sharp, never let the tool dwell or rub, and take a depth of cut that gets under the previous pass. Use positive-rake inserts with a chip breaker and plenty of coolant, because the low thermal conductivity concentrates heat at the cutting edge. Carbide speeds can usually start 20–30% higher than for 304. Do not choose 303 for parts that will later be welded or sharply bent.
APPLICATIONS
INDUSTRIES THAT USE IT
PROCESSING
| Heat treatment | Cannot be hardened by heat treatment; it gains strength only through cold work. Solution anneal at 1010–1120 °C and cool rapidly. |
| Welding | Poor because of the sulphur addition; if welding cannot be avoided, use 308L or 309 filler and anneal afterwards for best corrosion resistance. |
| Supplied as | Round bar, Hex bar, Bright bar, Wire rod |
QUESTIONS
303 is essentially 304 with 0.15–0.35% sulphur added, which makes it the most machinable austenitic stainless steel. The sulphur lowers corrosion resistance, toughness, weldability and cold formability, so 304 is the better choice for welded, bent or corrosion-critical parts.
Welding 303 is not recommended because the sulphur gives it poor weldability. If a weld cannot be avoided, use 308L or 309 filler and anneal afterwards for best corrosion resistance; for welded assemblies, choose 304 or 304L instead.
No. The sulphur-bearing inclusions act as starting points for pitting, so 303 is not suitable for marine environments and is prone to pitting and crevice corrosion in chloride solutions above about 60 °C. It performs well in mild, dry or indoor service.
RELATED MATERIALS
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AISI 304 / 1.4301 · 8 g/cm³
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AISI 316 / 316L / 1.4401 / 1.4404 · 8 g/cm³
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AISI 410 / 1.4006 · 7.75 g/cm³
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AISI 630 (17-4 PH) / 1.4542 · 7.75 g/cm³
Data reviewed 2026-10-02 against:
Typical values for reference. Always check the mill certificate and the standard your customer specifies.
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