303 stainless steel equivalents
303 stainless steel is nearest to EN 1.4305 (X8CrNiS18-9), JIS SUS303 and China GB Y12Cr18Ni9. These are nearest equivalents, not identical grades: the governing standard or mill certificate decides.
- AISI / ASTM / SAE US
- 303
- EN steel number EN 10027-2
- 1.4305
- EN steel name EN 10027-1
- X8CrNiS18-9
- JIS Japan
- SUS303
- GB China
- Y12Cr18Ni9
- Family
- Austenitic stainless, free-machining
About 303
Austenitic stainless, free-machining. General characteristics; check the standard and the supplier for anything critical.
What it is
A free-machining austenitic stainless steel. Added sulphur forms inclusions that break the chip, making it the easiest austenitic grade to machine. The trade-off is lower corrosion resistance than 304 and poor weldability.
Typical uses
Screw-machine and CNC lathe parts, shafts, bushings, fittings, nuts and bolts, and valve parts where welding is not needed.
Machining notes
The best choice of the austenitic grades for high-volume turning. Chips break more easily, but it still work-hardens, so do not let the tool rub.
Related grades
Grades people often compare with this one.
Fasteners and tapping
Stainless fasteners
Stainless bolts are graded to ISO 3506 (for example A2 and A4 austenitic), not to the ISO 898-1 classes in the bolt torque chart. Do not use those torque values for stainless fasteners; stainless threads also gall easily, so use an anti-seize and the fastener maker's figures.
Bolt torque chartTapping stainless
Stainless work-hardens and grips the tap. Aim for about 60–70 % thread: one size larger than the usual tap drill is common. The tap drill chart shows the percentage each drill leaves.
Tap drill chartAll stainless steel grades
Nearest equivalents across the five designation systems.
| AISI / ASTM | EN name | EN number | JIS | China GB |
|---|---|---|---|---|
| 304 | X5CrNi18-10 | 1.4301 | SUS304 | 06Cr19Ni10 |
| 304L | X2CrNi18-9 | 1.4307 | SUS304L | 022Cr19Ni10 |
| 316 | X5CrNiMo17-12-2 | 1.4401 | SUS316 | 06Cr17Ni12Mo2 |
| 316L | X2CrNiMo17-12-2 | 1.4404 | SUS316L | 022Cr17Ni12Mo2 |
| 321 | X6CrNiTi18-10 | 1.4541 | SUS321 | 06Cr18Ni11Ti |
| 303 | X8CrNiS18-9 | 1.4305 | SUS303 | Y12Cr18Ni9 |
| 310S | X8CrNi25-21 | 1.4845 | SUS310S | 06Cr25Ni20 |
| 201 | X12CrMnNiN17-7-5 | 1.4372 | SUS201 | 12Cr17Mn6Ni5N |
| 430 | X6Cr17 | 1.4016 | SUS430 | 10Cr17 |
| 410 | X12Cr13 | 1.4006 | SUS410 | 12Cr13 |
| 420 | X20Cr13 | 1.4021 | SUS420J1 | 20Cr13 |
| 440C | X105CrMo17 | 1.4125 | SUS440C | 108Cr17 |
| 17-4PH (630) | X5CrNiCuNb16-4 | 1.4542 | SUS630 | 05Cr17Ni4Cu4Nb |
| 2205 duplex | X2CrNiMoN22-5-3 | 1.4462 | SUS329J3L | 022Cr23Ni5Mo3N |
Common questions
What is the European equivalent of 303 stainless steel?
The nearest EN grade is 1.4305, steel name X8CrNiS18-9.
What is the JIS equivalent of 303 stainless steel?
The nearest Japanese grade is SUS303.
What is the Chinese GB equivalent of 303 stainless steel?
The nearest Chinese GB grade is Y12Cr18Ni9.
Is 1.4305 the same as 303?
1.4305 (X8CrNiS18-9) is the nearest European equivalent of 303, not an identical grade. Composition limits and required properties differ in detail, so check the governing standard or the mill certificate when it matters.
What is 303 used for?
Screw-machine and CNC lathe parts, shafts, bushings, fittings, nuts and bolts, and valve parts where welding is not needed.