Stainless Grade Comparison: 303 vs 304 vs 316L vs 17-4PH vs 440C
Typical values for the stainless grades we machine weekly. Machinability is rated against B1112 free-machining steel = 100 percent.
| Property | 303 | 304 | 316L | 17-4PH (H900) | 440C (hardened) |
|---|---|---|---|---|---|
| Chinese GB (GB/T 20878) | Y12Cr18Ni9 | 06Cr19Ni10 | 022Cr17Ni12Mo2 | 05Cr17Ni4Cu4Nb | 11Cr17 |
| Tensile (MPa) | approx. 620 | 515 min | 485 min | 1310 | approx. 1970 |
| Yield (MPa) | approx. 240 | 205 min | 170 min | 1170 | approx. 1900 |
| Hardness | HB 160-210 | HB 150-180 | HB 150-180 | HRC 40-44 | HRC 58-60 |
| Machinability (B1112=100%) | 78% | 45% | 36% | 45-55% by condition | 40-50% annealed |
| Corrosion resistance | Moderate | Good | Best of these | Good | Moderate |
| Weldability | Poor (S added) | Good | Good | Special procedure | Poor |
| Typical use at KGL | Fittings, complex parts | Food and chamber parts | Medical, marine | Shafts, high-load seats | Valve needles, bearings |
Stainless Grade FAQ
303 or 304 for small machined fittings?
303 machines noticeably faster because of the added sulfur, so it is our default for complex small fittings when corrosion demands are mild. 304 welds and forms better and avoids the sulfur inclusions, which matters for food and chamber contact parts.
Can you machine 17-4PH in the hardened condition?
We machine 17-4PH in the solution-treated condition, then age to H1025 through H1150 after roughing, and finish critical faces after aging. Final hardness typically lands HRC 32 to 40 depending on the temper.
Do you passivate 316L parts?
Yes, passivation per ASTM A967 with citric or nitric acid, certificate included. Medical and marine 316L parts ship cleaned and passivated by default.
Not Sure 303 Will Do?
Send the environment and loads; the 24-hour quote includes a grade recommendation.
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