17-4 PH Stainless vs 304 Stainless
17-4 PH and 304 sit at opposite ends of the stainless spectrum. 17-4 PH is a precipitation-hardening martensitic grade that heat-treats to very high strength, while 304 is the default soft austenitic grade prized for corrosion resistance and formability. Engineers weigh them when deciding whether a part needs structural strength or maximum corrosion resistance and formability.
The verdict
Choose 17-4 PH for high-strength, high-hardness stainless parts — it ages to ~1000 MPa yield and 38 HRC, far beyond 304's 215 MPa yield. Choose 304 when corrosion resistance, ductility and easy forming/welding matter most — 304's austenitic 18/8 structure forms readily (40% elongation), welds cleanly and resists corrosion better, but offers only modest strength.
Side-by-side data
| Property | 17-4 PH Stainless | 304 Stainless |
|---|---|---|
| Category | Stainless Steel | Stainless Steel |
| Density (g/cm³) | 7.8 | 8.0 |
| Tensile strength (MPa) | 1070 | 515 |
| Yield strength (MPa) | 1000 | 215 |
| Elongation (%) | 10 | 40 |
| Hardness | 38 HRC | 201 HB |
| Max service temp (°C) | 300 | 870 |
| Machinability | ●●●●● | ●●●●● |
| Corrosion resistance | ●●●●● | ●●●●● |
| Relative cost | ●●●●● | ●●●●● |
| Thermal cond. (W/m·K) | 18 | 16 |
| Typically used for | High-strength corrosion-resistant parts | General corrosion-resistant parts |
Which should you choose?
Choose 17-4 PH Stainless when…
- The part is a highly-stressed shaft, fastener, gear or valve needing ~1000 MPa yield
- High hardness (38 HRC) and wear/fatigue resistance are required in a stainless part
- A simple low-temperature aging step must set properties with minimal distortion
- Strength-to-section ratio is critical and weight/size must stay compact
- Moderate service temperature is acceptable (rated ~300°C)
- You can accept harder machining and a magnetic, martensitic structure
Choose 304 Stainless when…
- Corrosion resistance and a clean, hygienic surface are the priority
- The part is deep-formed, drawn or rolled (40% elongation)
- Easy, reliable welding is required
- A non-magnetic stainless is needed
- Cost matters — 304 is cheaper and far more widely stocked
- High service temperature up to ~870°C is required
Key differences that matter
- 17-4 PH is precipitation-hardening martensitic; 304 is austenitic 18/8 — opposite families
- 17-4 PH is vastly stronger: ~1000 MPa yield / 1070 MPa tensile at 38 HRC vs 304's 215 MPa yield
- 304 has higher corrosion resistance and is more ductile (40% vs 10% elongation)
- 304 welds and forms easily; 17-4 forms poorly and needs care when welded
- 17-4 is magnetic (martensitic); 304 is essentially non-magnetic
- 17-4 hardens by a simple aging treatment with little distortion; 304 cannot be heat-hardened
- 304 is cheaper and serves to ~870°C; 17-4 is pricier and rated to ~300°C
Need 17-4 PH Stainless or 304 Stainless parts made?
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Open the Material SelectorGet a Quote →Frequently asked questions
Is 17-4 PH stronger than 304?
Yes, dramatically. Aged 17-4 PH reaches roughly 1000 MPa yield and 1070 MPa tensile at 38 HRC, while 304 sits near 215 MPa yield and 515 MPa tensile. 17-4 is chosen specifically when a stainless part must carry high loads; 304 is a corrosion grade, not a strength grade.
Which resists corrosion better?
304. Its austenitic 18/8 chemistry gives a higher corrosion rating than martensitic 17-4 PH, especially in damp, mildly chloride or food-acid environments. 17-4 is corrosion-resistant for a high-strength grade, but it trades some corrosion performance for the strength its martensitic structure provides.
Can 304 be hardened like 17-4 PH?
No. 304 is austenitic and cannot be hardened by heat treatment — it only strengthens through cold work, which still leaves it far softer than 17-4. 17-4 PH is precipitation-hardening: a low-temperature aging step precipitates copper-rich phases to reach high strength and hardness with minimal distortion.
Is 304 easier to weld and form?
Yes, by a wide margin. 304's 40% elongation makes it excellent for deep drawing and bending, and it welds with standard practice. 17-4 PH has only ~10% elongation, forms poorly, and welding it generally requires post-weld heat treatment to restore properties, so 304 is preferred for fabricated, formed parts.
Is 17-4 PH magnetic and 304 not?
Correct. 17-4 PH is martensitic and ferromagnetic, so it sticks to a magnet, while 304 is austenitic and essentially non-magnetic in the annealed state. If a non-magnetic stainless is required, 304 fits and 17-4 PH does not.
Property values are typical/nominal figures for early-stage guidance only and vary by temper, grade, supplier and heat treatment. Confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.