303 vs 630 / 17-4PH: 43% composition overlap. Significantly different materials serving different application areas.
303 vs 630 / 17-4PH
Side-by-side chemical composition and mechanical property comparison.
Overview
303
1.4305
Free-machining austenitic stainless steel — the most machinable of all austenitic grades. 0.15-0.35% S (as MnS inclusions) provides excellent chip-breaking. Trade-off: lower corrosion resistance than 304, poor weldability (hot cracking risk), and not suitable for cold forming. Used for high-volume automatic lathe parts: fittings, valves, screws, shafts, and precision components.
630 / 17-4PH
1.4542
Precipitation-hardening martensitic stainless steel — the highest-strength stainless in common use. Solution anneal at 1040°C then age at 480-620°C for UTS >1300 MPa. Corrosion resistance similar to 304. Cu+Nb precipitation hardening. Trade names include 17-4PH, SUS630. Used for aerospace structural parts, turbine blades, valve components, nuclear waste casks, medical instruments, and oil/gas equipment.
| 303 | 630 / 17-4PH | |
|---|---|---|
| Material Number | 1.4305 | 1.4542 |
| Category | Stainless Steel | Stainless Steel |
| Standard | EN 10088-3 | EN 10088-3 |
Chemical composition (wt%)
| Element | 303 | 630 / 17-4PH | Overlap |
|---|---|---|---|
| C | 0–0.1% | 0–0.07% | OK |
| Si | 0–1% | 0–0.7% | OK |
| Mn | 0–2% | 0–1.5% | OK |
| P | 0–0.045% | 0–0.04% | OK |
Mechanical properties
| Property | 303 | 630 / 17-4PH | Unit |
|---|---|---|---|
| tensile_strength | 500–750 | ≥ 1310 | MPa |
| yield_strength | ≥ 190 | ≥ 1170 | MPa |
| elongation | ≥ 35 | ≥ 10 | % |
Compatibility Assessment
303 and 630 / 17-4PH have significantly different compositions (43% overlap). These materials are not interchangeable and serve different application areas.
Automated assessment based on composition analysis
Frequently Asked Questions
Is 303 the same as 630 / 17-4PH?
303 and 630 / 17-4PH have a 43% composition overlap. They are generally not directly interchangeable.
Can I replace 303 with 630 / 17-4PH?
Generally not recommended. The compositions differ significantly (43% overlap). These materials have different alloying concepts and are intended for different applications.
What is the difference between 303 and 630 / 17-4PH?
The main differences are in the following elements: S, Cr, Ni. 303 is a Stainless Steel grade, while 630 / 17-4PH is a Stainless Steel grade.
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Data provided for reference only. Always verify against the applicable specification for critical applications.
All data is for reference only. Equivalents indicate similarity, not identity. Always verify against the applicable specification for safety-critical applications. materialref.com accepts no liability for decisions based on this data.