430 / 430F Stainless Steel
430 is a ferritic chromium (16–18%) stainless steel, non-hardenable by heat treatment, which combines:
- Good corrosion resistance (especially against organic acids and nitric acid).
- Excellent formability.
- Fair mechanical properties.
The 430F variant is a free-machining version of 430, with higher sulfur content to improve machinability on automatic machines. It is mainly supplied in bar form.
Chemical composition (%)
| Grade | C | Mn | Si | P | S | Cr | Mo |
| 430 | ≤0.12 | ≤1.00 | ≤1.00 | ≤0.040 | ≤0.030 | 16.0–18.0 | ≤0.75 |
| 430F | ≤0.12 | ≤1.25 | ≤1.00 | ≤0.06 | ≥0.15 | 16.0–18.0 | – |
Mechanical properties
| Grade | Tensile strength (MPa) | Yield strength (0.2%) (MPa) | Elongation (%) | Hardness HRB | Hardness HB |
| 430 | ≥450 | ≥205 | ≥22 | ≤89 | ≤183 |
| 430F (typical) | 552 | 379 | 25 | – | 262 |
Physical properties (annealed condition)
| Property | Value |
| Density | 7700 kg/m³ |
| Modulus of elasticity | 200 GPa |
| Coefficient of thermal expansion (0–538°C) | 11.4 µm/m·°C |
| Thermal conductivity (at 100°C) | 23.9 W/m·K |
| Thermal conductivity (at 500°C) | 26.0 W/m·K |
| Specific heat | 460 J/kg·K |
| Electrical resistivity | 600 nΩ·m |
Corrosion resistance
- Good in moderate indoor environments.
- Limited pitting resistance compared to 304 and 316.
- Maximum performance achievable with polished or bright surfaces.
- Not recommended for prolonged outdoor exposure without protection.
Heat resistance
- Oxidation:
- Up to 870°C in intermittent service.
- Up to 815°C in continuous service.
- Embrittlement:
- Possible after prolonged exposure to 400–600°C; can be eliminated by annealing.
Heat treatments
- Solution annealing: 815–845°C, slow furnace cooling to 600°C, then rapid air cooling.
- Subcritical annealing: 760–815°C, air or water cooling.
- Non-hardenable by heat treatment.
Weldability
- Pre-heating to 150–200°C.
- Post-heating at 790–815°C to reduce embrittlement.
- Use of fillers type 430, 308L, 309, or 310 depending on the application.
Machinability
- 430: Easier to machine than austenitic grades, but with a risk of galling.
- 430F: Highly machinable, specific for high-speed automatic machining.
Industrial applications
- Appliances: Dishwasher linings, refrigerator panels.
- Automotive: Decorative trim, interior finishes.
- Chemical industry: Equipment in contact with dilute nitric acid.
- Kitchen appliances: Stove rings, heating element supports.
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