304 stainless steel provides corrosion resistance without coatings, ideal for food, medical, and chemical environments. 4140 alloy steel offers higher strength and hardenability at lower cost for industrial machinery where coatings are acceptable.
| Property | Stainless Steel 304 | Alloy Steel 4140 |
|---|---|---|
| Tensile Strength | 515 MPa (75 ksi) | 655 MPa (95 ksi) |
| Yield Strength | 205 MPa (30 ksi) | 415 MPa (60 ksi) |
| Hardness | 201 HB | 197 HB |
| Density | 8.00 g/cm³ | 7.85 g/cm³ |
| Machinability Rating | 45/100 | 66/100 |
| Thermal Conductivity | 16.2 W/m·K | 42.6 W/m·K |
| Melting Point | 1,400–1,450 °C | 1,416–1,460 °C |
| Tolerance | ±0.01 mm | ±0.01 mm |
| Property | Stainless Steel 304 | Alloy Steel 4140 | Winner |
|---|---|---|---|
| Corrosion Resistance | Excellent (no coating) | Poor (needs coating) | Stainless |
| Tensile Strength | 515 MPa | 655 MPa | Alloy |
| Machinability | 45/100 | 66/100 | Alloy |
| Through-Hardenable | No | Yes | Alloy |
| Material Cost | ~$2.50/lb | ~$1.00/lb | Alloy |
| Maintenance Cost | Low (no rust) | Higher (coating needed) | Stainless |
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