Primarily made up of chromium and carbon, with smaller amounts of other metals, 440C stainless steel has the highest hardness and is the most heat resistant of all stainless steels. It is a high-carbon martensitic stainless steel known for its excellent mechanical properties and wear resistance, partly due to the trace amounts of other elements like silicon, molybdenum, and manganese.
Due to its hardness, high corrosion resistance, and good high-temperature properties, it is often used to manufacture bearing parts in corrosive environments, cutting tools, razor-sharp edges, cutlery, and nozzles. 440C stainless steel is especially crucial for critical components in the aerospace industry, such as turbine blades, landing gear parts, and aircraft bearings that demand strong, wear, and corrosion-resistant alloys.
| Property | Value | Notes |
|---|---|---|
| Material Type | Martensitic Stainless Steel | UNS S44004 |
| Density | 7.75 g/cm³ | 0.280 lb/in³ |
| Melting Point | ~1,480–1,510°C | ~2,700–2,750°F |
| Hardness (HRC) | 58–65 | Achieved after proper heat treatment |
| Tensile Strength | ~760–1,860 MPa | ~110,000–270,000 psi depending on tempering |
| Yield Strength | ~450–1,600 MPa | ~65,000–230,000 psi |
| Elongation at Break | ~1–5% | Very low ductility |
| Modulus of Elasticity | ~200 GPa | ~29 x 10⁶ psi |
| Corrosion Resistance | Moderate to Good | Lower than austenitic grades; good in mild environments |
| Magnetism | Magnetic | Due to martensitic structure |
| Heat Treatment | Required for Hardening | Hardenable by quenching and tempering |
| Machinability | Poor to Fair | Best when annealed |
| Weldability | Poor | Not recommended unless annealed; post-weld heat treatment is critical |
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