Alloy Steel 4340
Alloy Steel 4340 is a nickel-chromium-molybdenum alloy steel known for its exceptional toughness and high fatigue strength. It is the premium choice for aerospace and defense applications requiring maximum strength and reliability.
Machinability
57/100
Tolerance
±0.02 mm
Category
Carbon & Alloy Steel
Material Properties
| Property | Value |
|---|---|
| Tensile Strength | 745 MPa (108 ksi) |
| Yield Strength | 470 MPa (68 ksi) |
| Hardness | 217 HB |
| Density | 7.85 g/cm³ |
| Machinability Rating | 57/100 |
| Thermal Conductivity | 44.5 W/m·K |
| Melting Point | 1,427–1,477 °C |
| Tolerance | ±0.02 mm |
Common Grades
4340 Annealed4340 Normalized4340 Q&T
Advantages
- Exceptional toughness
- Very high fatigue strength
- Deep hardenability
- Excellent impact resistance
Limitations
- Difficult to machine when hardened
- Poor corrosion resistance
- Expensive
Common Applications
Landing gear
Power transmission gears
Crankshafts
Heavy-duty shafts
Structural fasteners
Industries Served
AerospaceDefenseOil & GasAutomotive
Available Surface Finishes
Black OxideHard ChromeCadmium PlatingNitride