4340 | 1.6511 | SNCM439 | 40CrNiMoA
4340 (1.6565 / 40NiCrMo6) is a nickel-chromium-molybdenum alloy steel offering high tensile strength, excellent toughness, and good hardenability. It provides outstanding fatigue and impact resistance, particularly in the quenched and tempered condition, making it suitable for heavy-duty mechanical components.
Available Form
Round Bar
Custom Diameter & Length
Flat Bar
Custom Thickness, Width & Length
Square Bar
Custom Width & Length
Steel Plate
Custom Thickness, Width & Length
Steel Grade Comparison
| W-Nr | EN | AISI | JIS |
| 1.6565 | 40NiCrMo6 | 4340 | SnCM439 |
Chemical Composition(wt%)
| C | Si | Mn | P | S | Cr | Mo | Ni |
| 0.25~0.35 | 0.20~0.80 | 0.40~0.70 | ≤0.04 | ≤0.045 | 0.70~0.90 | 0.20~0.30 | 1.65~2.00 |
Physical Properties
Densityd: 7.85 g/cm3
Modulus of Elasticity: 210 Gpa
Thermal Conductivity: 44.5 W/(m.k)
| Temperature | 20-100℃ | 2-200℃ | 2-300℃ | 2-400℃ |
| Coefficient of Thermal Expansion（×10-6） | 11.1 | 12.1 | 12.9 | – |
Heat Treatment Process
Hardening: Heat the steel to 815~845°C until the whole section reaches temperature. Then quench in oil or polymer to cool.
Annealing: Heat the steel to 830~860°C, hold it well at temperature, and then let it cool slowly inside the furnace.
Tempering: Must be performed immediately after quenching. Heat the steel uniformly at 455~650°C, hold for at least 2 hours, then cool in still air. (Temper temperature depends on target hardness.)
Application Fields
Used for machine, engine and vehicle components subjected to permanent stress where high strength and toughness are required. Typical structural applications include aircraft landing gear, power transmission assemblies, shafts and other structural parts.
Disclaimer: the information and data presented herein are typical values for reference and are not intended as warranties to readers.
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