4340 Alloy Steel
Versatile alloy steel used in aerospace, automotive, and oil and gas industries for high strength, toughness, and wear resistance. Excellent hardenability and fatigue strength.
Chemical Composition
| Element | Percentage (% by weight) |
|---|---|
| Fe | 95.195 - 96.33 (balance) |
| Ni | 1.65 - 2 |
| Cr | 0.7 - 0.9 |
| Mn | 0.6 - 0.8 |
| C | 0.37 - 0.43 |
| Mo | 0.2 - 0.3 |
| Si | 0.15 - 0.3 |
| S | max 0.04 |
| P | max 0.035 |
Physical Properties
- Density (kg/m³)
- 7850
- Melting point (°C)
- 1427
Mechanical Properties
- Tensile strength (MPa)
- 745
- Yield strength (MPa)
- 470
- Hardness (HB)
- 217
- Elongation (%)
- 22
- Note
- annealed condition
Thermal Properties
- Thermal conductivity (W/m·K)
- 44.5
Typical Applications
- Gears
- Crankshafts
- Aircraft landing gear
- High-stress shafts
Buying This Grade in Pakistan
Used by the same forging and gear-manufacturing shops that buy 4140, chosen over it specifically where higher core toughness is needed, aircraft-grade landing gear and heavy-duty crankshafts are the textbook use, though most Pakistani demand is automotive and general machinery shafts.
Related reading
- Sourcing steel for auto parts forging: a PAAPAM supplier's grade checklist
A practical grade-selection checklist for Pakistani auto parts forging shops, built around what PAAPAM-member companies actually forge and heat treat.
- 4140 alloy steel: the forging industry's workhorse, explained
Why 4140 shows up in nearly every Pakistani auto parts forging shop, and what its composition actually gives you.
Grade Family
Nickel-chromium-molybdenum low alloy steel
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