AISI 4140 Steel (UNS G41400)
Description
AISI 4140 alloy steel is a medium carbon, chromium-molybdenum, through-hardening alloy steel that has a good hardenability with high strength and toughness as well as good fatigue and impact resistance after heat treating. It can be readily nitrided for improved surface wear. For best machining, it is often used in the annealed condition; however, when the amount of machining necessary is minimal or when the risk of distortion in heat treating a finished part is paramount, it is typically used in the quenched and tempered condition. Typical applications for 4140 bar are sprockets, bolts, chain pins, drill collars, universal joints, highly stressed parts or parts subject to severe wear.
Chemical Composition
Chemical Composition (wt%) limits of AISI 4140 per ASTM A29*
| Carbon | 0.38-0.43 | Molybdenum | 0.15-0.25 |
| Manganese | 0.75-1.00 | Phosphorus | 0.035 |
| Silicon | 0.15-0.35 | Sulfur | 0.040 |
| Chromium | 0.80-1.10 |
*Maximum, unless range is indicated
Physical Properties
Physical properties for AISI 4140 Steel
| Density, lb/in3 | 0.284 |
| Modulus of Elasticity, psi | 29 x 106 |
| Coefficient of Thermal Expansion, 68-212˚F, /˚F | 6.83 x 10-6 |
| Thermal Conductivity, Btu/ft hr ˚F | 30.0 |
| Specific Heat, Btu/lb ˚F | 0.114 |
| Electrical Resistivity, Microhm-in | 6.42 |
Standards
Typical standards for AISI 4140 Steel
| ASTM A29 |
| ASTM A322 |