4140 Round Bar: Material Profile
4140 is a common choice for components exposed to heavy loads, impact, and repeated stress.
The chromium-molybdenum composition supports through-hardening and consistent mechanical properties across a wide range of industrial applications.
Purchase to the controlling ASTM, SAE, AMS, or customer specification. Section size, supply condition, mechanical properties, surface limits, testing, and heat/lot traceability can change the acceptable material and processing route.
Key Characteristics
- High strength and toughness
- Good fatigue resistance
- Responsive to heat treatment
- Good abrasion resistance
Common Applications
- Drive shafts and axles
- Gears and couplings
- Tool holders
- Hydraulic cylinder rods and mold bases
Typical Chemical Range
| Element | Weight % |
|---|---|
| Carbon | 0.38–0.43 |
| Manganese | 0.75–1.00 |
| Silicon | 0.15–0.35 |
| Chromium | 0.80–1.10 |
| Molybdenum | 0.15–0.25 |
| Phosphorus (max) | 0.035 |
| Sulfur (max) | 0.040 |
Chemistry ranges are general reference values. The purchase specification and material certification govern the order.
