Peeled Round Bars / Alloy Steel
AISI 4140
Chromium-Molybdenum Alloy Steel
Material Overview
AISI 4140 - Chromium-Molybdenum Alloy Steel
Material Type
Alloy Elements: Chromium (0.8-1.1%), Molybdenum (0.15-0.25%)
Key Benefit: Very high tensile and yield strength with excellent toughness
Key Properties
- Strength: Very high tensile and yield strength
- Impact Resistance: Excellent toughness under dynamic loads
- Wear Resistance: High due to Cr-Mo combination
- Hardenability: Through-hardening capability
Mechanical Properties
| Tensile Strength: | 700-1200 MPa (depending on HT) |
| Yield Strength: | 415-1100 MPa |
| Hardness (Heat Treated): | Up to 50-55 HRC |
| Impact Strength: | High (Charpy V-notch) |
Heat Treatment Behavior
- Oil Quenching: Can be oil-quenched for uniform hardening
- Through-Hardening: Hardens throughout the section
- Tempering Response: Excellent tempering characteristics
- Dimensional Stability: Minimal distortion during heat treatment
Applications
- High-load shafts and axles
- Machine tool spindles
- Connecting rods and crankshafts
- Drill collars and tool holders
- Gear components (high strength)
- Hydraulic cylinder rods
- Aerospace and automotive components
Advantages
- Superior Strength: Much higher than carbon steels
- Excellent Toughness: Resists shock and impact loading
- Wear Resistance: High hardness with good toughness
- Fatigue Strength: Excellent for cyclic loading
- Versatility: Wide range of applications
Heat Treatment
- Normalizing: 870-900°C, air cool
- Hardening: 830-860°C, oil quench
- Tempering: 205-650°C (depending on desired hardness)
- Annealing: 815-845°C, furnace cool
Processing Characteristics
- Machining: Good in annealed condition
- Welding: Fair - requires pre-heat and post-weld heat treatment
- Forming: Good in annealed condition
- Grinding: Excellent after heat treatment