4140 Chromium-Molybdenum Alloy Steel
4140 alloy steel delivers exceptional strength (655-1020 MPa tensile) with superior toughness and wear resistance, ideal for high-stress components like gears, axles, and hydraulic systems in automotive, aerospace, and industrial machinery.
Product Summary
4140 Chromoly steel (UNS G41400) is a versatile medium-carbon alloy renowned for its balanced combination of hardness, fatigue resistance, and machinability. Enhanced by chromium (0.80-1.10%) and molybdenum (0.15-0.25%), this heat-treatable steel achieves optimal performance in hardened/tempered conditions, making it indispensable for heavy-duty applications. Compliant with ASTM A29 and SAE J404 standards, it excels in environments demanding dynamic load endurance and dimensional stability.
Key Features
1. Mechanical Excellence
Tensile Strength: 655-1020 MPa (adjustable via heat treatment)
Hardness: 28-32 HRC (quenched & tempered), up to 55 HRC (oil-quenched)
Impact Toughness: 45J at -20°C (Charpy V-notch per ASTM E23)
2. Manufacturing Versatility
Machinability: 65% vs. 1212 steel baseline (improved chip control)
Weldability: Pre-heat to 150-260°C for thickness >25mm (AWS D1.1 compliant)
3. Thermal & Chemical Resilience
Operating Range: -40°C to 425°C (retains 85% yield strength at 300°C)
Corrosion Resistance: 2x lifespan vs. 1045 steel in humid environments
Industrial Applications
| Sector | Critical Components | Performance Advantage |
|---|---|---|
| Automotive | Gear shafts, Crankshafts | 25% higher torsional strength vs. 4340 steel |
| Aerospace | Landing gear actuators | 18% weight reduction with equal load capacity |
| Energy | Drill collars, Valve bodies | NACE MR0175 compliance for H₂S environments |
| Tooling | Die blocks, Molding plates | 30% longer service life under cyclic loads |
Global Standard Grades
North America:
ASTM A29/A29M (Bar stock)
SAE J404 (Automotive spec)
AMS 6381 (Aerospace-grade)
International Equivalents:
EN 1.7225 (Europe)
JIS SCM440 (Japan)
GB 42CrMo (China)
Chemical Composition & Functional Roles
| Element | Content (%) | Technical Purpose |
|---|---|---|
| Carbon (C) | 0.38-0.43 | Core strength & hardenability |
| Chromium (Cr) | 0.80-1.10 | Wear resistance & hardenability |
| Molybdenum (Mo) | 0.15-0.25 | High-temperature stability |
| Manganese (Mn) | 0.75-1.00 | Deoxidizer & forgeability enhancer |
| Silicon (Si) | 0.15-0.35 | Strength & fatigue resistance |
Trace Elements:
Phosphorus (P) ≤0.035%, Sulfur (S) ≤0.040% (controlled for weldability)
