SAE/AISI 4340 Alloy Steel (UNS G43400)
SAE/AISI 4340 is a high-strength, low-alloy steel that is known for its exceptional toughness, strength, and fatigue resistance, making it suitable for a variety of applications, particularly in the aerospace, oil and gas, and automotive industries.
| Chemical Composition | ||
|---|---|---|
| Element | Min | Max |
| Iron | 95.195% | 96.33% |
| Carbon | 0.37% | 0.43% |
| Chromium | 0.70% | 0.90% |
| Manganese | 0.60% | 0.80% |
| Molybdenum | 0.20% | 0.30% |
| Nickel | 1.65% | 2.0% |
| Phosphorous | 0.035% | |
| Silicon | 0.15% | 0.30% |
| Sulfur | 0.04% | |
The following table provides a list of SAE/AISI 4340 properties in both SI and US customary/Imperial units.
Click on the icon to switch between Metric and Imperial units.
| Physical Properties | Metric |
|---|---|
| Density | 7850 kg/m3 |
| Mechanical Properties | Metric |
| Tensile Strength (Ultimate) | 745 MPa |
| Tensile Strength (Yield) | 470 MPa |
| Young’s Modulus (E) | 190 - 210 GPa |
| Bulk Modulus (K) | 140 GPa |
| Shear Modulus (G) | 80 GPa |
| Elongation at Break | 22% |
| Reduction of Area | 50% |
| Poisson’s Ratio (ν) | 0.27 - 0.30 |
| Brinell Hardness | 217 |
| Thermal Properties | Metric |
| Thermal Conductivity | 44.5 W/m·K |
| Specific Heat Capacity (Cp) | 470 J/kg·K |
| Coefficient of Thermal Expansion (αL) | 1.23×10-5 1/°C |
| Electrical Properties | Metric |
| Electrical Conductivity | 4.35×106 S/m |
| Electrical Resistivity | 2.3×10-7 Ω·m |
The values in this table are approximate and can vary depending on various factors such as the specific manufacturing process and heat treatment applied to the alloy.
Advantages & Disadvantages of 4340 Alloy Steel
| Advantages | Disadvantages |
|---|---|
| High strength and toughness | Relatively high cost |
| Excellent fatigue resistance | Requires careful heat treatment |
| Good wear resistance | Moderate weldability |
| High hardenability and heat treatability | Susceptible to surface corrosion |
| Versatile application range | Lower machinability compared to some steels |
| Good impact resistance |
Applications of 4340 Alloy Steel
AISI 4340 steel finds application in various industries due to its exceptional strength, toughness, and heat treatability. Some common applications of 4340 steel include:
- Aerospace: Components in aircraft and aerospace industry such as landing gear components, engine parts, structural parts, and gears.
- Automotive: Critical components in high-performance automobiles and racing vehicles, including crankshafts, connecting rods, gears, and axle shafts.
- Oil and Gas: Drill collars, mud motor components, shafts, gears, and other heavy-duty equipment used in drilling, exploration, and extraction operations.
- Power Generation: Turbine shafts, generator components, and other parts subjected to high temperatures, high loads, and cyclic stress in power plants.
- Marine: Shafts, propeller components, and other critical parts in marine applications that require high strength, toughness, and resistance to corrosion.
- Tool and Die Making: Tooling components such as punches, dies, and mold inserts that require high strength, wear resistance, and toughness.
- Heavy Machinery: Components in heavy machinery, such as gears, shafts, and structural parts that need to withstand heavy loads and demanding operating conditions.
- Defense and Military: Various components in military vehicles, weapons systems, and aircraft, including gears, shafts, and structural parts.
- Mining and Construction: Components used in mining equipment, construction machinery, and earth-moving equipment that require high strength, durability, and resistance to wear.
- General Engineering: 4340 steel is also used in various general engineering applications, such as crankshafts, gears, spindles, and other high-strength components.