SAE/AISI 4118 Alloy Steel (UNS G41180)
SAE/AISI 4118 alloy steel is a versatile chromium-molybdenum steel widely valued for its strength, toughness, and wear resistance. It is commonly employed in manufacturing gears, shafts, bolts, and various mechanical components requiring durability and performance under stress.
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| Chemical Composition | ||
|---|---|---|
| Element | Min | Max |
| Iron | 97.70% | 98.49% |
| Carbon | 0.18% | 0.23% |
| Chromium | 0.40% | 0.60% |
| Manganese | 0.70% | 0.90% |
| Molybdenum | 0.08% | 0.15% |
| Phosphorous | —— | 0.035% |
| Silicon | 0.15% | 0.35% |
| Sulfur | —— | 0.04% |
The following table provides a list of SAE/AISI 4118 properties in both SI and US customary/Imperial units.
Click on the button to switch between Metric and Imperial units.
| Physical Properties | Metric |
|---|---|
| Density | 7850 kg/m3 |
| Mechanical Properties | Metric |
| Tensile Strength (Ultimate) | 517 MPa |
| Tensile Strength (Yield) | 365 MPa |
| Young’s Modulus (E) | 190 - 210 GPa |
| Bulk Modulus (K) | 140 GPa |
| Shear Modulus (G) | 80 GPa |
| Elongation at Break | 33% |
| Reduction of Area | 64% |
| Poisson’s Ratio (ν) | 0.27 - 0.30 |
| Brinell Hardness | 137 |
| Thermal Properties | Metric |
| Thermal Conductivity | 44.5 W/m·K |
| Specific Heat Capacity (Cp) | 470 J/kg·K |
| Coefficient of Thermal Expansion (αL) | 1.3×10-5 1/°C |
| Electrical Properties | Metric |
| Electrical Conductivity | 4.18×106 S/m |
| Electrical Resistivity | 2.4×10-7 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 4118 Alloy Steel
| Advantages | Disadvantages |
|---|---|
| High strength and toughness | Moderate corrosion resistance |
| Good hardenability and wear resistance | Lower machinability compared to some steels |
| Can be heat treated for desired properties | Limited weldability |
| Cost-effective compared to some specialty steels | Susceptible to surface cracking during heat treatment |
Applications of 4118 Alloy Steel
AISI 4118 steel is widely utilized across industries that demand strength, toughness, and wear resistance, including key applications such as:
- Gears and Gear Shafts: Utilized in manufacturing due to high strength, good hardenability, and wear resistance.
- Bolts and Fasteners: Suitable for bolts, studs, and other fasteners because of its toughness and strength.
- Mechanical Components: Applied in shafts, axles, crankshafts, and connecting rods.
- Automotive Parts: Used for crankshafts, transmission components, and steering system parts owing to excellent mechanical properties.
- Machine Tools and Equipment: Employed in producing spindles, gears, and shafts for machine tools.
- Construction and Mining Equipment: Manufactured into pins, bushings, and wear-resistant parts for heavy-duty equipment.
- Agricultural Machinery: Used for components like axles, pins, and shafts in farming machinery.