SAE/AISI 8720 Alloy Steel (UNS G87200)
SAE/AISI 8720 is a low-alloy, case-hardening steel that is used in a variety of applications, including gears, shafts, and camshafts. It has good machinability and strength, and can be heat treated to achieve a wide range of properties.
| Chemical Composition | ||
|---|---|---|
| Element | Min | Max |
| Iron | 96.895% | 97.97% |
| Carbon | 0.18% | 0.23% |
| Chromium | 0.40% | 0.60% |
| Manganese | 0.70% | 0.90% |
| Molybdenum | 0.20% | 0.30% |
| Nickel | 0.40% | 0.70% |
| Phosphorous | 0.035% | |
| Silicon | 0.15% | 0.30% |
| Sulfur | 0.04% | |
The following table provides a list of SAE/AISI 8720 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 |
| Young’s Modulus (E) | 190 - 210 GPa |
| Bulk Modulus (K) | 140 GPa |
| Shear Modulus (G) | 80 GPa |
| Poisson’s Ratio (ν) | 0.27 - 0.30 |
| Brinell Hardness | 179 - 235 |
| Thermal Properties | Metric |
| Thermal Conductivity | 46.6 W/m·K |
| Specific Heat Capacity (Cp) | 470 J/kg·K |
| Coefficient of Thermal Expansion (αL) | 1.1×10-5 1/°C |
| Electrical Properties | Metric |
| Electrical Conductivity | 4.23×106 S/m |
| Electrical Resistivity | 2.36×10-7 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 8720 Alloy Steel
| Advantages | Disadvantages |
|---|---|
| High strength and toughness | Relatively low corrosion resistance |
| Excellent wear resistance | Limited weldability |
| Good hardenability and case depth | Requires careful heat treatment to achieve desired properties |
| Suitable for applications requiring high load-bearing capacity | Susceptible to cracking if not properly heat treated |
| Resistant to fatigue and impact | Higher cost compared to carbon steels |
Applications of 8720 Alloy Steel
AISI 8720 steel, with its combination of high strength, toughness, and wear resistance, finds application in various industries. Here are some common applications of AISI 8720 steel:
- Gears and Gear Shafts: AISI 8720 steel's excellent wear resistance and high load-bearing capacity make it suitable for manufacturing gears and gear shafts used in heavy machinery, automotive transmissions, and power transmission systems.
- Bolts and Fasteners: Due to its high strength and toughness, AISI 8720 steel is often used to produce bolts, screws, and other fasteners for applications that require reliability, resistance to fatigue, and the ability to withstand high stress.
- Bearings: The wear resistance and hardness of AISI 8720 steel make it suitable for producing bearings, especially in applications where high load capacities, toughness, and resistance to wear are crucial.
- Axles and Shafts: AISI 8720 steel is utilized in the production of axles and shafts for various industries, including automotive, agriculture, and construction. Its strength, toughness, and resistance to bending and torsion make it suitable for these demanding applications.
- Hydraulic Components: The high strength and fatigue resistance of AISI 8720 steel make it a suitable material for hydraulic components such as pistons, rods, and cylinders.
- Tooling and Dies: AISI 8720 steel is sometimes used in tooling and die manufacturing for applications that require high strength, wear resistance, and toughness, such as in forging dies, die casting molds, and extrusion tooling.
- General Engineering Applications: AISI 8720 steel is employed in various general engineering applications where a combination of strength, toughness, and wear resistance is required. This includes components such as shafts, pins, couplings, and spindles.