AISI SAE 8620 Steel: Properties, Equivalents, and Heat Treatment
Imagine a steel alloy that combines strength, toughness, and versatility, catering to a multitude of industrial applications. AISI SAE 8620…
In the realm of materials science and engineering, AISI 8620 alloy steel stands out as a versatile and highly valued material. Renowned for its robust chemical composition and remarkable mechanical properties, this alloy is a go-to choice for industries ranging from automotive to aerospace. Its unique blend of elements like carbon, chromium, nickel, and molybdenum imparts exceptional strength, toughness, and wear resistance, making it ideal for manufacturing critical components such as gears, shafts, and camshafts. But what truly sets AISI 8620 apart is its adaptability in various heat treatment processes, enhancing its durability and machinability to meet the rigorous demands of modern engineering applications. Whether you’re an automotive engineer seeking a reliable material for high-stress parts, a machinery manufacturer aiming for longevity in agricultural equipment, or a defense industry professional in need of resilient components, AISI 8620 alloy steel offers a balanced solution. Dive into this comprehensive guide to explore its composition, properties, and the myriad ways it can elevate your engineering projects.
The chemical makeup of AISI 8620 steel is key to its strength, durability, and wide range of uses.
AISI 8620 steel contains these elements in the following proportions:
The balanced mix of these elements gives AISI 8620 steel its strength, toughness, wear resistance, and machinability, making it ideal for many industrial uses.
AISI 8620 steel is known for its strength and hardness, which can be greatly improved with different heat treatments.
Depending on heat treatment, AISI 8620 steel has a tensile strength of 545 to 795 MPa, allowing it to withstand significant stress. In its annealed state, AISI 8620 steel has a yield strength of around 415 MPa, which increases with quenching and tempering.
AISI 8620 steel is known for its toughness and wear resistance, making it ideal for high-stress and high-friction parts. Its toughness allows it to absorb energy and deform without breaking, which is crucial for dynamic or impact-loaded applications like gears and shafts. Carburizing increases its surface hardness, enhancing wear resistance for applications such as automotive gears and heavy machinery components.
The elastic modulus (Young’s modulus) of AISI 8620 steel is about 205 GPa, indicating its stiffness and suitability for applications needing minimal deformation under load.
AISI 8620 steel has a thermal conductivity of 46.6 W/m·K, which is important for heat dissipation and thermal cycling applications. Its density is about 7.85 g/cm³ (0.284 lb/in³), balancing strength and weight. The specific heat capacity is around 0.1 Btu/lb/°F (32-212 °F), indicating the heat energy required to raise its temperature by one degree, crucial for thermal performance.
AISI 8620 steel’s strength, hardness, toughness, and wear resistance make it versatile for demanding applications. Heat treatment enhances these properties, meeting the needs of industries like automotive, aerospace, and heavy machinery. Its balanced physical properties, including thermal conductivity and density, support its use in components that face both mechanical and thermal stresses.
AISI 8620 alloy steel is widely utilized in the automotive industry due to its superb balance of toughness, strength, and wear resistance. Its ability to undergo carburizing makes it ideal for components requiring a hard, wear-resistant surface and a tough, ductile core, such as gears and shafts. These parts benefit from the wear resistance and strength provided by the carburized surface, ensuring long-lasting performance in automotive transmissions and drive systems.
AISI 8620 is also used for camshafts and crankshafts, where its combination of strength, wear resistance, and toughness is crucial. These parts endure significant stress and friction, making the steel’s properties ideal for maintaining performance and durability.
In agricultural machinery, AISI 8620 alloy steel is valued for its strength and ability to withstand harsh operating conditions. Its toughness and wear resistance are essential for components that must endure heavy loads and abrasive environments, such as bushings and pins. Agricultural equipment often includes gears and drive components made from AISI 8620, which benefit from the steel’s durability and wear resistance.
AISI 8620 alloy steel finds applications in defense equipment due to its excellent mechanical properties, including high strength, toughness, and wear resistance. The steel’s ability to be precisely machined and its durability make it suitable for critical components such as firearms and ammunition parts. Its strength and hardness ensure that these parts can withstand high pressures and stresses, maintaining reliability and performance.
In military vehicles, AISI 8620 is used for various components, including gears, shafts, and structural parts. The steel’s robustness and wear resistance are essential for withstanding the rigors of military operations.
The high chromium content in AISI 8620 alloy steel enhances its corrosion resistance, making it suitable for marine applications. The steel is used for manufacturing components that require good corrosion resistance, such as shafts, gears, and fasteners in marine environments. Its ability to resist oxidation and corrosion ensures long-term performance and reliability in harsh conditions.
AISI 8620 alloy steel’s versatility extends to general engineering and industrial applications. Its combination of mechanical properties and ease of machining makes it a preferred choice for various components. The steel is suitable for making springs and hand tools, where toughness and strength are crucial. Its properties ensure that these tools can endure repeated use and high stress without failing.
In industrial machinery, AISI 8620 is used for bearings, arbors, and other precision components. The steel’s hardness and wear resistance contribute to the longevity and reliability of these parts, ensuring efficient operation of machinery.
The aerospace industry benefits from AISI 8620 alloy steel’s high strength-to-weight ratio, toughness, and wear resistance. These properties are critical for components that must perform reliably under extreme conditions. The steel is used for manufacturing various aircraft components, including gears, shafts, and structural parts. Its ability to withstand high stresses and resist wear ensures the safety and reliability of aerospace systems.
AISI 8620 is also employed in making engine parts that require precise tolerances and high durability. The steel’s machinability and mechanical properties make it ideal for components subjected to high temperatures and stresses in aircraft engines.
AISI 8620 alloy steel responds well to various heat treatment processes, which greatly enhance its mechanical properties.
Carburizing involves heating the steel in a carbon-rich environment to create a hard, wear-resistant surface while maintaining a tough, ductile core. The typical carburizing temperature ranges from 1650°F to 1750°F (900°C to 950°C), followed by quenching and tempering. This process is ideal for parts subjected to high wear and stress, such as gears, shafts, and camshafts.
Quenching involves heating the steel to a high temperature and then rapidly cooling it in oil or water, increasing its strength and hardness. Tempering follows quenching; the steel is reheated to a lower temperature (250°F to 1300°F or 120°C to 700°C) and then cooled again, which reduces brittleness and balances hardness with toughness. For carburized parts, tempering at around 300°F (150°C) can result in a core strength of approximately 135 ksi and a Rockwell C case hardness of 90.
Normalizing heats the steel above its critical range and then cools it in air. This process achieves a uniform microstructure, relieves internal stresses, and enhances mechanical properties. The normalizing temperature for AISI 8620 is around 1675°F (910°C).
Annealing involves heating the steel to around 1550°F (840°C) and then slowly cooling it to 850°F (455°C) at a rate not exceeding 50°F per hour, followed by air cooling. This process reduces hardness and improves machinability, making the steel easier to work with during subsequent manufacturing processes.
AISI 8620 alloy steel is known for its good machinability, influenced by its chemical composition and heat treatment processes.
Machining is usually done before heat treatment or carburizing to achieve close tolerances, as finish machining after these processes should be minimized to avoid damaging the hardened case. The steel’s low carbon content and the presence of elements like molybdenum contribute to its ease of machining.
The low sulfur content in AISI 8620 helps reduce tool wear, making the manufacturing process more efficient and cost-effective. This property is particularly beneficial for high-volume manufacturing, where tool longevity and consistent performance are critical.
Conventional machining methods can be used before heat treatment. After carburizing, machining is generally limited to grinding to preserve the hardened surface. This ensures that the wear-resistant properties of the carburized layer are maintained, enhancing the durability and performance of the final component.
The combination of effective heat treatment processes and good machinability makes AISI 8620 alloy steel a versatile and high-performing material. Its ability to undergo various heat treatments allows for tailored mechanical properties, while its machinability ensures efficient and precise manufacturing. These characteristics make AISI 8620 ideal for a wide range of industrial applications, including automotive, aerospace, and heavy machinery components.
The corrosion resistance of AISI 8620 alloy steel is due to its chemical composition, which includes chromium, nickel, and molybdenum. These elements enhance the steel’s ability to resist corrosion and oxidation.
AISI 8620 alloy steel can resist oxidation at temperatures up to 650°F (343°C), making it suitable for high-temperature environments. This property ensures that the steel maintains its integrity and performance even under high-heat conditions.
The durability of AISI 8620 alloy steel is a result of its balanced mechanical properties and heat treatment processes. The steel’s ability to undergo carburizing and other heat treatments significantly enhances its surface hardness and core toughness, contributing to its overall durability.
Depending on heat treatment, AISI 8620 can achieve a tensile strength between 545 MPa and 795 MPa, and a yield strength around 415 MPa in its annealed state. This wide range allows for customization based on the specific requirements of the application.
After carburizing and hardening, AISI 8620 can reach a surface hardness of HRC 60-63, providing excellent wear resistance. The core remains tough and ductile, allowing it to absorb impact and resist cracking under stress.
AISI 8620’s corrosion resistance and durability make it suitable for harsh environments like marine and industrial settings. Its high chromium and nickel content ensure longevity in marine applications, while its resistance to chemicals and high temperatures is invaluable in industrial environments.
In summary, AISI 8620 alloy steel’s composition and mechanical properties offer excellent corrosion resistance and durability. These features make it a reliable choice for demanding applications in automotive, aerospace, marine, and industrial sectors, ensuring long-term performance and reliability.
AISI 8620 alloy steel, also known as SAE 8620, has several equivalent grades worldwide, ensuring consistent properties and performance globally. These equivalents ensure the steel can be sourced and used across different regions, maintaining its quality and reliability.
AISI 8620 alloy steel is covered under various standards that specify its composition, mechanical properties, and heat treatment processes. These standards guarantee that the steel meets the required specifications for various applications.
The chemical composition of AISI 8620 remains consistent across different standards, ensuring the alloy retains its desirable properties. The typical composition includes:
AISI 8620 steel has specific mechanical properties outlined in these standards, ensuring it meets performance requirements for diverse applications. These properties include:
These equivalents and standards make AISI 8620 steel suitable for use in various industries, including automotive, aerospace, and general engineering. They provide clear guidelines for its composition, mechanical properties, and heat treatment, ensuring its consistent performance and reliability worldwide.
Below are answers to some frequently asked questions:
The chemical composition of AISI 8620 alloy steel (UNS G86200) includes the following elements: Carbon (0.18 – 0.23%), Manganese (0.70 – 0.90%), Phosphorus (maximum 0.035%), Sulfur (maximum 0.040%), Silicon (0.15 – 0.35%), Nickel (0.40 – 0.70%), Chromium (0.40 – 0.60%), and Molybdenum (0.15 – 0.25%). The remaining percentage is primarily Iron (96.895% to 98.02%). This specific combination of elements imparts the alloy with its notable properties, such as strength, toughness, wear resistance, and corrosion resistance, making it suitable for various industrial applications.
AISI 8620 alloy steel exhibits a combination of mechanical properties that make it highly suitable for applications requiring strength, toughness, and wear resistance. The tensile strength of AISI 8620 can range from 700 to 1100 MPa (101,500 to 159,500 psi), depending on the heat treatment process, with proper treatment achieving tensile strengths between 545 MPa (79 ksi) and 795 MPa (115 ksi). The yield strength typically ranges from 385 MPa (55,800 psi) to 655 MPa (95,000 psi). In the annealed condition, the hardness is generally less than 200 HBW, but after carburizing, hardening, and tempering, it can achieve a high case hardness of HRC 60-63 and a core hardness of about 35 HRC. The elastic modulus ranges from 190 to 210 GPa (27,557 to 30,458 ksi), and the shear modulus is around 80 GPa (11,600 ksi). The Poisson’s ratio is between 0.27 and 0.30. AISI 8620 has a machinability rating of about 65-66% compared to AISI 1212 steel. It also demonstrates good impact strength, with an Izod impact strength of approximately 115 J (84.8 ft-lb), and excellent wear resistance when carburized and hardened. The thermal conductivity is about 46.6 W/mK (323 BTU in/hr.ft².°F), and the melting point ranges from 2,580 to 2,650 °F (1,420 to 1,454 °C).
AISI 8620 alloy steel is widely used in various industries due to its excellent combination of strength, hardness, and wear resistance. In the automotive industry, it is commonly used for manufacturing critical components such as gears, shafts, camshafts, crankshafts, drive shafts, transmission cases, differential housing assemblies, axle housings, flywheels, connecting rods, and steering knuckles. In machinery and engineering, it is employed in the production of parts for agricultural machinery and general engineering applications, including bushings, heavy-duty pins, bolting, springs, and hand tools. The defense and aerospace sectors utilize this alloy for components that require high durability and reliability, as well as precision and high performance. In marine applications, its high chromium content provides excellent corrosion resistance, making it suitable for environments exposed to seawater or acid rain. Additionally, it is used for general machinery parts such as arbors, bearings, guide pins, king pins, pistons pins, splined shafts, ratchets, and sleeves, benefiting from the alloy’s high surface wear resistance and core strength. AISI 8620 is also ideal for precision components in firearms and aerospace industries due to its ease of machining. Furthermore, it is frequently used for applications requiring case hardening, where a hard surface layer and a tough core are needed, achieved through various heat treatment processes.
AISI 8620 alloy steel can be heat-treated through various methods to achieve specific mechanical properties. The primary heat treatment processes include annealing, normalizing, hardening, case hardening (carburizing), and tempering. Annealing involves heating the steel to 820°C – 850°C, followed by slow cooling to soften the material and improve machinability. Normalizing, performed at 900°C – 925°C, refines the grain structure and enhances machinability. Hardening is achieved by austenitizing at 840°C – 870°C, followed by quenching in oil or water to increase hardness. Case hardening, or carburizing, involves adding carbon to the surface at 900°C – 925°C and then quenching to harden the outer layer while maintaining a tough core. Tempering, done at 200°C to 704°C after quenching, reduces brittleness and improves toughness. Pre-hardened and tempered AISI 8620 can also undergo nitriding for additional surface hardening. These processes collectively enable AISI 8620 alloy steel to attain a desirable combination of surface hardness, core strength, and toughness for various applications.
AISI 8620 alloy steel performs well in terms of corrosion resistance due to its specific chemical composition, which includes chromium, nickel, and molybdenum. The presence of chromium is particularly crucial as it forms a thin oxide layer on the steel’s surface, protecting it from further corrosion. This alloy demonstrates good resistance to atmospheric corrosion, making it suitable for outdoor applications. It also withstands harsh environments such as salty water and seawater, making it ideal for marine and oil rig applications. Additionally, with proper heat treatment, AISI 8620 can endure high temperatures up to 650°F (343°C) without significant loss of properties, enhancing its durability in various industrial applications.
AISI 8620 alloy steel has several equivalent grades across different international standards. These include:
These equivalents share similar chemical compositions and properties, making them suitable substitutes in various applications.
