What Are the Common Materials for Induction Hardening?
October 12, 2024
Induction hardening is a highly effective heat treatment process used in manufacturing to enhance the hardness and strength of a workpiece. The process involves placing the workpiece inside a coil, through which high-frequency alternating current (AC) flows, creating an electromagnetic field. The energy from this field heats the workpiece, triggering a phase transformation. The workpiece is then rapidly cooled, typically using a quenching process, which stabilizes the phase transformation (martensitic) and hardens the material.
Induction hardening can be applied to various materials, parts, and products. In this article, we will explore the common materials used in induction hardening projects in more detail.
To be suitable for induction hardening, a material must meet certain basic requirements, such as high thermal and electrical conductivity. However, only specific materials are commonly hardened this way due to the necessary microstructure and metallurgical properties.
The material should have a microstructure that allows it to harden effectively through phase transformation, which requires a certain level of carbon content. Additionally, it must possess metallurgical characteristics that enable it to retain hardness after cooling. For example, austenitic steels are not suitable for induction hardening due to their poor hardenability.
The following are the most common materials used in Induction hardening projects;
- Cast iron (>2% of carbon content)
- Medium carbon steel (0.3 to 0.6 % of carbon content)
- High carbon steel (0.6 to 1.4% of carbon content)
- Alloy steels
- Tool steel
- Stainless steel
Aluminum and titanium alloys are also compatible with induction hardening, although these non-ferrous materials are less common than other materials.
Alloy steels, tool steels, stainless steels, and other steels with at least 0.3% carbon content can be processed through induction hardening. In fact, steel is the most commonly used material for induction hardening projects. Raw steel sheets, steel parts, and products undergo this process to enhance desired properties such as strength and hardness. It is one of the most efficient methods to customize the hardness and durability of steel items to meet specific requirements.
Many steel components undergo induction hardening for surface hardening, including tools, gears, shafts, crankshafts, camshafts, bearings, bushings, axles, cylinders, pipes, and connecting rods. The hardening depth can be precisely controlled by adjusting parameters such as the current, heating time, quenching rate, and other operational settings, with depths ranging from 0.5 to 10 mm, depending on the specific application.
Alloy steel is steel that contains additional alloying elements besides carbon. Common elements such as chromium, nickel, molybdenum, and manganese are added to improve the steel's strength, hardness, toughness, and corrosion resistance.
Several grades of alloy steel are used in various induction hardening projects. A steel grade refers to a specific standard or classification that defines the steel's composition and properties, tailored to suit different applications. These grades are selected based on their ability to achieve the desired hardness and durability after the induction hardening process.
Grades | Description |
1045 | It is a medium carbon steel alloy with 0.43-0.50% carbon content and other alloying elements. The SAE 1045 steel can be hardened through induction heating to increase its strength and hardness. Although, with lower hardenability, it may not be suitable for specific applications with a very high surface hardness. |
1050 | Alloy steel 1050 is a medium-carbon steel alloy composed mainly of Manganese, carbon, and iron. It has a lower carbon content than 1045 steel, which means it is softer and less hardenable. |
1144 | It includes manganese and sulfur in addition to carbon as an alloying element. The ability to be stress-relieved without becoming brittle makes it unique. |
4140 | A low-alloy steel that is known for its good strength and toughness. The steel can be induction hardened to achieve a surface hardness of up to 58HRC (typical value). It has a relatively low hardenability compared to other high-alloy steel. |
4340 | It is a high-alloy steel with high strength and hardness, suitable for crankshafts, connecting rods, and other high-stress parts. Additionally, the addition of nickel in the alloy provides better toughness and ductility at high strength levels. |
5210 | It is a high-carbon alloy steel, and this high carbon content makes it suitable for induction hardening projects. This grade is used in high-performance applications after induction hardening that requires high surface hardness, such as bearings, gears, and cutting tools. |
8620 | 8620 is a low-alloy steel commonly used in induction hardening projects. It is hardened to achieve different properties, strength, hardness, and fatigue life. |
9310 | It has a relatively high hardenability compared to other alloy steels, making it an excellent choice for induction hardening in applications with very high hardness. |
As previously noted, steel must contain at least 0.3% carbon to be suitable for induction hardening. The carbon content plays a crucial role in this process, as it primarily determines the hardness and depth of the hardened layer. Steels with higher carbon content can be hardened to a greater depth, resulting in increased hardness but also more brittleness. In contrast, low-carbon steels are softer and more ductile, limiting the depth to which they can be hardened.
The depth of the hardened layer is critical in induction hardening, as it influences the component's strength and wear resistance. Additionally, carbon content affects the transformation temperature during the process. Steels with higher carbon content require a higher transformation temperature to convert austenite into martensite, which is essential for achieving the desired hardness.
Selecting the right material for induction hardening is crucial to ensuring optimal performance and meeting the specific requirements of the application. The process depends on factors such as application needs, material availability, and processing capabilities. Here are the key steps involved in the material selection procedure:
Begin by determining the specific needs of the application, including strength, hardness, wear resistance, toughness, and ductility.
Based on these requirements, compile a list of potential materials and alloys. These options typically vary in carbon content, alloying elements, and microstructures.
Assess the induction hardening potential of each material. Consider factors like transformation temperature, hardness, depth of the hardened layer, and susceptibility to cracking.
Compare the mechanical properties of each material, such as strength, toughness, hardness, and ductility, to ensure they align with the application’s requirements.
Analyze the cost and availability of each material option, considering raw material costs, manufacturing expenses, and lead times.
After evaluating induction hardening capabilities, mechanical properties, and cost factors, choose the material that best fits the application.
Common materials used for induction hardening include cast iron, medium- and high-carbon steels, alloy steels, tool steels, and stainless steels, with steel being the most frequently used. Selecting the right material is essential, as it directly impacts the quality and performance of induction-hardened parts or products. When choosing a material, consider the desired properties, application, hardening potential, cost, and fatigue life to ensure optimal results for your project.
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