The concept of induction heating has been utilized in manufacturing since the s. Nowadays, precisely controlled induction heating systems play a crucial role in the manufacturing industry. Induction heating helps expedite part production, ensures consistent high-quality results, and reduces overall costs.
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Induction hardening is a type of surface hardening process that is commonly used to increase the hardness and durability of various types of metal components. The process involves heating the surface of the metal using an induction coil, which generates a high-frequency electromagnetic field. This causes the surface of the metal to heat up rapidly, while the core remains relatively cool resulting in a martensitic transformation.
The benefits of induction hardening include:
- Induction hardening is a rapid heating process that uses high-frequency electricity to heat the surface of a metal part to a temperature above its transformation point. This results in the formation of a thin, case hardening with a tough and ductile core.
- The process can be used on a wide range of ferrous and non-ferrous materials, including steel, cast iron, brass, and aluminum.
- The increased hardness and wear resistance of the hardened surface can help prolong the service life of the part and reduce maintenance costs.
- Improved fatigue strength means that the part can withstand cyclic loading without cracking or breaking, making it ideal for high-stress applications.
- Reduced friction and improved corrosion resistance can help improve the performance and efficiency of mechanical components in harsh environments.
- Greater dimensional stability means that the part will maintain its shape and size even under extreme conditions, ensuring a precise fit and function.
Overall, induction hardening is a versatile and effective technique that can yield numerous benefits for manufacturers across many industries.
The Many Industries
Induction hardening is commonly used in the manufacturing of gears, shafts, and other components that are subject to high levels of stress and wear. It is also used to harden the surfaces of cutting tools, such as drill bits and saw blades.
In addition to the industries mentioned above, induction hardening is also widely used in the aerospace and automotive industries. It is used to harden the surfaces of engine components such as camshafts, crankshafts, and connecting rods. This process helps to increase the fatigue life of these critical components and ensures that they can withstand the extreme conditions that they are subjected to.
Induction hardening is also a popular choice for manufacturers who want to improve the wear resistance and high strength of their products. By selectively hardening only the areas of the component that are subject to stress and wear, manufacturers can reduce the overall weight of the component while still maintaining its strength and durability.
Overall, induction hardening is a versatile and effective method for improving the performance and lifespan of metal components in a wide range of industries.
A Brief Overview: Induction Heating's History
The origin of induction heating dates back to the early s when Michael Faraday discovered electromagnetic induction. However, it wasn't until the late s that the first induction heating patent was filed by Nikola Tesla. From there, induction heating technology continued to evolve with the development of new materials and the advancement of electronics.
Today, induction heating processes are used in a variety of industries including metallurgy, automotive, and food processing. Some of the benefits of induction heating include faster heating times, precise temperature control, and energy efficiency.
As technology continues to advance, it's likely that induction heating will become even more prevalent in modern manufacturing processes.
Our In-House Heat Treating Capabilities
We have the capability to heat treat your forged components internally, so you can acquire the mechanical and physical qualities necessary for your specific application or industry. Without finding another supplier to complete your heat treating – saving you time and money.
These capabilities include processes such as normalization, quenching and tempering, annealing, as well as induction hardening.
Here are some additional points to consider:
- - Normalizing is a process where we heat the component to a specific temperature and then cool it in still air. This helps to refine the grain structure of the metal and improve its overall strength and toughness.
- - Quench and temper involves heating the component to a high temperature, then rapidly cooling it in a quenching medium such as oil or water cooled. This creates a hard, brittle surface layer which is then tempered by reheating to a lower temperature. This process improves the component's wear resistance and toughness.
- - Annealing is a process where we heat the component to a specific temperature and then cool it slowly in a furnace. This process helps to relieve stress in the metal and improve its ductility and toughness.
- - Induction hardening is a specialized process where we use an induction copper coil to heat only the surface layer of the component. This creates a hard, wear-resistant surface layer while leaving the core of the component relatively soft and ductile.
Our team possesses both the necessary skills and state-of-the-art equipment to handle your heat-treating requirements with precision and proficiency.
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What is Induction Hardening?
Induction hardening is a method of quickly and selectively hardening the surface of a metal part. A copper coil carrying a significant level of alternating current is placed near (not touching) the part. Heat is generated at, and near the surface by eddy current and hysteresis losses. Quench, usually water-based with an addition such as a polymer, is directed at the part or it is submerged. This transforms the structure to martensite, which is much harder than the prior structure.
A popular, modern type of induction hardening equipment is called a scanner. The part is held between centers, rotated, and passed through a progressive coil which provides both heat and quench. The quench is directed below the coil, so any given area of the part is rapidly cooled immediately following heating. Power level, dwell time, scan (feed) rate and other process variables are precisely controlled by a computer.
Typical Induction Hardening Materials
Typical materials include:
Benefits of Induction Hardening
Increased Wear Resistance
There is a direct correlation between hardness and wear resistance. The wear resistance of a part increases significantly with induction hardening, assuming the initial state of the material was either annealed, or treated to a softer condition.
Increased Strength & Fatigue Life due to the Soft Core & Residual Compressive Stress at the Surface
The compressive stress (usually considered a positive attribute) is a result of the hardened structure near the surface occupying slightly more volume than the core and prior structure.
Parts may be Tempered after Induction Hardening to Adjust Hardness Level, as desired
As with any process producing a martensitic structure, tempering will lower hardness while decreasing brittleness.
Deep Case with Tough Core
Typical case depth is .030” - .120” which is deeper on average than processes such as carburizing, carbonitriding, and various forms of nitriding performed at sub-critical temperatures. For certain projects such as axels, or parts which are still useful even after much material has worn away, case depth may be up to ½ inch or greater.
Selective Hardening Process with No Masking Required
Areas with post-welding or post-machining stay soft - very few other heat treat processes are able to achieve this.
Relatively Minimal Distortion
Example: a shaft 1” Ø x 40” long, which has two evenly spaced journals, each 2” long requiring support of a load and wear resistance. Induction hardening is performed on just these surfaces, a total of 4” length. With a conventional method (or if we induction hardened the entire length for that matter), there would be significantly more warpage.
Allows use of Low Cost Steels such as
The most popular steel utilized for parts to be induction hardened is . It is readily machinable, low cost, and due to a carbon content of 0.45% nominal, it may be induction hardened to 58 HRC +. It also has a relatively low risk of cracking during treatment. Other popular materials for this process are /, , , ETD150, and various cast irons.
Limitations of Induction Hardening
Requires an Induction Coil and Tooling which relates to the Part’s Geometry
Since the part-to-coil coupling distance is critical to heating efficiency, the coil’s size and contour must be carefully selected. While most treaters have an arsenal of basic coils to heat round shapes such as shafts, pins, rollers etc., some projects may require a custom coil, sometimes costing thousands of dollars. On medium to high volume projects, the benefit of reduced treatment cost per part may easily offset coil cost. In other cases, the engineering benefits of the process may outweigh cost concerns. Otherwise, for low volume projects the coil and tooling cost usually makes the process impractical if a new coil must be built. The part must also be supported in some manner during the treatment. Running between centers is a popular method for shaft type parts, but in many other cases custom tooling must be utilized.
Greater Likelihood of Cracking Compared to most Heat Treatment Processes
This is due to the rapid heating and quenching, also the tendency to create hot spots at features/edges such as: keyways, grooves, cross holes, threads. (Please talk to an AHT representative if you have concerns.)
Distortion with Induction Hardening
Distortion levels do tend to be greater than processes such as ion or gas nitriding, due to the rapid heat/quench and resultant martensitic transformation. That being said, induction hardening may produce less distortion than conventional heat treat, particularly when it’s only applied to a selected area.
Material Limitations with Induction Hardening
Since the induction hardening process does not normally involve diffusion of carbon or other elements, the material must contain enough carbon along with other elements to provide hardenability supporting martensitic transformation to the level of hardness desired. This typically means carbon is in the 0.40%+ range, producing hardness of 56 – 65 HRC. Lower carbon materials such as may be used with a resultant reduction in achievable hardness (40-45 HRC in this case). Steels such as , , 12L14, are typically not used due to the limited increase in hardness achievable.
Our Burton Ave Location in Waterloo, Iowa and our Cullman, Alabama location offers Induction Hardening. Request a Quote by Filling out our Form.
* Blog was updated in July to reflect our Cullman, Alabama location now having induction hardening.
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