The Pros and Cons of Induction Hardening - J.F. Heat Treating Inc

Induction hardening is a type of heat treating method in which you selectively and rapidly harden a metal surface. In the process, you place a copper coil that carries an alternating current near the part, but not directly touching it. Heat is generated close to the surface with eddy current and hysteresis losses. Then, a water-based quench (often with a polymer addition) gets directed at the part or submerged, resulting in the structure being transformed into martensite, a significantly harder structure than what previously existed.

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Modern induction hardening in Gastonia, NC is most frequently performed with a scanner. In this method, the part is held between centers, rotated and then sent through a progressive coil, which generates heat and quench alike. The quench is directed below the coil, meaning any area of the part is being rapidly cooled right after it’s heated.

Benefits of induction hardening

Here’s a quick overview of some of the benefits of this process:

• Increased strength and fatigue life: The softer core and residual compressive stress at the surface creates increased overall strength and fatigue life. This is a result of the hardened structure at the surface taking up more space than the core and the previous structure.
• Tempering: Parts can be tempered after induction hardening, which allows you to customize the hardness level according to your needs. The more you temper, the lower the hardness will be, and the lower the brittleness will be as well.
• Minimal distortion: The induction hardening process results in relatively minimal distortion to a piece of metal. Other hardening processes tend to feature a lot more warpage than what you get in the induction hardening process.
• Low cost: With induction hardening in Gastonia, NC, you can use lower-cost steels than you can in other types of hardening methods. This allows you to save money on the overall process.
• Wear resistance: The wear resistance of the parts you work on will increase significantly with the induction hardening process, assuming the material had either already been annealed or treated so it was in a softer condition.

Drawbacks of induction hardening

There are a few disadvantages of the induction hardening process to consider as well:

• Distortion: Distortion levels do tend to be larger in induction hardening than they are in processes such as ion or gas nitriding as a result of the rapid heating and quenching process and the martensitic transformation that occurs as a result. However, this distortion is still less than what you’d get from conventional heat treatments.
• Cracking: There is a greater likelihood of cracking in induction hardening than there is in other types of heat treatments.
• Material limitations: Not all types of materials can be put through the induction hardening process, so it’s not quite as versatile as some other types of heat treatments.

Induction hardening has many benefits, induction hardening can effectively improve the surface hardness of the workpiece and increase its wear resistance. Surface hardening with induction heating is a process of using the principle of electromagnetic induction to rapidly inductively heat the workpiece and then rapidly cool the workpiece. The induction heating time is short, the heating speed is fast, the workpiece is rarely oxidized and decarburized, and the workpiece is less deformed. In addition, induction hardening equipment can be easily integrated into the production line to automate the production process.

Induction hardening is often used for the surface hardening of small module gears and shaft parts, the hardening of medium and small module gears, the surface hardening of camshafts and crankshafts, the surface hardening of saw teeth, blades, and thin parts, and the surface hardening of cold rolls.

The main purpose and benefits of induction hardening of mechanical parts

1. Improve the wear resistance of the surface of the parts
Induction hardening was originally applied to the surface of crankshaft journals to improve the wear resistance of the journals. Prior to this, the crankshaft was hardened and tempered, and induction hardening greatly improved the wear resistance of the crankshaft journal.

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2. Improve the fatigue strength of parts
Induction hardening can improve the fatigue strength of hardened parts. After induction hardening of automobile half shafts, the fatigue strength was greatly improved. After induction hardening of the steering knuckle ball stud, the bending fatigue life of the part increased from 80,000 times to more than 2 million times. The induction hardening of the crankshaft fillet doubles the fatigue strength of the crankshaft, and the fatigue strength of the crankshaft of some products reaches more than 700MPa.

3. Reduce distortion
Due to the long process time of carburized gears, the distortion after hardening is large. The gears undergo induction hardening, especially synchronous dual-frequency gear hardening; the process time is short, the distortion is small, the gear accuracy is improved, and the noise is reduced.

4. Energy saving, material saving, labor saving, and environmentally protective
Parts such as gears are made of low hardenability steel and are induction hardened. First, steel has no alloying elements, saving material costs. Secondly, induction heating is local heating and hardening, and the time is short, so it saves energy. In addition, induction hardening can realize automatic online production, which saves labor, and there is no emission of harmful gases in the production process, which is more conducive to protecting the environment.

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Disadvantages of induction hardening

1) It is troublesome to match the equipment with the hardening process, because the electrical parameters often change.
2) The parts that need to be hardened must have certain induction coils corresponding to them.
3) It requires the use of specialized and strong quenching machine tools, and the cost is high.
4) Equipment maintenance is more complicated. Modular hardening equipment is now generally used, and parts are easy to replace.

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