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High Frequency Heat Treatment

High Frequency Heat Treatment Technology

Simply stated, high frequency quenching is a heat treatment that involves heating or cooling only the necessary area of a part. This is also referred to as induction hardening and abbreviated IH.

A quick overview of this process is explained below.

(1)Use electromagnetic induction

Electromagnetic induction involves placing two coils close to one another--Coil A connected to a power source and Coil B isolated (both coils do not contact one another)--and then creating a magnetic field by switching the power source on, which immediately induces a current of electricity in Coil B as well. The same phenomenon occurs when the power is turned off. The inducement of electricity in Coil B is referred to as the electromagnetic induction phenomenon.

(2)Apply heat to the part using an induced current of electricity

Using the current of electricity induced through electromagnetic induction (eddy current), Coil B is replaced with the actual part (metal) into which the current of electricity will flow.
Resistance will produce Joule heat when the current of electricity flows into the part, causing the part itself to heat up. In this manner heat is applied efficiently using the direct-heating application method.

(3)Apply heat only to the required area and depth

Heat is then applied only to the necessary area by machining the shape of Coil A to mimic the shape of the area of the part requiring heat treatment.
The higher the frequency of the power source, the more the induced current of electricity will concentrate on the surface of the part. This is referred to as the skin effect. The frequency can be selected according to the part shape (size) and the desired depth of the hardness.

The ONEX Advantage

The range of the frequency used in this process is between 20 and 400kHz, or medium to high frequencies. For the oscillation source, we use a vacuum tube in order to treat a full range of part sizes, from oversized to precision components. For shaft parts, robots enable simultaneous quenching on up to four axes. We are also able to treat parts that pose a challenge for the production line, such as multi-stage v-groove pulleys. Since the heating coil is machined in house (some parts are machined externally), we can shorten the lead time up until trial treatment. For the cooling medium, we use not only aqueous solution, but also oil coolers, which enable us to treat large gears as well.
Another one of our advantages is that we offer thermal refining, carburizing treatment and gas nitrocarburizing treatments within the same plant, meaning we can easily accommodate hybrid treatments involving carburizing and high frequency quenching, gas nitrocarburizing and high frequency quenching.

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