Induction heating and temperature measurement

Induction heating is widely acknowledged as a modern, clean, fast and efficient way of heating many materials. With induction also comes accuracy of temperature, as long as the speed and power remain constant. But with more and more critical parts - such as aerospace and automotive components - being produced by this method, it is important to understand that with variances in ambient temperature and line voltage, inconsistencies of temperature can occur.

Though heating processes generally have an acceptance window for temperature, and most processes have an under-temperature and a separate over-temperature reject bin, achieving the correct target temperature is extremely important. Under-heating can cause product damage and reduce die and tool life, while over-heating of some metals can cause grain growth that has a detrimental effect on the material's inherent strength. These over-heated materials cannot be recycled through the induction process again, since the grain structure has irreversibly been altered and this can lead to premature fatigue - which could result in field failures.

The need to know if over-heating has occurred is usually of a greater importance than under-heating, since most engineering materials are polycrystalline, where, in general, grain size refinement simultaneously improves strength and durability of the material and, conversely, grain growth greatly reduces these properties.

Due to the nature of the induction process, conventional contact methods of measuring temperature - such as thermocouples - cannot be used, since they would be adversely affected by the strong induction fields. Therefore the preferred method is to use non-contact infrared pyrometers. When using a non-contact infrared pyrometer, the process becomes much more efficient and takes the guesswork out of producing consistent high-quality heat-treated parts.

It is essential to select the correct model of pyrometer to achieve accurate and repeatable temperature measurement, and guidance should be sought from the pyrometer manufacturer to ensure the correct instrument is specified.

IMPAC Infrared has over 45 years experience in non-contact infrared temperature measurement applications and has a wide range of instruments suited to the induction heating process. Contact IMPAC Infrared now for a copy of the latest product overview.