TECH-TIPS   (spring03 update)       

Induction Heating is a process where electro magnetic energy delivered in the form of a water cooled copper coil causes molecular excitation in metallic materials. It is fast and can be localised to quickly heat specific areas - or slow for large parts using a large coil and power generator.

Typically this heat treatment process is used to change the physical and metallurgical properties of the product as in annealing, hardening, melting, forming, brazing, welding, coating and drawing.

A Typical Problem

When the induction heating is not capable of providing a repeatable temperature from part to part using a combination of time and power level, then closed loop control system with infra-red sensor is required. The need for temperature control can be due in part to inconsistent fixture, part variance, power variance, very short time cycles, small parts, or many other variables that have tighter control limit requirements to deliver consistent quality parts.

For many basic applications, a simple time cycle is usable where the temperature window is not as critical, the time cycle is long, and/or part alignment is a simple fixture. In this applications setup and recorded documentation may be an issue so product temperature monitoring is a requirement. Heat treating is normally at the end of the process so rejects can be costly and you can generate a lot of scrap or re-work in a hurry.

The Solution

Induction (resistant to flame) heating systems are used to accelerate heating rates to run faster, do localised heating or supply high powered energy in restrictive areas. With a rapid heating capability, precise temperature control parameter to achieve consistent quality. An infrared thermometer is used when accuracy and repeatability is critical. Temperature monitoring is important for new applications involving OEM accounts and in-house retrofits as part quality demands are more stringent.

For low temperature, low emissivity applications, the short wavelength sensors with auto null balancing will do the job. The preference is to use fibre optics like the PRO 52 with built in light , or visual/ laser aiming with the PRO 42. Low temperature sensors operating in the longer wavelength are very emissivity sensitive and will not be accurate enough to control the process.

For high temperature application ( >200 deg C) the dual wavelength design provides automatic emissivity correction, measures the hottest temperature in the field of view, looks through dirty optics, quench fluids and contaminated media. These are very critical application problems as the fast heat will for example significantly change the surface emissivity and also create scale issues so dual wavelength PRO 90 series is often used for easy alignment using the built-in aim light add accessibility where space is limited.

If non-ferrous materials like aluminium, copper, brass and zinc are the target then the multi wavelength PRO 120 / 220 is required.