The induction of eddy currents using alternating current charged coils can be used to heat conductive materials. In the mid-19th century, French physicist Leon Foucault discovered that eddy currents were produced when a conductive material is exposed to alternating electromagnetic forces. His discovery was made while studying the resistance of metal plates to movement under different conditions, but the fact that the process produced heat as a side effect was to prove one of the most important consequences of his work. These days, induction heating is used during a great many industrial and scientific processes. Here is a quick guide to some of the most important applications of induction heating.
Melting Metal
Induction heating is used in most modern metallurgy furnaces. Conductive metals are placed in a crucible, which is surrounded by coils charged by a strong alternating current. The eddy current induced in the payload metal causes enough heat to completely melt it. These furnaces do not rely upon the combustion of fuel, which means that the metals that are melted are exposed to no contaminants created during combustion. More traditional furnaces burn coke or gas in order to produce heat. Companies like cdocast.com produce special enclosed induction melting furnaces designed for laboratories and other purity sensitive environments.
Cooking
Top of the range domestic cooking hobs often use induction coils to heat pans instead of conventional electrically produced heat or the burning of gas. When a conductive pan is placed on a copper induction coil that a charge is passing through, the conductive material in the pan will heat up extremely rapidly. These hobs operate using the same principle as induction furnaces on a much smaller scale. Induction hobs are advertised as being safer and more energy efficient than their more old-fashioned gas or electric equivalents.
Hardening
Induction coils can be used to heat treat individual parts of a metal component – hardening them. This allows for products made of relatively cheap metals to be hardened selectively without needing to add additional, more expensive metals and complicating the production process. Steel, titanium and some copper alloys can be ‘case hardened’ – a process in which only the surface of a component is heated sufficiently to cause hardening. Metals can also be softened using induction heating methods, making them more malleable. Some machines are capable of hardening, softening and tempering metals – all using eddy current induction.
Shrink Fitting
Shrink fitting is a way of semi-permanently joining together two metal components in the ‘male and female’ configuration. The ‘female’ component is selectively heated using an induction coil – causing it to expand. The ‘male’ component is then inserted into the expanded concave ‘female’ component, which is allowed to cool – causing the two components to clamp together tightly. Shrink fitting is commonly used to fit electrical motor components into their housings without damaging them structurally. Shrink fitting is extremely effective at creating bonds without the need for welding or cutting. It is relatively expensive to complete and requires specialist equipment.
