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What is induction heat treatment?

Induction heat treatment involves changing the structure of materials, usually metals, in order to improve their properties in relation to a particular application. The majority of our components are steel and the usual improvement is to harden it to make the component either stronger or more wear resistant. A proportion of components are softened, such as chain pins to enable riveting or copper electrodes to enable crimping to cable. The principle which separates Induction Heat Treatment from conventional  Furnace Heat Treatments is in the way that the heat is applied to the component. The heat in the induction process is generated in the component surface by the application of  an alternating magnetic field generated by an alternating current flowing in an adjacent copper conductor. The process may be considered as being similar to a conventional AC voltage transformer in that the adjacent copper conductor (inductor) can be considered as the primary winding of such a transformer and the secondary winding of the transformer is the actual component. The current flowing in the work piece is subject to an effect called the skin effect. Ninety percent of the induced current flow is inside this surface layer so ninety percent of the heating is within this region. The thickness of the heated layer from the surface of the metal to some point below the metal surface is inversely proportional to the frequency of the applied alternating current. Higher frequencies produce thinner skins. This property of only heating the surface is utilized to 'case harden ' the surface of steel thus increasing the wear resistance of the component without reducing the ductility of the bulk of the material.

Why use induction?

  1. Induction Heating is a GREEN process as it does not emit fumes or CO2 into the environment, emissions are controlled by the electricity generating company at one site and are easy to monitor.
  2. The result of only a small proportion of the material being heated, commonly less than 5% of the mass being heated to accomplish the required properties, then there is less energy consumed, overall, to heat treat the component when compared with conventional furnace heat treatment methods.
  3. Again due to the small areas heated there is a considerably reduced heat treatment distortion so much so that the majority of the components we heat treat are ready for assembly after heat treatment.
  4. Grinding costs can constitute 25 - 30% of the total cost of a component. Modern CNC lathes can turn components more accurately to size than they can be ground and with a better surface finish. Save money by specifying induction hardening.
  5. Some components require some areas to remain soft after heat treatment. This can only be achieved in a furnace by 'stopping off' the component. The 'stopping off  ' technique alone is usually more expensive than the cost of the induction hardening process and the induction process only hardens the portions required to be hard.