Induction Hardening

  • Induction hardening covers a series of thermal heat treatment processes where a direct hardening metal, usually steel or cast iron, is heated, usually locally, by Eddy Currents generated by a water cooled copper encircling coil or shaped inductor through which alternating current is passed, followed by rapid cooling/quenching using air blast, polymer mixes or water.
  • Frequency, power, distance between inductor and work-piece, and the design of the coil or inductor control the locality and depth of penetration of heat.
  • Induction hardening is used to increase the mechanical properties of ferrous components in a specific area.
  • Examples of the use of induction hardening include contour or flank-only hardening of gears, ring-coil/spin hardening of smaller gears, shaft surface hardening, and local hardening of specific surfaces on components such as track pads, drive pulleys etc.
  • Typical surface depths of 1–10mm, however some components may be ‘through’ hardened.
  • Induction heating can also be used for localised tempering or softening of the work-piece.
  • This localised treatment offers minimal distortion and can produce a high surface hardness with a deep case which is capable of handling extremely high loads.
  • Improves wear and resistance to cracking by fatigue or similar mechanisms.
  • Reduces post Heat Treatment processing (grinding etc).
  • When used for surface hardening, base material properties are unaffected allowing for conventional machining to be carried out away from the hardened zone.
  • Automated induction hardening is achieved with programmable, computer controlled machines which ensure reliable and consistent hardness levels, and therefore a quality product.
  • We offer bespoke manufacture of coils.
  • Ability to locally harden selected areas of steel (sometimes cast iron) leaving the remainder of the component unaffected – dependent on material and hardening parameters.
  • Where core properties are deemed less important, cheap medium carbon steels (eg. 080M46) can be used and locally/surface hardened to high hardness >58 HRC.  An example of this might be a roller requiring wear and indentation resistance.
  • Induction processes provide the ability to surface harden components that are too large to case harden using gas carburising or similar furnace treatment methods (tooth hardening of large gears, local hardening of wear pads on large links etc).
  • Keighley Laboratories can handle components varying from large gears, (3000mm maximum diameter and 2500Kg weight) – including helical and some bevel gears, to large numbers of small automotive components such as turbocharger wheel shafts. 
  • Typical components include, shafts/pins, Bevel, Helical and Spur gears, Internal Bore hardening dependent on size.
  • Considerable development effort has been put into the tooth hardening of different gear types, previously considered as un-hardenable by these methods.
  • Induction hardening is not restricted to simple plain medium carbon steels.  with many quenched and tempered low alloy steels, martensitic stainless steels, specific tool steels and SG cast irons also capable of being hardened by this method.
  • Typical carbon and alloy steels processed include; 080M40 (EN8), 070M55 (EN9), 708M40 (EN19), 817M40 (EN24), – these latter two are low alloy steels and should be quenched and tempered condition for optimal results, and 534A99 (EN31), also some specific stainless steels, cast irons (grey irons), ductile irons and malleable irons.
  • Not all materials are suitable for induction hardening – advice should be sought at the design stage.

James Menzies


Leonard Powell

Technical Planner

David Wright

Production Director

Keighley Laboratories Ltd
Registered Office:
Croft House
South Street
West Yorkshire
BD21 1EG
Registered in England 164811
UK Tel: +44 (0)1535 664211

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Service Type
Induction Hardening
Provider Name
Keighley Laboratories,
Croft House South Street ,Keighley,West Yorkshire-BD21 1EG,
Telephone No.+44 (0)1535 664211
Keighley, West Yorkshire
Induction hardening covers a series of thermal heat treatment processes where a direct hardening metal, usually steel or cast iron, is heated, usually locally