Induction heating is a non contact heating process which utilizes the principle of electromagnetic induction to produce heat inside the surface layer of a work-piece. By placing a conductive material into a strong alternating magnetic field electrical current can be made to flow in the steel thereby creating heat due to the I2R losses in the material.
In magnetic materials, further heat is generated below the Curie point due to hysteresis losses. The generated current flows predominantly in the surface layer, the depth of this layer being dictated by the frequency of the alternating field, the surface power density, the permeability of the material, the heat time and the diameter of the bar or material thickness. By quenching this heated layer in water, oil or a polymer based quench the surface layer is altered to form a martensitic structure which is harder than the base metal.
Induction hardening is a widely used process for the surface hardening of steel. The components are heated by means of an alternating magnetic field to a temperature within or above the transformation range followed by immediate quenching. The core of the component remains unaffected by the treatment and its physical properties are those of the bar from which it was machined, whilst the hardness of the case can be within the range 45 -60 HRC based on the requirement and the application. Medium / High Carbon and alloy steels with an equivalent carbon content above 0.4% are most suitable for this process. A source of high frequency electricity is used to drive a large alternating current through a coil. The passage of current
through this coil generates a very intense and rapidly changing magnetic field in the space within the work coil. The work piece to be heated is placed within this intense alternating magnetic field where eddy currents are generated within the work piece and resistance leads to Joule heating of the metal.
Induction surface hardened low alloyed medium carbon steels are widely used for critical automotive and machine applications which require high wear resistance. Wear resistance behavior of induction hardened a part depends on hardening depth and the magnitude and
distribution of residual compressive stress in the surface layer.
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