Induction hardening

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Induction hardening brings complex workpieces in particular to the required hardening temperature ( partial hardening ) in certain areas in order to subsequently quench them . If the heat can flow quickly enough into the rest of the still cold workpiece, no quenching is necessary. Preference is given to quenched and tempered steels achieve hardness values that come close to conventional hardening. In terms of accuracy, controllability and accessibility, induction hardening is only surpassed by laser and electron beam hardening .

Induction hardening is mainly used in tool manufacture. For example, only the cutting edge of pliers is inductively hardened, as it requires a higher hardness than the complete tool.

Electromagnetic induction : If you move an electrical conductor through a static magnetic field in such a way that the conductor intersects the field lines, an electrical voltage is induced in the conductor . Or: If the magnetic field around the electrical conductor changes, an electrical voltage is also induced in the conductor.

A coil made of copper ( inductor ) is located around the workpiece , through which cooling water runs under high pressure . If an alternating voltage is applied to the inductor , eddy currents are induced in the workpiece and the workpiece is heated with sufficient intensity. The penetration depth of the induction depends on the frequency of the alternating voltage: the higher the frequency of the voltage, the lower the penetration depth and thus also the hardening depth ( skin effect ). The degree of heating can be influenced by the current strength in the coil and the duration of the power supply. In order to keep the process times as short as possible and so that the workpiece does not heat up completely due to heat conduction , the duration of the power supply is very short (a few seconds maximum).

literature

  • E. Höhne: Induction hardening. Springer Verlag Berlin Heidelberg GmbH, Berlin 1955.
  • Gerhard Seulen: Determination of the hardening depths during induction hardening with a frequency of 10 kHz. Springer Fachmedien GmbH, Wiesbaden 1959.

See also

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