The basic principle of medium frequency electric furnace is a type of air-core transformer, the induction ring is equivalent to the primary winding of transformer. The metal charge inside the crucible is equivalent to the secondary winding load of the transformer. When the intermediate frequency current (2000Hz-8000Hz) is passed in the primary winding, under the action and influence of the electromagnetic field, the magnetic force wire-cut secondary winding is generated. It causes the charge to produce the induction potential, and causes the induced current to be called eddy current in the surface perpendicular to the axis of the induction ring, which causes the charge itself to heat up the metal and melt the metal. Heating for forging to forging temperature.
The change of the physical property of the metal in the heating process, the intermediate frequency electric furnace mainly refers to the change of the resistivity P and the corresponding magnetic permeability u, and the influence of the change on the current density can be seen from the calculation formula of the current penetration depth. when the magnetic field strength is constant, the relative magnetic permeability u of the steel decreases with the increase of the temperature, As the temperature continues to rise, the relative permeability u is no longer varied. When the induction heating is performed, the relative magnetic permeability decreases with the increase of the magnetic field strength when the temperature is constant. the magnetic field strength inside the conductor is non-uniform and is attenuated from the surface to the center, so that the relative permeability is increased from the surface to the center, during which the center is low due to the high surface temperature of the heated metal, As a result, the resistivity and relative magnetic permeability of each point on the cross-section are also different, and the current penetration depth is increased by 7 to 9 times as compared with the prior to the Curie point, for example, when the steel is in the Curie point.
Overseas manager: Tom Wang
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Post time: 04-08-2019