Improvements in or relating to methods for the induction heating of metals, with recovery of the energy that is dissipated within the inductor, and heating equipments operated according to such methods

摘要

Workpieces are induction heated, e.g. steel billets to 1200 DEG C or aluminium ingots L to 500 DEG C., by applying A.C. to an inductor coil 10 e.g. of copper tubing in a heating unit Ri, cooling the coil e.g. to 250-300 DEG C. by heat exchange with a fluid which is then used to preheat the workpieces, e.g. to 200 DEG C. in an heat exchanger Pr comprising a salt bath 12 or other liquid, before inductively further heating them in the coil. The fluid, which is preferably circulated in a closed circuit through the inductor coil and pipes in the heat exchanger, may remain in its liquid state at the temperature attained by taking up heat from the inductor, or be converted into its vapour state and then brought again to its liquid state at the temperature of heat exchange with the workpieces. Alternatively a gaseous fluid such as air may be used. Examples of cooling fluids are eutectic mixtures of diphenyl and diphenyl oxide, water and salt baths. The workpieces may be automatically advanced through the heat exchanger by a conveyer chain, then through the inductor by a hydraulic piston 16, the temperature attained by the workpiece controlling the operation.