alloy alternating current aluminium blast furnace brazing convective heat transfer copper curie point eddy current electric current electromagnet frequency heat conduction heat treatment heating hertz hysteresis induction brazing induction cooker induction furnace induction hardening induction heater induction sealing induction shrink fitting induction welding iron joule heating metal open directory project precious metal refractory relative permeability reverberatory furnace soldering steel thermal radiation volt water cooling