Abstract: The present invention discloses a method for contour hardening a gear by means of induction heat treatment in a single heating cycle, using a single frequency of induction current. The typical frequency of alternating current is 50 KHz, applied in a single heating cycle for a duration in the general range of 0.3-1.0 seconds, having a power in the typical range of 200-1,000 KW. The power level required for any particular gear is typically 120% to 150% that required in the final heating step of a hardening process which requires preheating. An important advantage of the process disclosed herein is the elimination of the need to preheat the gear, yet contour harden tooth and root regions of said gear with a single heating cycle of a single frequency heating current.

Abstract: This invention relates to a method and apparatus for the induction heat treatment of conducting workpieces. More particularly, this invention relates to an apparatus and method for heat treating irregularly shaped workpieces lacking rotational symmetry about a central axis. The heat treatment applied by the apparatus or method of the present invention effects the surface of the workpiece substantially uniformly at all points around the perimeter of a workpiece lacking rotational symmetry, and accomplishing such substantially uniform heat treatment without requiring excessive current flow, without requiring interruptions of large current flow.