Verfahren und Vorrichtung zum induktiven Waermebehandeln von Werkstuecken aus Stahl

1,178,338. Heat treatment process and apparatus. AEG-ELOTHERM G.m.b.H. Feb.13, 1968 [April 29, 1967], No.7139/68. Heading C7N. [Also in Division H5] An elongate workpiece of varying diameter is heat-treated to produce a region which is toughened throughout its cross-section and a portion which is surface hardened by first heating the workpiece non-uniformly along its length by relative movement of it and an inductor, and then heating it by induction uniformly along its length, including the region that was first heated; the workpiece is then hardened by quenching. Apparatus for carrying out the process comprises one or more inductors and means for moving them along the workpiece, including means for reversing or retarding their motion in the region to be heattreated; there may also be means for controlling the power and/or frequency of the current supplied to the inductors according to the position of the latter in relation to the workpiece. In the embodiment illustrated, inductor 3 is caused to heat that region 8 of workpiece 7 which is to be throughhardened, while inductor 6 travels to the flanged end of the workpiece, and then moves slowly upward, heating the surface zone 9 which is then quenched by spray 13. Conditions are such that when inductor 6 reaches inductor 3 zone 8 will have been heated throughout, and the two inductors then move from the workpiece together. Movement of the inductors over the workpiece may be repeated to effect annealing and/or tempering.