Nonrotational Induction Crankshaft Hardening Capabilities Extended

Advanced nonrotational induction crankshaft hardening process (SHarP-C, or stationary hardening process for crankshafts) has become a proven process for V-6 crankshafts. The main features of the first machine that provided the heat treating for V-6 crankshaft journals using stationary inductors rather than the cumbersome methods of the conventional crankshaft hardening processes were discussed previously [1]. Advantages of the process include a short heating time (2 to 4 seconds), a reduction of floor space requirements (as much 80% in some cases), a four-fold increase in tooling life, a reduction of machine-life-cycle cost and better crank-performance characteristics. SHarP-C technology has progressed into a proven process for treating a family of different crankshafts. This article provides general information of the stationary induction crankshaft hardening/tempering process concentrating on the features of V-8 crankshafts (Fig. 1), and compares the main features of the nonrotational and conventional processes.

Most existing induction crankshaft hardening machines require crankshaft rotation during heating. The crank is rotated about its main axis while each crankpin and main journal is heated by bringing a "U"-shaped inductor close to the pin or main bearing surface (Fig. 2). The inductor and other massive components of the induction hardening machine must travel with the orbital motion of the connecting-rod journals. The circular orbital motion of such a heavy system must be precisely maintained using a special control tracking system that provides a power variation for each heated crank feature during its rotation.