How Mass Imbalance and Cold-Sink Effects Influence Induction Hardened Case Depth

Induction heating is very sensitive to part geometry. How mass is distributed in a part can have a strong influence on how it heats and the case depth that can be achieved. One application where this has been observed is in internal hardening of connecting rod journals. There is an uneven distribution of mass and cold-sink effect due to the rod on one side of the bore. Computer simulation of the heating and cooling processes shows how the mass imbalance affects the temperature in different areas of the workpiece, and yields insight into how the temperature history of the different areas influences the resultant microstructure after hardening. The phenomena observed may be applicable to any part having a feature to be hardened with uneven mass distribution around the feature, and principles discussed herein can aid in design of such parts for induction heat treating.