Press Quench Process Design for a Bevel Gear using Computer Modeling

Press quenching is used to harden steel gears for tight dimensional control. The process is especially used when quenching large thin-wall gears, face gears, and bevel gears, etc.  The dimensional control aims at maintaining flatness, circularity, and radial dimensional change.  The press quench process design has been mainly based on experience, with trial and error used for implementation of new processes, new gear materials and configurations.  Computer simulation provides a means for eliminating or at least minimizing the number of try-outs that are needed to achieve the desired process results.

In comparison to the traditional oil quenching, the oil flow pattern and cooling rates along different gear surfaces in press quenching are more dependent on the die design, oil channels, and oil pump rate, and these should be considered in design of the process. Other process parameters include the die and expander loads and the locations of load application. In this paper, the process sensitivities for a press quench of a bevel gear made of carburized AISI 9310 will be assessed for reduced distortion using the commercial heat treatment software DANTE. Radial shrinkage and taper of the internal spline are observed from the trials, and the cause of the distortion is predicted and analyzed by the models. The simulation results indicate significant effects of the expander load and expander configuration.  Based on the simulation results, an effective method is proposed to control the radial shrinkage and taper distortion of the spline by using a tapered expander and locking the expander at an optimum radial position during the quenching process, which is effective for controlling out-of-round taper, and radial shrinkage distortions.