Induction hardening is widely used in both the automotive and aerospace gear industries to minimize heat
treat distortion and obtain favorable compressive residual stresses for improved fatigue performance. The
heating process during induction hardening has a significant effect on the quality of the heat-treated parts.
However, the quenching process often receives less attention even though it is equally important. DCT’s past
experiences have shown that the cooling rate, the fixture design and the cooling duration can significantly
affect the quality of the hardened parts in terms of distortion, residual stresses, and the posibility of cracking.
DANTE, a commercial FEA based software developed for modeling heat treatment processes of steel parts,
was used to study an induction hardening process for a helical ring gear made of AISI 5130 steel. Prior to
induction hardening, the helical gear was gas carburized and cooled at a controlled cooling rate. The
distortion generated in this step was found to be insignificant and consistent. Therefore, the modeling
investigation in this paper focused on the spray quench of induction hardening process. Two induction
frequencies in a sequential order were used to heat the gear teeth. After induction heating, the gear was spray
quenched using a polymer/water solution. By designing the spray nozzle configuration to quench the gear
surfaces with different cooling rates, the distortion and residual stresses of the gear can be controlled. Tooth
crown and unwind were predicted and compared for different quenching process conditions. The study
demonstrates the importance of the spray duration on the distortion and residual stresses of the quenched
gear.

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