Ring gear distortion from heat treatment processes has been a challenge to gear manufacturers. To provide good post heat treatment dimensions, efforts have been made to optimize post heat treat controls such as quench apparatus, quench severity and post heat treatment grinding. However, the impact of prior-to-heat treatment gear microstructure is not fully understood.In this study, ring gears with different prior-to-heat treatment (initial) microstructures were compared against post-heat treatment dimensional measurements. Statistical analyses were performed on data collected over 2 years at a production facility. Heat treat growth was found to be strongly affected by the initial microstructures and green hardness. Recommendations were made to help reduce heat treat growth variation.
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