Optimization of Ring Gear Gas Quenching Process by Extracting Flow Information Encoded in Quenching Distortion

Heat treatment is a common practice in ring gear manufacturing to improve the hardness, strength, and durability. This is particularly critical for those gears used in demanding mechanical systems such as automotive transmission. However, one persistent quality issue associated with heat treatment process is the distortion, which manifests as changes in the gear’s geometry, such as warping, ovality, or tooth deformation. Distortion primarily originates during quenching, the rapid cooling stage that transforms the gear’s microstructure to achieve the required hardness. Because each region of a ring gear cools and transforms differently during quenching process due to variations in airflow and complexity of geometry, this in turn causes uneven heat transfer and leads to distortion. In addition, the outer surfaces often experience faster cooling and martensitic transformation, while the inner core cools more slowly, leading to residual stress. Because every variation in temperature distribution and cooling rate produces a specific deformation pattern, the distortion effectively encodes the thermal and flow characteristics of the quenching process in the final measurement of the dimension. This direct correspondence, which is referred to as quenching signature in this research, allows engineers to interpret distortion patterns as a diagnostic record of what occurred inside the quenching chamber. The intent of this research is to establish the relationship between quenching signatures and flow patterns in the quenching chamber using simulation on fluid dynamics in the quenching chamber and phase transformation inside the gear. By analyzing the quenching signature, engineers can reverse-engineer airflow and thermal conditions within the chamber and the results are key enablers to reconstruction of the quenching environment and optimization of airflow design.