scope:

Global output of gears in the automotive industry is estimated to be in excess of 1 billion units per year.

While carburizing and quenching of steel gears for the automotive industry provides the surface-hardened teeth and flexible core necessary for a long-lasting gear, heat treating, and especially the quenching process, produces distortion. Distortion is most often corrected by the costly process of post-heat treat machining. The main goal of every high-volume gear heat treating process is the elimination of distortion. If distortion is not eliminated, the goal is significant reduction, predictability, and repeatability of distortion.

This article looks at the major causes of deformation during heat treatment and methods for controlling, correcting, and eliminating distortion. A new concept-a single-piece flow case hardening system-will be presented. This system adjusts to the size and shape of the particular gear in order to minimize distortion and ensures ideal repeatability of results, gear after gear. It is a compact system designed for high-volume gear heat treating, is ideal for lean manufacturing configurations, and can easily be integrated into machining centers.