D. S. MacKenzie, Houghton International, Inc., Valley Forge, PA

Summary: Heat treating and quenching are arguably the most critical operations in the manufacture of gears. It is these processes that provide a gear with the proper mechanical and wear properties to withstand high contact stresses and have high longevity. Unfortunately, heat treating and quenching are often the least understood in the manufacturing stream. Parts after heat treatment are often distorted or stained. It is often the “black-hole” that all the ills of the manufacturing process are blamed. It is the purpose of this article to examine the causes of distortion during the heat treatment and quenching of gears, and provide some insight into proper corrective action to correct distortion and high residual stresses during quenching.