Metallurgical Aspects of Distortion and Residual Stresses in Heat Treated Parts

While modeling of quenchant behavior and microstructural response has matured, the sensitivity to variation of common metallurgical and production practices are often not considered.  As an example, the variation in hardenability of the purchased material is generally not considered when predicting microstructure and residual stress.  Machining practices, including worn tools and use of tooling beyond the expected life can have dramatic influence on distortion and residual stress.  The quench oil chosen, and the quench part are all important variables to consider. Finally the presence of adjacent parts and the racking method can also effect the residual stress state and distortion. The effects of common metallurgical variables on the residual stress and distortion of heat treated parts are reviewed.  Factors such as hardenability, segregation, and rack and fixture design are discussed.