The process of case hardening of steel includes three consecutive steps of heat treatment: heating; the thermochemical process with the enrichment of the surface area during the carburizing or carbonitriding stage with carbon and nitrogen; and the subsequent quenching process for hardening. This article provides a model-based description of the development of residual stresses during case hardening. It also describes the influence and effects of residual stresses and distortion in hardening, carburizing, and nitriding processes of the steel.
This article presents the three levels of investigations of distortion engineering. On Level 1, the parameters and variables influencing distortion in every manufacturing step must be identified. More than 200 parameters can affect distortion. The design of experiments approach allows for the investigation of larger numbers of parameters by a limited number of samples, and can be structured into system analysis, test strategy, test procedure, and test evaluation. Level 2 focuses on understanding the distortion mechanisms by using the concept of distortion potential and its carriers. Distortion engineering aims to compensate distortion using the so-called compensation potential (Level 3). Level 3 discusses the measures to improve homogeneity, and respectively the symmetry, of the carriers of the distortion potential. The article also discusses the compensation of the resulting size and shape changes of the existing asymmetries by well-directed insertions of additional inhomogeneity/asymmetries in one or more of the distributions of the carriers.