In the past years the AWT-Committee 15 (changes in dimension and shape due to heat treatment) has been investigating intensively whether it is possible to characterize heat treatment systems - i.e. the combination of furnace and quenching unit - by using geometrically simple-shaped test parts to show the effect on changes in dimension and shape of production components. The basic idea is, that distortion of components after heat treatment is caused by two aspects: The first is due to inhomogeneities and asymmetries in the microstructure, the chemical composition and the residual stresses, as they are normally generated at the production of components (steel production, forming, machining). The heat treatment only sets off the affects of earlier production steps by releasing local residual stresses, and local changes in phase transformations. The second aspect is due to uneven heat treatment. The approach is to try to eliminate the influence of the prior production steps. Such an ideally produced test part would only reveal changes in dimension and shape as a direct consequence of the heat treatment system. To check this approach, a thin walled ring of 100Cr6 (SAE 52100) was chosen as test part. 1000 rings were produced under the most identical conditions. To minimize the residual stresses, the rings were stress relief annealed in a vacuum furnace at elevated temperature. In lots of 100 parts each, the rings were subjected to different heat treatment systems under production conditions. The following report details the changes in dimension and shape of these test parts and the possibilities resulting thereof.
