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Towards determining the influence parameters on the distortion of gear wheels made from the steel grade 20MnCr5 (SAE 5120), in this work the analysis of the distortion of disks is presented. The parameter identification was performed by means of the design of experiments (DoE). According to a comprehensive approach to distortion engineering, the entire manufacturing chain was considered from casting to the final heat treatment. Due to the complexity of this manufacturing chain the investigation was divided into two parts, the processes before the final heat treatment and the final heat treatment process itself. Here, in part I, the results of the investigation of the processes before the final heat treatment are discussed while in part II the results of the final heat treatment are presented. Releasing the accumulated distortion potential of the influence parameters of the processes from casting to cutting by a standard case hardening led to characteristic size changes of the disks. For the shape changes the cutting strategy showed a high influence on the change of dishing. Assuming that the cutting strategy can continuously be varied there should be a strategy for which no change of the dishing occurs, which would provide the means for compensation of distortion.

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A conventional hot rolled, low alloy carburizing steel (C: 0.21 wt.-%; Cr: 1.08 wt.%; Mn: 1.36 wt.%) has been investigated in terms of inhomogeneous phase transformations and anisotropic size changes during heating to austenitizing temperature and during slow cooling from austenitizing temperature to room temperature. A detailed study was executed on dilatometer specimens. The results were compared with the size changes of shafts with similar heat treatment. Ferrite nucleated first at selected chain-like positions and a pronounced ferrite/pearlite rodlike structure was formed. After reaustenitizing the rodlike structure appeared exactly at the same position. At intermediate transformation stages broad regions were still untransformed while other regions had an advanced transformation state. Dilatometer specimens with different orientations to the former rolling direction of the bar had different changes in length, which indicates an anisotropic size change. Cylindrical shafts showed a similar macroscopic size change like the small dilatometer specimens. For the dilatometer specimens as well as for the shafts the absolute valuese of the size change depended on the initial microstructure.

The influence and significance of several process parameters in a manufacturing chain of cylindrical bearing rings made of steel SAE 52100 (100Cr6) on the quench hardening distortion were identified using the method of Design of Experiments (DoE) and a statistical analysis of the results. The change in out-of-roundness can be explained by the used clamping technique during turning, which led to characteristic residual stress distributions in circumferential direction. Size alterations were smaller and depended also on clamping (height) resp. on clamping and an interaction of clamping and feed (radius). Other investigated factors like stirring during continuous casting, deformation ratio during forging and cooling after forging did not significantly influence shape or size changes. Density measurement was found to be a simple and effective method, to check size changes. The results confirm the necessity of concerning the whole manufacturing chain, to understand and influence heat treatment distortion. DoE has been proven to be a useful tool in this way.