Shaft distortion as a result of local flow inhomogeneities during oil quenching in an industrial quench tank

The quenching process during the heat treatment of components can contribute to the resulting extent of distortion. Location dependencies of the oil flow in the quench tank lead to gradients in heat transfer coefficient, temperature, elongation and microstructure transformation. This can ultimately result in distortion. To gain a deeper understanding of the associated mechanisms impacting distortion the aim of the project and presentation is, to work out the relationships between flow inhomogeneities in an industrial quench tank and the distortion of gear shafts. For this purpose, oil flow-modifying measures are used to induce specific shape-changes on case-hardened gear shafts from the commercial vehicle sector, which are quantified by runout and coordinate measurements. Extensive flow measurements using impeller anemometry provide information about the existing quenching conditions resulting from the directed flow in the oil bath. In addition, shafts are quenched in a laboratory quench tank with defined inhomogeneities in the flow velocity. Recordings of the quenching process using a video camera in combination with coordinate measurements on the quenched shafts provide additional information for understanding the development of shaft distortion.

The presentation starts with an introduction to the major topic and the methodology of the work. The approaches for the local evaluation of the flow conditions at the shaft positions are then described. Based on this, correlations between the measured distributions of the flow velocity and the resulting distortion are presented. Finally, results from the laboratory tests are presented, which give insight on the role of rewetting in the development of distortion.