Abstract
One of the causes of quenching cracks is regarded to be the stress that occurs owing to quenching. Quenching stress is affected by the material shape. In order to prevent the quenching crack in a polymer quenching process, it is important to understand the relationship between the material shape and the quenching stress. Therefore, the relationship between the flange thickness of a flange shaft and the quenching stress was investigated. As a result of quenching stress analysis, it was confirmed that the radial stress increased with decreasing flange thickness. Then, a quenching test utilizing test material corresponding to an actual product size was conducted and the residual stress was measured after quenching. The radial residual stress increased with decreasing flange thickness, and this tendency corresponds to the result of the quenching stress analysis. In addition, the generation mechanism of the quenching stress was considered using the results of quenching stress analysis. As a result, the causes of quenching cracks have been found to be not only time lags of the martensitic transformation between the surface and the inside along the axial direction, but also the difference in the transformation behavior between the flange part and the shaft part.
