Economic surface hardening by spray cooling

Abstract

The objective of the current investigation is a cost analysis of spray cooling based on the assessment of a machine-hour schedule. Here, a gear toothed component is used as an example which is induction hardened by means of the simultaneous dual frequency method and compared with conventional polymer quenching. By using hardness measurements and light-microscope examinations, it is demonstrated that comparable results are obtained for the induction hardening by employing spray cooling and those by polymer quenching. By investigating the influence of the spray's parameters on the hardness results, it was possible to draw inferences regarding the ratios of water to air pressures which lead to the desired hardness profiles. Estimating the costs of employing the two quenching methods have shown that the spray cooling is the more cost-effective of the two methods.

Induction Heat Treatment of Sheet‐Bulk Metal‐Formed Parts Assisted by Water–Air Spray Cooling

“…Through variation of the spray parameters, such as the water and air pressures, the heat transfer coefficients at workpiece's surface can be precisely adjusted over a wide range, which is typically between those achieved by gas and immersion quenching . A detailed study of the resulting heat transfer coefficients regarding the variation of spray parameters, the number of nozzles, and the overlapping of spray cones is given by Herbst et al By employing water–air spray cooling, the mechanical properties, such as tensile strength, can be improved, the distortion during quenching can be reduced, and the residual stress state can be adjusted. In previous investigations using conventionally formed gear wheels made from 42CrMo4 hardening and tempering steel, it could be demonstrated that compressive residual stresses can be induced in the loading‐relevant regions of the tooth's flanks …”