An evaluation of gas quenching of steel rings by multiple-jet impingement

Multiple gas jet impingement cooling for quenching is a very promising approach for increasing the heat transfer coefficients (h) and thus the overall cooling rates in the gas-quenching process. Appropriate correlations for h were selected based on an extensive critical literature review, and used in a numerical heat conduction model and a numerical phase transformation model which were developed and solved for evaluating the quenching capacity of such cooling methods for quenching steel rings. The models allow prediction of the steel phase transformation extent as a function of h, for different ring sizes. An optimization of the jet nozzle dimensions and configuration was performed, and the effects of the jet spent flow and the cooling gas temperature were discussed and estimated. It was also found that while the spent flow effect on h is not adequately known, it tends to lower h, while the cooling gas temperature has minimal effect on h. Validation experiments were performed and show that the predicted trends are reasonable, within the errors of the Johnson–Mehl–Avrami phase transformation model and the experimental method used.