In view of the prominent problems of poor cooling capacity and uniformity of the rail air-quenching technology,supersonic profiling nozzle(SP nozzle)was designed to improve the cooling capacity through supersonic jet and improve the cooling uniformity through the profiling structure of the rail head,and then the effect of heat transfer characteristics of SP nozzle on the rail was studied by using the numerical simulation combined with experiments.The results show that the cooling capacity of the SP nozzle is 54.22％,13.88％and 47.01％higher,and the cooling uniformity is 31.11％,31.11％and 6.06％higher than that of the existing circular constant velocity nozzle,circular supersonic nozzle and constant velocity profiling nozzle,respectively.In the production,the following measures are beneficial for improving production efficiency while ensuring the performance of the rail:adjusting the inlet pressure of the SP nozzle to cool the rail at a rate close to but not greater than the critical cooling rate of the pearlite transformation before cooling to the end temperature of phase transformation(about 500 ℃),and then increasing the inlet pressure as much as possible.
U75V steel railheat treatmentsupersonic profiling nozzleheat transfer characteristicsnumerical simulation
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