关键词: 风冷淬火, 界面换热, 淬火初始温度, 表面介质流量密度, 表面粗糙度

Abstract: The heat transfer process of high-speed gas impact on the hot metal surface was studied through a series of air-cooled quenching experiments. The inverse heat transfer method was used to calculate the interfacial heat flux(q) and the interfacial heat transfer coefficient(h). The effects of initial quenching temperature of specimen, surface roughness and air flow density on specimen surface on heat transfer process were studied. The results show that the initial quenching temperature of specimen has a significant effect on the heat transfer at the air-cooled quenching interface. When it increases from 470 ℃ to 520 ℃, the maximum value of both q and h is increased by about 50%, and the average cooling rate of quenching surface temperature, when decreases to 200 ℃, is increased by about 43%. With the increase of the air flow density on specimen surface, the interfacial heat exchange shows a tendency of first increasing and then decreasing, that is, when the interfacial heat transfer efficiency is highest, there is a critical air flow density on specimen surface corresponding to it, and the closer the injection angle is to 90°, the smaller the critical value is. As the surface roughness of the specimen increases, the interfacial heat transfer decreases continuously, which may be attributed to the more obvious the rougher surface pinning effect on the fluid in the boundary layer, the more unfavorable it is to improve the interfacial heat transfer efficiency. Moreover, in the range between 250-380 ℃, there is generally a depressed region in the curve of h with surface temperature, which may be related to the precipitation of secondary phase during quenching and cooling of aluminum alloy.

Key words: air-cooled quenching, interface heat transfer, initial quenching temperature, surface air flow density, surface roughness