金属材料喷雾淬火过程的界面热交换分析

通过末端淬火试验,对铝合金试样喷雾淬火过程的界面热交换进行了研究。采用反热传导法求解了所有试验的界面热流密度(q)和界面传热系数(h),重点分析了喷雾压力、喷嘴直径和试样表面粗糙度对界面热交换的影响。结果表明:喷射压力对整个淬火界面换热过程均有影响,但对过渡沸腾阶段影响更大,且喷射压力越大,q及其峰值q_max越大,进入核沸腾阶段的时间越短;喷嘴直径越大,q、q_max越大,越早进入核沸腾阶段,但增大喷嘴直径对界面换热的影响存在上限;随表面粗糙度增大,q、q_max先减小后增大;在本试验条件下,上述喷射压力、喷嘴直径和表面粗糙度对界面热交换的影响规律均不受另外两个参数取值的影响。此外,由于喷射的微小液滴均匀覆盖了整个热表面,产生了剧烈的核沸腾,导致在部分试验中,q曲线在核沸腾阶段出现了二次升高现象。

Interfacial heat exchange analysis of metal materials during spray quenching process

The interfacial heat exchange of aluminum alloy during spray quenching process was studied by end quenching test. The interfacial heat flux (q) and interfacial heat transfer coefficient (h) of all the tests were solved by inverse heat conduction method. The influence of spray pressure, nozzle diameter and surface roughness on the interfacial heat exchange was analyzed. The results show that the spray pressure has an effect on the whole quenching interface heat transfer process, but it has a greater effect on the transition boiling stage. The larger the spray pressure, the larger the q and its peak q_max, and the shorter the time to enter the nucleation boiling stage. The larger the nozzle diameter is, the larger q and q_max are, and the earlier the nozzle enters the nucleation boiling stage. However, there is an upper limit on the effect of increasing the nozzle diameter on the interfacial heat transfer. With the increase of surface roughness, q and q_max decrease first and then increase. Under the experimental conditions, the effects of spray pressure, nozzle diameter and surface roughness on the interfacial heat exchange are not affected by the other two parameters. Under the experimental conditions, the influence of any of the above three parameters, i.e. spray pressure, nozzle diameter and surface roughness, on the interfacial heat exchange is not affected by the other two parameters. In addition, the second increase of q curve during the nucleation boiling stage is resulted in some experiments due to intense nucleation boiling caused by the sprayed droplets with very small diameter uniformly covering the whole thermal surface.