Study Of Motion And Transfer Heat Process Of Droplet And Stress Of Billet

Spray forming not only has the advantages of rapid solidification technology but also overcomes the disadvantages of rapid solidification-powder metallurgy technology, such as high cost and complicated process. But spray forming is very complex, because technology's parameters are many; these parameters interact and restrict each other. Studying the spray forming process is relatively difficult through experiments directly, and the cost is high. Numerical simulation is used to study the motion and transfer heat process of droplets,residual stress and transient stress of droplets in this paper.The mathematical model of droplet movement and its heat transfer were established for spray forming process through the analysis of spray forming process. By using the above-mentioned model, the various process of process parameter such as velocity of gas,velocity of droplet,temperature of droplet and such as solid fraction of droplet were calculated.The results shown that the velocity of atomization gas decrease with the distance increase from nozzle; and the speed of attenuation become slow gradually. The droplet is accelerated by the jet gas at the beginning, after both velocities of gas and the droplet become equal, then the velocity decrease with the drag of jet gas, and the change rule of velocity is relative to the diameter of droplet. The nucleation of a given droplet takes place when it cools down certain temperature; the temperature of the droplet ascends again after the nucleation took place, then the temperature of droplet decrease again.Utilizing finite-element technology calculated temperature field of deposition billet when it was making and made, the contemporary heating stress and residual stress of deposition billet was calculated based on the temperature field. Calculated results indicated that the cooling velocity of deposition billet is high relatively in the initial phase, it reach 102KS-1; and the transient heat stress and residual stress on the base of deposition billet is max, the max residual stress is 752MPa.