Similarity Analysis Applied to the Die Casting Process

Abstract

Detailed studies of the filling process of the die with liquid metal and the solidification are necessary to put this technology on a firm scientific basis. An experimental study of the fluid flow, heat transfer, and solidification encounters, however, enormous difficulties. It is extremely fast [in order of milliseconds], the small scale of the die makes local measurements difficult, and the temperature range and the nature of the liquid metal does not lend itself readily to experimentation. This paper explores whether similarity analysis is useful for the design of model experiments which reduce these difficulties and which reproduce the actual occurrence faithfully. The study is carried out in two steps. During the initial period, the whole cavity of the die is available for the fluid. Reynolds and Weber numbers which have to have the same value for the model experiment and for the die casting process permit the use of any fluid and of a large scale model which decreases the injection velocity and increases the filling time. During the later period of the filling process the cavity available for the liquid is reduced by the solidified metal. The energy conservation equation results in two more dimensionless numbers, the Prandtl and Jakob numbers which prescribe that model experiments have now to use a liquid metal but use of a metal with a low melting point and of a large scale decrease again the required injection velocity and increase the filling time by orders of magnitude, conditions beneficial for detailed and accurate experiments.