FUNDAMENTAL CHARACTERISTICS OF METAL FLOW IN THE FULL-MOLD CASTING OF ALUMINUM ALLOYS (LOST-FOAM; POLYSTYRENE).

摘要

The kinetics of degradation of solid expanded polystyrene in contact with liquid aluminum have been measured as a function of temperature. The respective rates of vaporization and of gas production are equal to 0.077 ;The flow characteristics of different metals in horizontal and vertical strips have been investigated with a computer-aided multiprobe thermometric technique. Metal velocities in full-molds are found to increase with the melting point of the material and are significantly lower than the values observed in empty-cavity molds. The effects of metallostatic head, pattern geometry, pouring temperature and several mold variables on the flow behavior have been studied. Velocities at the metal front are generally of the order of 10 cm/s while values of up to 60 cm/s have been measured at the ingates in side-gated plate patterns. The data accumulated have been used successfully to predict the pattern of metal flow in simple full-molds.;The endothermic losses occurring at the metal front have been calculated from the responses of thermocouples placed along the path of the metal. It has been shown that steep thermal gradients exist in the liquid metal after the mold is filled. From an analysis of the cooling curves, it has been established that flow is choked at the metal front and that directional solidification is achieved. A straight-channel fluidity test has been devised and used to measure the fluidities of several commercial foundry alloys as a function of various metal and mold variables. A simple mathematical model has been developed to obtain the temperature history of the metal at any location in the mold and to predict the fluidity of the metal.