Papers by Keyword: Counter Gravity Casting

Abstract: A counter-gravity casting equipment (CGCE) has been developed, which is specially designed for the production of large-size thin-walled high-quality aluminum alloy parts with resin sand molds. In this equipment, molten metal will be pushed upward counter-gravity into the mold at predetermined rate by compressed air, and solidified at an increased pressure. The equipment uses assembled valve system developed ourselves, and has sensitive pressure-adjusting property. All of the casting parameters, including filling rate, pressure-exerting sequence, pressure hold time etc., can be closely controlled by a self-designed computer program. Up to 2 ton casting can be produced with the equipment. Compared to the castings produced under conventional gravity conditions, the castings under counter-gravity condition have generally high soundness, higher tensile strengths and ductility. The pinhole defects are also degraded obviously. The equipment and the technology have been widely adopted by several users in China for the production of large-size thin-walled aluminum alloy castings with high property requirements.

Abstract: We prepared Al-Bi alloys with our new aerogel counter gravity casting facility and Al-Pb alloys by simple mould casting with variable cooling rates. By counter gravity casting, it is possible to have directional solidification with flat isotherms and without forced melt flow during the casting process. Both methods allow studying the nucleation rate in liquid-liquid decomposition. The most important result is that a separation between monotectic and hypermonotectic particles is possible by using suitable cooling rates. The difference of the frequency maxima is a function, depending on cooling rate and starting composition. By casting experiments with variable cooling rates, we found that the average particle diameter is a function of the cooling rate, according to the theory of Ratke and Zhao, but the nucleation rate is higher than assumed in their theory.