科研之友
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摘要
In permanent mold casting, die design for cast aluminum alloy and magnesium alloy products includes a number of high conductivity material cooling blocks (also called cooling circuits or chills) that are aimed to extract heat away from molten metal through direct conduction heat transfer and freeze the casting as quickly as possible in a directional manner. One of the biggest problems during this solidification process occurs when the molten metal naturally shrinks away from the mould as it solidifies. This makes it increasingly difficult to efficiently and effectively cool targeted areas in the casting through conduction, because the direct contact between the solidifying casting and the cooling block is significantly reduced or even lost. This can create millions of dollars of waste in terms of casting rejects, lost productivity, and reworks for a given manufacturing company. A movable water cooled copper chill was designed and built to push into an insulated mold during the solidification process. The experiments were carried out using commercially available A356 aluminum alloy. The chill was squeezed into the casting at various times during the solidification cycle. Studies were carried out to understand the effect of a movable water cooled chill with different cooling conditions compared to a typical fixed chill. Numerical simulations were conducted using developed boundary conditions in a commercial casting solidification package (ProCAST (TM)). The resulting sensitivities of the casting due to different chill conditions (i.e. fixed vs. moving) are described through physical phenomenon, metallo graphic analysis and computational modeling. Experimental results indicate that the air gap formation can be reduced using a movable chill and a higher heat removal rate can he achieved, thereby reducing the solidification time and hence improving productivity of a given casting. The effective solidification time with a movable water-cooled chill has decreased by over four times compared to a fixed water cooled chill which is at present being used in the industry.
- 出版日期2011
