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Metal Casting Technologies : March 2010
caused an asymmetrical temperature distribution within the liquid metal during filling which led to the formation of porosity. Simulation of the current process confirmed this suspicion. The initial metal on the downward side of the casting was quite hot while, due to the aggressive cooling of the mould, the metal filling the far side of the mould was substantially colder. This temperature distribution led to formation of an isolated hot spot on the side of the casting which filled first; this hot spot was the reason for porosity formation, as shown in the following Figures 4 and 5. After the initial simulation, it was decided to reduce the filling time (i.e., speed up the tilt pour) of the mould in order to decrease the temperature difference across the casting. The thickness of the top riser was also increased in order to improve feeding during solidification. Simulation of this modified process design showed that formation of the isolated hot spot was substantially decreased, and the potential for shrinkage porosity formation was eliminated. METAL Casting Technologies March 2010 45 Fig 5. Prediction of porosity in the solidified casting Fig 6. Tilt Pour and Solidification Simulation with faster pour and enlarged riser
Media Kit 2010