Simulation of Cooling Rate of Gray Cast Iron Casting in a Sand Mold and Its Experimental Validation

摘要

Estimation of cooling rates of gray cast iron casting in the sand mold and its dependency on design and process parameters is one of the keys for achieving best processing conditions to produce quality castings. The estimation of cooling rate involves modeling of fluid flow, heat transfer and solidification of molten metal inside the mold. Prediction of heat transfer has been carried out from filling of mold but the estimation of cooling rate has been carried out after complete filling of the mold. In the present work fluid flow, heat transfer and solidification of molten metal in a sand mold model has been developed on a Pro-Cast 2008 platform. A stepped bar pattern with different thickness has been fabricated to carry out the experiment. Stepped bar pattern has been selected because gray cast iron castings are thickness sensitive as well as different section of castings have different cooling rate. Cooling rates have been determined experimentally by measuring the Dendritic Arm Spacing (DAS) and Secondary Dendritic Arm Spacing (SDAS) from the microstructure of different steps. Results show that the morphology of graphite, dendritic arm spacing and secondary dendritic arm spacing as well as the interlamellar spacing of eutectic structure depend on the casting thickness. These decreases as the thickness of castings decrease because thinner section of casting has higher rate of cooling than the thicker section. The estimated cooling rate matched well with the experimentally measured cooling rate.