Mould-metal movement in a horizontal sand mould

Six types of green sand were prepared with different mulling times and different compositions; with additions of bentonite (C sand), bentonite and seacoal (S + C sand), bentonite, seacoal and reused dust (S + C + D sand). Six batches of green sand and CO₂ core sand were used to make standard sand specimens (50 mm in diameter and 50 mm in length). The whole sand mould was made of CO₂ core sand and the prepared standard sand specimen was set at the smaller end of the bar cavity. The movement of the metal/sand specimen interface was measured, after molten gray iron was poured into the mould cavity, to produce a horizontal bar casting. For short-mulled green sand containing combustible seacoal, the measured deformation curve indicated that an apparent expansion of the mould-metal interface occurred for a period of time after the sand specimen came into contact with the molten iron. This expansion was in relation to the percentage of moisture absorbed in green sand and the ratio of green compressive strength and green shear strength. The mechanism for the expansion of the mould-metal interface was schematically explained and discussed. The contraction of the mould-metal interface as measured at 300 seconds after filling, was inversely proportional to the tested AFS clay and green shear strength of the sand specimen.