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PENETRATION AND SHRINKAGE BY INTERACTION OF SOLIDIFYING CAST IRON AND THE CASTING MOLD

19730711
Journal: 39th IFC May 1972 Paper No. 8 AFS Cast Metals Research Journal (June 1973), p. 56-63
Author: H.G. Levelink & F.P. Julien

Tests made with a centrally-cored cylindrical casting have shown the practical consequences of expansion accompanying the eutectic solidification of cast iron. A surplus of liquid iron in the casting causes metal penetration into the central core, whereas metal shortage is recognizable by the presence of shrinkage defects in the casting. In these cases, the castings under study showed a sol-called "under-expansion" and "over-expansion", respectively. The type of expansion which occurs is controlled by the interaction between solidifying cast iron and the mold. Factors which promote shrinkage and decrease the tendency toward penetration are: the formation of graphite in spheroidal form, the presence of P and Mo in the iron, inoculation of the iron melt, an unstable mold wall, a convex casting shape. The amount of eutectic graphite present may act either way, depending on the type of expansion occurring. An increase in the amount of eutectic graphite promotes penetration in the case of under-expansion etc.



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