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Fig. 5. Holes drilled into cores become chill pins when the mold is filled with iron (left). Clusters of chill pins cast inside the part force those areas to freeze sooner so they are shrinkage-free.


rapidly than a straight wire or bolt. In some cases, a hole is drilled through the center of the area where the spring is located, and in other cases, the spring is machined entirely out. In both cases, the drilled surface must not reveal shrinkage voids of any size. Chills also may be embedded into a


core as it is produced in order to provide chilling of the iron. Te metal chills do not melt into the casting but extract heat more quickly from the shrinkage-prone sections of the casting. Metal chills must have clean, dry surfaces and often are coated with a ceramic wash. In Figures 7 and 8, bolts were formed


as “ram-up” type inserts set into the pat- tern before creating the mold section to accelerate freezing in a green sand mold.


Fig. 6. A metal spring inserted into the core to produce a cylinder head casting serves to provide a high surface chilling device (left). A sectioned cylinder head reveals the remnants of a spring that did not totally melt but fused to the surrounding iron.


7. Produce Uniformly Strong, Rigid Molds


Ductile iron can be produced without


40 | MODERN CASTING February 2013


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