and were stiffer and tougher than gravity filled sands at any percent compactibility tested.


• Aeration sand filled specimens showed less test-to-test variability than gravity filled specimens.


Presentation Casting Skin Management in


Compacted Graphite Iron Part I: Effect of Mold Coating and Section Tickness (13-1391)


Authors Sarum Boonbee


and Doru Stefanescu, Te Ohio State Univ., Columbus, Ohio


Background


Recent research demonstrated that shot blasting is a viable solution for the elimination of casting skin and its negative effects on the mechani- cal properties of compacted graphite iron. Researchers explored the effect of section size on skin thickness and


the use of mold coatings to minimize casting skin. Inactive, active and reactive mold coatings were used in experimental compacted graphite irons with carbon equivalent in the range of 4.06 to 4.53.


Conclusions •


Fig. 4. Cone jolt specimens of aeration-filled sand showed no flaw at 35% compactability, while gravity filled sand specimens exhibited cracks.


The thickness of the casting skin increases as the casting section size increases (Fig. 5). • Te performance of the inactive coatings depended on their thermal conductiv- ity. High thermal conductivity coatings increased the skin thickness. • Ferrosilicon was


60 | MODERN CASTING May 2013


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