Displacement of the solidified shell of AC4C alloy castings and metal mold was measured simultaneously at the early stage of solidification in a rectangular cast iron mold using linear variable differential transformer. As molten metal was poured into the mold, bending of the mold occurred toward the liquid side immediately because of the temperature gradient along the mold thickness. This temperature gradient in the mold, however, decreased with time. Therefore it appeared that distance between two measuring points at mold surface contracted first, and dilatated thereafter. And it was possible to predict this behavior with simply supported elastic beam theory. It could be identified that mold and casting moved together after pouring until airgap formed by measuring displacement of casting and mold simultaneously. Airgap formation time increased and airgap until final solidification time of casting became smaller with mold preheat temperature.
