Measurement of the expansion force and mold wall movement during solidification in spheroidal graphite iron castings was attempted using a force gauge and infrared displacement meter. Different casting molds were made with five different modulus varying from 1.0 to 4.5cm by the furan sand process. Quarts bar was used as the sensor for each mold. The cooling curve during solidification was measured at the same time. The results showed that the solidification pressure increased when the modulus increased, and it was saturated at the modulus of 3.0cm. The maximum pressure was about 5 MPa. On the other hand, the displacement was also found to increase without saturation as the mold wall movement increased when the modulus increased. The quantity of free carbon, which is the most effective factor for solidification expansion, has been already been clarified to not differ among castings with different modulus in the authors' former study. It is thought that the different expansion pressure is caused by graphite formation mechanism, and this causes castings to shrink more at a smaller modulus.
