Abstract
Critical length and diameter of riser neck experimentally determined by G. Sciama for a cylindrical sand casting of three different alloys were successfully reproduced by numerical solidification simulation. As shown by Sciama, the critical diameter is dependent on the neck length and on the cast alloy. Numerical simulation indicated the presence of a critical neck length below which directional solidification is realized with a neck of a minimum diameter. Effects of riser size, casting size and superheat were also examined. A more or less reasonable neck size can also be obtained by conventional design rules. But there is a room for further effort by pursuing the optimum size.
