Effects of As Cast Holes on Cooling Patterns in Directional Solidification of Plate Castings

Abstract

The directional solidification characteristics and generation patterns of isolated pools of liquid metal in plate castings with as cast holes were numerically examined, and fundamental concepts for the casting design, including the holes, were also investigated. For the as cast hole effects H/T (H: as cast hole effective range, T: plate thickness), there were differences depending on the hole size as well as the casting and mold materials, which reflect the directional solidification characteristics associated with the cooling effects due to the hole. For the finite-width plate castings with as cast holes, isolated liquid pools occurred at locations between a hole and an end face or between the holes under specific conditions. The generation status of isolated liquid pools indicated that the conditions with larger values of the difference between the end and as cast hole effects (E−H)/T (E: end-effective range) in the range of 1.8–5.3 are preferable for preventing the generation of isolated liquid pools. Therefore, the consideration of (E−H)/T is useful for the casting design. In addition, the generation of isolated liquid pools could be prevented by the appropriate use of chills. Moreover, the generation was sometimes prevented by a temperature decrease of the melt during mold filling. The success of these techniques in preventing shrinkage defects was experimentally confirmed.