Chimney Structure of Hollow Sand Mold for Casting Solidification

Abstract

The hollow sand mold can affect the cooling of the casting during the solidification process. A chimney structure of a hollow sand mold that mainly consists of a two-layer shell with through channels was proposed. The design method was proposed for the chimney structure. Due to the chimney effect, cool air can enter the chimney from the bottom entrance, and hot air flows out from its top opening. Air transfers heat from the sand mold and forms a temperature gradient from bottom to top. A hollow sand mold with a chimney structure was applied to the wedge plate casting. During the solidification process, natural cooling and forced air cooling through open channels were applied. The effects of the chimney on the microstructure, mechanical properties, and residual stress of the castings under these two different cooling conditions were analyzed and compared with those of the casting in a dense mold. During the solidification stage of the castings, the chimney structure prolonged their solidification time. After solidification, the chimney structure under forced air condition increased the cooling rate of the castings by 61% and the temperature gradient along the vertical direction by a factor of three. The Si content in the Al matrix increased by 20.4%, and the tensile strength increased by 32.66%.