Intensive riser cooling of castings after solidification

A new method - post solidification intensive riser cooling (PSIRC) was proposed. Risers are cooled by forced air or water mist from its top surface as the solidification of a casting finishes, then the risers are turned into cooling passages during the cooling process of a casting with contrast to their function of feeding passages during the solidification process. This method can realize inside-out, fast and even cooling of castings, which may improve the production efficiency and reduce residual stress and deformation. A forced air cooling system with close-loop control for PSIRC was designed and developed. The temperature difference between the typical thick and thin locations of a casting was fed back to control the cooling intensity. The PSIRC method was applied to the casting process of a stress frame specimen and a hydro turbine blade. The effect of PSIRC on the cooling of the castings was investigated. The cooling speed of these castings increased apparently with improved temperature distribution uniformity. One day was saved for the blade casting before shakeout. The PSIRC method improved the strength and hardness of the blade casting, and significantly reduced its residual stress meanwhile.