In this study, a Ti–48 at.% Al–2 at.% Nb–2 at.% Cr alloy was cast by bottom-pouring cold crucible induction melting (CCIM), and the shrinkage depressions formed in ingots during solidification were investigated. Ingots with different heights were produced, and shrinkage depression height and yield were evaluated based on longitudinal cross-sectional observations. The normalized ingot height ranged from 4 to 25, and the shrinkage depression height increased from 20 mm to 105 mm with increasing ingot height. The yield ranged from 77% to 97% and did not increase monotonically, exhibiting noticeable scatter even among ingots with similar heights. The casting rate ranged from 0.025 kg/s to 0.18 kg/s, and the shrinkage depression height increased with increasing casting rate, whereas no clear correlation was observed between the yield and the casting rate. When the nozzle inner diameter ranged from 2 mm to 5 mm, both the shrinkage depression height and the yield increased, accompanied by scatter. The Reynolds number was evaluated as a parameter representing the average flow condition of the pouring stream; however, shrinkage depression formation could not be uniquely explained by the Reynolds number alone, indicating that melt feeding behavior and heat extraction conditions must also be considered.
Nishimura et al. (Tue,) studied this question.