Numerical Simulation of Bubble Migration in Liquid Titanium Alloy Melt During Vertical Centrifugal Casting Process

The bubble migration in liquid titanium alloy melt during vertical centrifugal casting process has been predicted. The effects of different parameters, such as the initial bubble location, the mold rotational speed and the mold rotational direction on the bubble in the migration process are investigated. The results show that the bubble migration can be divided into the radial movement to the mould rotation axis and the circular movement to the mould wall opposite to rotational direction of the casting mould. The casting mould wall has an impeditive effect on the circular movement of the bubble during its migration process. And the bubble finally migrates like a straight line along the mould wall located at the opposite direction of the rotational casting mould whether it rotates clockwise or anti-clockwise. The bubbles at the position near the mould wall located at the opposite direction of the rotational casting mould are much easier to migrate in a straight line. The instantaneous speed of the gas bubble increases with the increment of the mould rotational speed. However the mould rotational speed is high or low, the moving speed of the gas bubble increases slightly at the primary stage, and then decreases gradually like a ladder.

Melt flow,solidification structures,and defects in 316 L steel strips produced by vertical centrifugal casting

Vertical centrifugal casting can significantly enhance the filling capability of molten metals,enabling the production of complex thin-walled castings at near-rapid cooling rates.In this study,the melt flow,solidification structures,and defects in 316 L steel cast strips with a geometry of 80 mm×60 mm×2.5 mm produced by vertical centrifugal casting were numerically and experimentally analyzed under different rotation speeds.With gradually increasing the rotation speed from 150 r/min to 900 r/min,the simulated results showed the shortest filling time and minimum porosity volume in the cast strip at a rotation speed of 600 r/min.Since a strong turbulent flow was generated by the rotation of the mold cavity during the filling process,experimental results showed that a“non-dendritic”structure was obtained in 316 L cast strip when centrifugal force was involved,whereas the typical dendritic structure was observed in the reference sample without rotation.Most areas of the cast strip exhibited one-dimensional cooling,but three-sided cooling appeared near the side of the cast strip.Moreover,the pores and cracks in the 316 L strips were detected by computed tomography scanning and analyzed with the corresponding numerical simulations.Results indicated the existence of an optimal rotational speed for producing cast strips with minimal casting defects.This study provides a better understanding of the filling and solidification processes of strips produced by vertical centrifugal casting.