Effect of pouring system on shrinkage porosity of TiAl alloy rod castings by centrifugal casting

Abstract

Numerical simulation was used to study the influence of the diameter and riser structure of rod castings on the shrinkage porosity of TiAl alloy rod castings by centrifugal casting. The reasons for the influence were analyzed according to the filling and solidification temperature fields. The results indicate that the diameter of rod castings is increased from 16 mm to 20 mm, the diameter of the entrance area is further designed into 20 mm, and the diameter of the distal end is 16 mm, the tendency for blocking the rod casting filler channel is gradually reduced, the temperature of the molten metal for feeding is increased, and the solidification time is gradually increased. Thus the feeding effect is increased, and the level of shrinkage porosity is gradually reduced. Based on the conical design of rod castings, compared with the rod castings without risers, the added ring-shaped riser causes the sequential solidification tendency of the molten metal during filling weakened, the temperature of the molten metal for feeding during solidification decreased, and the solidification time shortened. Thus the feeding effect is decreased, and the level of shrinkage porosity is slightly increased. With adding the cone-shaped riser, the sequential solidification tendency of the molten metal during filling is enhanced, the temperature of the molten metal for feeding during solidification is increased, and the solidification time is increased. Thus the feeding effect is improved, and the level of shrinkage porosity is decreased. The pouring test of the casting is carried out with the best design. The average value of the maximum shrinkage porosity of the section of rod castings is basically the same as that of the simulation test.

Keywords

• TiAl alloy
• centrifugal casting
• rod casting diameter
• riser structure
• shrinkage porosity
• numerical simulation