Bottom Pouring Vacuum Suction Casting Technology Of TiAl Alloy Connecting Rod

TiAl based alloys have got a lot of attention since being introduced to the industrial sector for their excellent performance, and they are considered as the next generation high-temperature and light alloys to study and application. TiAl based alloys have low ductility and bad cold-forming property ,so it is inevitable to research the casting methods for forming TiAl based alloys.In this particle we research the features of forming connecting rod of TiAl alloy by"in-situ melting and suction casting", and determine the casting process for connecting rod as : using metal mold; vertical mold parting; top gating systerm with a feeder head and askim riser at the bottom; the machining allowance of TiAl connecting rod casting is in the range of 0.5-2mm; the taper angle of TiAl connecting rod casting is 3°.The casting process design of TiAl connecting rod is verified and optimized by numerically simulated the mold filling and solidification process using ProCAST software. By ProCAST software, the filling process, solidification process, and shrinkage porosity formation during suction casting are simulated. The influences of some key parameters on the filling process and shrinkage porosity defect are systematically investigated, including suction hole diameter, pouring temperature, pouring velocity. Especially, the pouring temperature and suction hole diameter make the greater impact. The higher the pouring temperature is more conducive to the filling, but it will increase the contraction of liquid metal when the casting temperature is too high, which is prone to form the shrinkage. Larger diameter suction is conducive to a complete filling, but it makes a negative impact for the melting when it is too large. The optimized processing parameters map for suction casting of TiAl connecting rod is obtained, which could be the guide for the suction casting of TiAl connecting rod. Analysis shows that When the suction diameter of 4mm, the filling speed of 1m/s, the pouring temperature can either less than 1600℃makes the die cavity filling ratio up to 100%.Hot-working die steels 3Cr2W8V is used to make the suction casting mold of the connecting rod, and we improve the mold by summering up the problem of the suction casting process of TiAl alloy rod. One plan makes the mold core activities, through this we study the impact of metallic core and sand core for forming the connecting rod, the metallic core causes a great internal stress in the connecting rod , and the sand core results in the casting shrinkage, porosity and other defects. The other plan integrates the suction casting process and the investment casting process, then we prepare the rod shell and form the connecting rod.Through the analysis results of the microstructure of the connecting rod, we measure the hardness of the rods which are formed by different methods. In addition, the tensile properties of the suction sheet-shaped piece of the Ti47Al2Cr2Nb alloy has been measured, experiments show its room temperature ductility and the tensile strength are greatly improved after homogenization heat treatment.