Research On The Centrifugal Casting Numerical Simulation Of Titanium Impeller

In this paper, titanium alloy impellers as the investigated object, the fillingregularity and solidification characteristics of complex thin-walled castings areinvestigated during the process of the centrifugal casting. The filling state andlocations, the solidification sequence and the formation rules of the castingdefects are also investigated under the different technology parameters andtechnology program by theory analysis, numerical simulation and experimentsresearch.The filling and solidification process of the complex thin-walled castingsprepared by the centrifugal casting are studied using numerical simulationmethods. The studies show: Under the effect of the centrifugal field, the alloymelt firstly fills the runner wall along the opposite direction of rotation of thecast. When the melt reaches the mold, it fills the area with a lager centrifugalradius. Then the distribution characteristics of the temperature field, flow fieldand pressure field, the solid fraction and the solidification time are studied forthe alloy melt under the centrifugal condition. The studies show: In the fillingand solidification process of alloy melt, the guiding role of the centrifugal fieldmakes the local location of the casting be the active region for the heat and masstransfer. It reflects in the large fluctuating temperature, the higher disorders ofthe liquid flow and the delay of solidification time and so on, resulting in thechanges of the casting solidification order foe local area, which provides thebasis for analyzing the formation of casting defects.And the effects of different casting technological parameter on the fillingand solidification order for the titanium-alloy melt are studied using numericalsimulation methods. The technological parameters include centrifugal speed,mold preheat temperature, the degree of superheat of the alloy melt, the amountof pouring alloy melt. Simulation results show that: under a certain centrifugalradius and centrifugal casting system, the filling position and the morphology foethe alloy melt change with the increasing of the speed of the rotation. Theincrease of the shell mold preheat temperature and the temperature of pouringmolten alloy will delay the solidification time for the blades while the effect ofincreasing the preheat temperature of the shell mold is more obvious. Thetemperature of pouring TC4alloy impeller is not too high, because a hightemperature does not improve effectively solidification status and the tendency toform shrinkage shrinkage increases. Too much amount of the alloy melt willcause the change of the temperature field during the later filling process. Under the centrifugal field, the filling state of alloy melt has a significant effect on thetemperature of the alloy. In the later filling process, the reduction of the Coriolisforce causes a change of the filling force field along the filling direction, whichcauses the change of the temperature of the melt, even causes the remelting forsome solidification area which has a significant impact on the formation ofdefects. The semi-enclosed-open system which Meet sprue runner cross-sectionalarea greater than the cross-sectional area, cross-sectional area larger than therunner cross-sectional area of the runner-open gating system design, the runnerdesign and casting into a small contact cylindrical aspect ratio, increasing thefillet, additional casting end with tiled stable melt filling protection.To verify the correctness and accuracy of the simulation results and thetheoretical analysis, the titanium impeller is prepared by centrifugal casting.Comparing the simulation results and the experimental results, it can beconcluded that the difference of solidification for the local areas of blade isdetermined by the filling position and degree of the disorder. The formationmechanism of the shrinkage porosity and cold shut is investigated and therelevant solutions are also found. To achieve a smooth and tiled filling the orderis to achieve alloy solidification: The s the experimental results correspond to thesimulation results.