Research On Shrinkage Cavity And Shrinkage Porosity Prediction Of Ti Alloy In Vertical Centrifugal Investment Casting

With good mechanical properties, together with high strength-to-weight ratio and high temperature creep resistance, titanium alloys become more and more popular in the astronavigation and navigation now. Most titanium alloy castings are produced by vertical centrifugal casting. Shrinkage void and porosity are the main reasons to produce waste products, then the prediction of shrinkage void and porosity of titanium alloy casting under the vertical centrifugal casting is the main problem to be solved urgently.A semiquantitative prediction model of shrinkage porosity for titanium alloy castings has been established. As well as the regularity of shrinkage porosity formation under the vertical centrifugal casting condition has been achieved. Real shrinkage volume of casting was calculated according to liquid and solidification shrinkage, which was basing on the temperature computation and by using extent associated method to search isolation.Basting on the generation condition of shrinkage porosity, with the nucleation and growth model of structure simulation, micro void in the shrinkage porosity has been simulated in this paper, as well as the a semiquantitative prediction model of shrinkage porosity under the vertical centrifugal condition has been established. Concept of critical feeding of solid fraction has been amended, and new concept of dynamic critical feeding of solid fraction under the vertical centrifugal condition was introduced. The technology parameters, such as rotational velocity, pouring temperature, mould temperature and rotational radius are the main factors that influence the formation of shrinkage porosity under the vertical centrifugal conditions. Numerical simulation of the experimental casting has been carried out in this paper, and the simulation results show that the volume and distribution of shrinkage porosity decreases with the increase of rotational velocity, the mould temperature and the pouring temperature. It also can be learned from the simulation results that the volume and distribution of porosity decrease with increasing rotational radius.The experimental casting was carried out in this paper, which were used to study the formation regulation of shrinkage porosity. The material used in the experiment was Ti6Al4V and the rotational velocities were 0rpm, 160rpm and 280rpm individually. The dimension and distribution of shrinkage porosity under gravity casting and vertical centrifugal casting has been investigated and the comparison between the experimental and the numerical results shows good agreement, which can be used to prove the correction of established model and the regulation investigated in this paper, as well as it play an important role on the scientific research and practical capacity.