Numerical Simulation Of Solidification And Stress For A K435 Superalloy Blade And Optimization Of Casting Process

The 3rd-stage turbine blades of the gas turbine with the high temperature alloy K435 are studied by numerical simulation method.The researching contents include shrinkage and deformation caused by the stress during the process of solidification,which is tested frequently in production.The relation between the deformation and the stress caused by solidification are studied and the cooling process and the reason why shrinkage appears in the thick part of the blade are also studied.The researching results show that the new process is able to reduce the distortion of the blade caused by the stress and the shrinkage in the blade.The forming of hot tearing were discussed,which doesn't appear frequently as the deformations in production.Based on 3D solid modeling of the blade using UG software to model,the meshcast is discussed to model the mold shell and the asbestos insulation layer.The work of building the model is performed,which is important to the simulation.The material database of allow K435 is built in Procast.Using the equivalent treatment,the material database of mold shell is also built.According to the composition of the alloy K435,the CALPHAD software Jmatpro is used to calculate the performance parameters,which Combined with the data from actual measurement and other reference,there for those ensured the Analysis results accuracy in simulation.The cooling process of the casting solidification is divided into three models.To acquire the boundary conditions of each cooling model,temperature measuring experiment is designed.And by the way of trial and error method,the boundary conditions approaching to the producing process are obtained.The technology of the blade producing is simplified into numeric calculation,which Include initial conditions of the simulation.With the help of simulation calculation of the solidification process of the blade,the characteristics of blade's solidification process are analyzed.The results show that the solidification rate of thin positions is faster than that of thick ones,which vacuum makes solidification rate reduce and mushy zone increase,cause the shrinkage porosity.And it concludes that the different thickness of blade structure leads to different solidification time,which causes that the different parts of the blade enter the elastic state at different times.It's the reason why blade bends towards back.Analyzing the regions whose hot tearing tendency are different,the paper proposes that the region ofcasting whose solidification fraction is more than 90% are likely to cause hot tearing under the action of greater tensile stress.According the reason of blade deformation concluded,the paper designs the new technology of thickening the asbestos insulation layer to reducing the distortion of the blade and the shrinkage.