Riser Optimisation Technology Research And Application For Superalloy Casting

Superalloys have excellent high temperature performance compared to conventional alloys under high temperature conditions and are widely used in key parts of aero-engines and gas turbines.The superalloy has a great strategic significance,research on such alloys focuses on the development of new grades,heat treatment process and performance improvement of existing grade alloys.The superalloy castings are mostly thin-walled parts,has a low casting yield and difficult to machining,mostly used for precision castings.Therefore,improving the casting yield of superalloy castings and ensuring the quality of castings can be a research direction,which is of great strategic significance for improving economic benefits and applying it in a wide range.In this reserach,Inconel 939 superalloy is used as the research object,designe the feature model of superalloy casting.The inner and outer ring flange riser size of the feature model is optimized,calculate the riser size by referencing to the modulus method of common carbon steel riser design,and the Latin Hypercube method is used to design experimental scheme,finite element analysis to simulate the experimental scheme,statistical simulation results.Establish response surface model based on different algorithms and select a response surface with smallest error,and a multi-objective optimization model is established based on the response surface,through combine Non-Dominated Sorting Algorithm-II(NSGA-II)and Multi Criteria Decision Maker(MCDM)to find the optimal combination of parameters which match the constraints.Using Pro CAST to simulate the optimal parameter combination,statistically the results,compare the results with the NSGA-II,and prove the reliability of the optimization.The main research contents are as follows: Establish a feature model.According to the common structure of castings,the feature model is designed to replace most casting models,so that the research results have certain generalization,because superalloy is mostly used for aero-engines and gas turbines,these components are generally ring-shaped parts,and has a extremely complicated structure,according to the similarity principle,the model is simplified and the feature parts are added to complete the feature model.Apply the Latin Hypercube method to design experimental scheme.The riser optimization of the feature model,due to there is no related research for the superalloy castings,refer to the riser calculation method of the common carbon steel castings to determine a bigger riser and the size range of the riser.Pro CAST finite element analysis calculation.After the experimental scheme is determined,the finite element analysis is performed,and the boundary conditions are set with reference to the actual casting and solidification process,so that the results obtained by the finite element calculation analysis are closer to the actual results,statistical finite calculation analysis results,prepare for the next step of optimization.Multi-objective optimization software mode FRONTIER performs parameter optimization,NSGA-II algorithm is used for parameter optimization and MCDM is used for multi-criteria decision making.Using the results of finite element analysis calculation to establish response surface model based on different algorithms,and the response surface model with higher precision is selected.After the output constraint is set for the multi-objective response surface model,the NSGA-II optimization algorithm was used for multi-objective optimization.The optimization results use MCDM to choose,and weights are applied to the optimization target to obtain the optimal parameter combination,thereby completing the riser optimization process for the entire superalloy casting.Through the research on the riser optimization technology for superalloy castings,it is found that the casting yield can be further improved,compared with the modulus method from 43.21% to 59.94%,the high-diameter ratio of the superalloy optimized riser is similar to the recommended design of the riser design for steel casting,the results get from finite element calculation and actual casting are closer.Applying this optimization technique for open impeller castings,the results show that the casting yield is increased by 15%.