薄壁框型钛合金铸件熔模铸造数值模拟及验证

Numerical Simulation and Verification of Investment Casting for Thin-walled Frame Titanium Alloy Castings

薄壁框架类钛合金铸件是铸造领域复杂结构件之一,被广泛应用于航空、航天领域的高端装备重要部件中,对尺寸及形位公差要求严格。由于框架类铸件结构复杂、壁薄且厚度不均,在铸造过程中很容易出现缩孔、变形等缺陷,因此在确定铸造工艺时需要多方面考虑,并通过铸造模拟软件评价工艺的可行性。针对薄壁框型架大体积、大厚壁比、结构复杂,铸造过程易出现缩松缩孔、热裂、变形等的问题,设计顶注式和底注式两种浇注系统方案,采用ProCAST铸造仿真数值模拟软件对两种浇注充型凝固过程温度场、应力场模拟,分析了铸造凝固过程中框型件总缩松率、残余应力、残余变形情况,确定了底注充型方案的可行性,经过对比分析发现,底注式浇注生产的钛合金框型架,相比于顶注式浇注充型过程更加平稳,总缩松率较小,铸件本体肋板及壁板之间的有效应力明显降低,总变形量降低到0.5 mm以下,且变形主要集中于冒口及冒口所在平面。结果表明,底注加冒口工艺有效解决了铸件热节缩孔问题,铸件成形质量、冶金质量和尺寸控制达到预期效果,同时运用铸造仿真模拟技术可有效指导实际铸造过程,缩短试制周期,降低生产成本。

Thin-wall frame titanium alloy castings are complex structural parts in the field of casting and are widely used in important parts of high-end equipment in the aviation and aerospace fields.There are widespread assembly requirements,and strict tolerances in terms of size,shape and position are needed.Owing to the complex structure,thin wall and uneven thickness of frame castings,shrinkage holes,deformation and other defects easily form during the casting process.Therefore,when determining the casting process,it is necessary to consider various factors and evaluate the feasibility of the process through casting simulation software.In this work,to address the issues of the large volume,large thickness ratio and complex structure of thin-walled frames,which are prone to casting defects such as shrinkage and porosity,thermal cracking and deformation during casting,two casting system schemes,namely,the top casting type and bottom casting type,were designed,and ProCAST simulation software was used to simulate the thermal field and stress field during the solidification process of two kinds of casting mold filling.The total shrinkage rate,residual stress and residual deformation of the frame parts in the casting solidification process were analysed,and the feasibility of the bottom filling pattern scheme was determined.A comparative analysis of the simulation results reveals that the titanium alloy frame produced by bottom casting is more stable than that produced by top casting,the total shrinkage rate is lower,and the effective stress between the rib plate and the wall plate of the casting body is significantly lower.The total deformation is reduced to less than 0.5 mm,and the deformation is mainly concentrated in the riser and the plane where the riser is located.The test results show that the process can effectively solve the problem of hot shrinkage holes in casting,and the forming quality,metallurgical quality and size control of the casting can achieve the expected effects.Moreover,computer casting simulation technology can effectively guide the actual casting process,shorten the trial production cycle,reduce the production cost,and provide a reference for high-quality near-net investment casting of thin-wall frame titanium alloy castings.