Simulation Research On Casting Process Of SiC Ceramic/K4169 Alloy Composite Casting

In this paper,the composite casting of SiC ceramics/K4169 alloy is taken as the research object.Based on the pouring experiment,the influence of casting process on the flow field,temperature field and stress field in the casting process of SiC ceramics/K4169 alloy composite casting is explored by using the finite element simulation method,so as to optimize the integrated forming process of SiC ceramics/K4169 alloy composite casting.Through the simulation study of SiC ceramic and K4169 alloy composite grid wing castings,the theory of composite component forming is enriched,and the theoretical and practical basis is provided for the practical application of heat-resistant and loadbearing integrated grid structure in aerospace.Based on the finite element method,the multiple physical fields(flow field,temperature field and stress field)in the casting process of SiC ceramic and K4169 alloy composite castings were analyzed.The results show that the surface temperature of SiC ceramics rises to the pouring temperature in a very short time after contact with molten metal,while the temperature inside the SiC ceramics rises relatively slowly,and the temperature distribution inside the ceramics is not uniform.At the beginning of solidification,the temperature at the ceramic end rises sharply and the temperature gradient inside leads to uneven thermal expansion and thermal stress.Then with the homogenization of temperature and the solidification and cooling of the composite casting,the thermal stress begins to decrease.When metal solidification reaches a certain strength,the thermal stress caused by metal solidification shrinkage gradually increases due to the significant difference between ceramic and metal in elastic modulus and thermal expansion coefficient.Finally,there is still a large residual stress in the casting.Five levels were set for casting temperature,casting speed,preheating temperature and intermediate layer thickness to explore the influence of each factor on the casting process.The results show that the pouring speed mainly affects the flow state and pouring time in the cavity.When the pouring speed increases from 0.1m/s to 0.5m/s,a "vortex" appears at the inner gate,the flow rate increases from 0.3m/s to 2m/s,and the filling time decreases from 7s to 1.48 s.The casting temperature has obvious influence on the solidification time and state of the metal part,but has little influence on the thermal stress of the SiC ceramic end in the early solidification stage.Therefore,the casting process of K4169 alloy is mainly considered in the selection of casting temperature.The preheating temperature can avoid the sudden rise of temperature of SiC ceramics and relieve the temperature gradient inside SiC ceramics.The average temperature gradient inside SiC ceramics decreases by about 3?/mm for every rise of preheating temperature of 100?.Therefore,the thermal stress at the ceramic end in the early solidification stage is alleviated obviously.The addition of the intermediate layer alleviates the residual stress of the interface.Through observation of the three areas where stress concentration is easy to occur,the thickness of the intermediate layer with the best effect is 0.2mm.Through the range analysis of the peak residual stress of the casting,the order of the influence of each factor is as follows: preheating temperature > thickness of the intermediate layer >pouring temperature > pouring speed.In this paper,the final process parameters are determined as follows: pouring temperature 1450?,pouring speed 0.2m/s,preheating temperature 1000?,intermediate layer thickness 0.2mm.The SiC ceramic and K4169 alloy composite castings were obtained by investment casting.The composite castings have a complete structure and no obvious defects.