Multi layer composite pipe can be produced by centrifugal casting. When multi-layer composite pipe or other parts are produced by centrifugal casting, the outer layer material is usually cast first, then the inner layer liquid metal is poured into the mold after the outer layer material has cooled for a period of time, and then the pipe is pulled out after it has completely solidified. When casting the inner material, part of the cooled outer material may be remelted under the action of the higher temperature inner metal liquid, and then solidify together with the inner metal liquid. In this way, there will be a transition region between the inner and outer layers of the casting, which is different from the single-layer casting pipe, so researchers at home and abroad have also studied the solidification process of the multi-layer composite pipe.
Cheng Jun, Jing Tao and others have carried out numerical simulation on the solidification process of composite layer of centrifugal casting composite cast iron roll. On the premise of a large number of assumptions, they have established the mathematical model of the solidification process of composite layer, deduced the finite element format for solving the temperature field of solidification process, developed the finite element program for solving the temperature field of metal mold and composite layer, and discussed the solidification process and heat transfer characteristics of composite layer, Finally, the temperature of the inner surface of the composite layer is measured by the microcomputer infrared temperature measurement system, and the calculated value is in good agreement with the measured value.
Ju and inou studied the temperature field, solidification mode and stress field in the centrifugal casting process of multi-layer shaft roll. They coupled the heat conduction equation, stress / strain equation and Scheil equation, considered heat transfer, heat radiation, inelastic work and latent heat of crystallization in the heat conduction equation, introduced elastic viscoplastic constitutive relation into the stress / strain equation, and solved the equation by finite element method. The effects of material properties and boundary conditions on temperature field and solidification mode were discussed And residual stress.
Wang Yufei, Yang Zhenguo, etc. used ANSYS software to analyze the cooling and solidification process of centrifugal SHS ceramic lined composite pipe. Through the analysis, they obtained the temperature change with time of each layer (outer steel, inner Fe, ceramic) under different thickness of SHS layer and the curve of residual thermal stress with radius after cooling to room temperature. The results show that the ceramic layer and inner Fe layer are subjected to compressive stress, while the outer Fe layer is subjected to tensile stress, and the absolute value of the stress increases with the increase of the thickness of SHS layer. The reasonable adjustment of the thickness of SHS layer can reduce the residual thermal stress at the interface, so as to improve the safety and reliability of ceramic composite pipeline.
Fjeld and ludwigni introduced VOF and enthalpy porous medium method to solve the numerical model in the numerical simulation of centrifugal casting solidification process of industrial grade large composite casting, focusing on the study of the outer material and transition region during casting inner metal.
Liu Jing and Han Jingtao used ANSYS finite element software to simulate and analyze the temperature field of the outer layer and the inner and outer layers during the solidification process of the composite pipe, and determined the casting time interval of the inner and outer layers and the solidification time of the inner melt, which provided a theoretical basis for the actual production.
In addition, some scholars have discussed the determination method of heat transfer coefficient in the solidification process of centrifugal casting.
Cai Yuli et al. Studied the comprehensive heat transfer coefficient of coating air gap in centrifugal casting process. They first determined the thermal conductivity of the coating by the “ball method”, and then gave the calculation formula of the comprehensive heat transfer coefficient of the coating air gap.
In his dissertation, fan xuefan investigated the heat transfer coefficient between casting and mold by using inverse algorithm. First, the temperature time curves of different parts of casting and mold were obtained by experiments. Then, the average value of heat transfer coefficient between molten metal and mold was determined by the inverse calculation module of ProCAST casting engineering finite element analysis software platform. Finally, the surface of mold was investigated The influence mechanism of roughness on the interface heat transfer coefficient.
