Research on Material and Technology of Centrifugal Casting Composite Roll

Centrifugal casting is a traditional casting method, which is mainly divided into horizontal centrifugal casting and vertical centrifugal casting according to the process. Because of its unique technological characteristics – hollow parts can be obtained without setting the core, and the metal parts obtained are compact in structure, with few pores and inclusions, centrifugal casting has been widely used in functionally gradient composites and wear-resistant materials such as bimetallic and metal-based ceramic composite pipe fittings. In addition, on the basis of the traditional casting, a new process has also been derived, such as electromagnetic centrifugal method. At the same time, in order to comprehensively and deeply analyze the mechanism, centrifugal casting technology has been involved in the research of computer simulation, defect control, and accurate calculation of centrifugal speed.

Composite material is generally a multifunctional material composed of one material as the matrix and another or more materials as the reinforcement. These two or more materials can complement each other in functions, such as metal matrix ceramic composite, bimetallic composite, functional gradient composite, etc. Among them, functionally gradient composite is a new type of composite, which is characterized by changes in composition or microstructure in a specific direction. The research shows that centrifugal casting is the simplest and most efficient method to prepare some functionally gradient composites at present. The main advantage of centrifugal casting to prepare functionally gradient composites is that it can make the casting have good filling property and control the composition gradient caused by the centrifugal force and the density difference between materials. Zhang Jian et al. summarized the preparation process of functionally gradient composites in detail, and pointed out that centrifugal casting has the advantages of simple equipment, high production efficiency, batch production, low cost, high density and large size functionally gradient composites. Chen Jia et al. carried out quantitative research on centrifugally cast aluminum-based functionally gradient materials (self-generated Mg2Si/Si particles), and found that the larger the diameter of the part, the higher the volume fraction of the reinforcing particles at the same position from the inner wall of the mold, and the volume fraction of the particles from the inner wall to the outer wall first increased and then decreased. The results show that the distribution of particles with different sizes in centrifugal casting composites has certain rules. From the inner wall to the outer wall, the average particle size of primary Si particles is decreasing, while the average particle size of primary Mg2Si particles is increasing.

Song Yanpei et al. prepared the composite structure roll ring by centrifugal casting, and used the high density of WC particles to form the WCp-Fe/C composite working layer and cheap strong and tough core material, in order to achieve the purpose of greatly reducing costs and improving the service life of parts, and obtained the WC particle reinforced metal matrix composite roll ring with impact toughness of 5~6 J/cm2 and composite layer hardness of 63HRC~65HRC. During the composite process of WC particles with the matrix, the surface of the particles is partially dissolved, and fine rod-shaped WC crystals are precipitated in the matrix near the WC particles, and the matrix far from the WC particles is alloyed, and compound carbides of W, Mo, Cr and other elements are precipitated. Han Jianning et al. prepared the particle-reinforced semi-steel roller ring by using different particle adding methods. By comparing the three methods of furnace adding, ladle adding and flow adding, it was found that the centrifugal casting method with furnace adding has the highest particle yield and particle dispersion distribution, and the most obvious reinforcement effect on the semi-steel substrate. The hardness of the matrix before the addition of particles is 45HSD, and the average hardness of the matrix after the addition is increased to more than 55HSD, and the wear resistance of the roller ring is significantly improved. Song et al. prepared WC particle reinforced ferrous matrix composite roller ring by centrifugal casting method. The thickness of the outer composite layer reached 20~45 nm. WC particles were evenly distributed in the outer layer, with a volume fraction of 60%~80%. There was an obvious interface between the ceramic particles and the matrix and no reaction products were observed. The outer strength of the roll ring reaches 80HRA~85HRA, the core reaches 73HRA~76HRA, and the impact toughness is 8 J/cm2. According to the test, under the same working condition, the abrasive wear performance of the composite roll ring is 20 times that of the high-speed steel roll ring, the service life is 9 times that of the high-speed steel roll ring, and the cost is reduced by 50%.