The bimetallic liquid lost foam composite casting technology is adopted to carry out the process sample by winding the iron first and then the steel, and inject the bimetallic liner wear-resistant casting. The lost foam belongs to negative pressure vacuum full mold casting. The carbon rich reducing atmosphere in the cavity can avoid the generation of oxides around the cast iron first and avoid the defects of the composite interface of traditional casting in principle. Therefore, according to the key points of the project, the following problems need to be solved:
1) Ordinary white cast iron, nickel hard cast iron and high chromium cast iron are three generations of white cast iron inherited and developed in turn. Compared with ordinary cast iron, high chromium cast iron has been greatly improved in initial resistance, high temperature strength, heat resistance and wear resistance. It is known as the best wear-resistant material in modern times and is widely used. The working conditions of wet ball mill in beneficiation industry are extremely complex, which also puts forward higher requirements for high chromium cast iron, which is required to have the comprehensive properties of wear resistance, impact resistance and corrosion resistance. In response to these requirements, alloying elements or modifiers are added to improve the microstructure and further improve the service properties of high chromium cast iron.
2) Solidification forming of bimetallic liner is an affinity process between temperature field and stress field. Heat transfer directly determines the feasibility of compound casting; The physical parameters of the two materials vary widely with temperature, and the stress is produced at the interface of carbon steel and high chromium cast iron due to temperature shrinkage. Therefore, it is necessary to theoretically reveal the coupling process of heat and stress in the solidification process of carbon steel and high chromium cast iron bimetallic materials, so as to provide a valuable reference for guiding the subsequent lining plate forming process.
3) Since the lost foam casting technology is proposed for the first time to produce bimetallic liner, we must demonstrate the theoretical feasibility of the process in combination with the principle of lost foam casting, and analyze the operability of the process in practice from the bimetallic liquid composite injection process, By optimizing the bimetallic liquid lost foam casting compound casting process, the scientific and technical problems in the production process of bimetallic lining plate are eliminated.
4) Microstructure composition and morphology distribution determine the mechanical properties and working properties of materials, while forming process and heat treatment process directly determine the composition and distribution of microstructure. For bimetallic liquid lost foam casting composite casting and destabilization heat treatment process, it is necessary to analyze the process adaptability of high chromium cast iron and carbon steel through microstructure, The process adaptability of the composite of the two materials should also be discussed. In the traditional liquid-solid composite process, because the interface is in the boundary area of heat source, the interfacial bonding strength of the two metals only depends on mechanical adhesion. Can the bimetallic liquid lost foam casting process realize the metallurgical bonding of the two metals? What kind of thermodynamic conditions and chemical composition can obtain the best characteristic composite interface in the solidification process? We need to return to the above problems according to the research results of microstructure.
5) For the bimetallic composite casting lining plate, the condition of the middle joint surface has a very important impact on the service life of the village plate. If the quality of the intermediate joint surface is poor and no metallurgical joint is formed, the lining plate will break and fall off during use, affecting the service life of the lining plate and even causing accidents. The interface bonding strength must be tested through various mechanical properties to verify the rationality of process parameters.
6) The wear-resistant testing machine in the laboratory is mostly used for the performance test of wear-resistant lining materials. Considering that the load conditions of the wear-resistant testing machine are still very different from the service conditions in the real ball mill, it is necessary to truly reflect the performance of bimetallic lining plate and the advantages of lost foam casting dual liquid composite casting process, The wear resistance test of lining plate must be carried out under actual working conditions.