Study On Steel/aluminum Bimetal Composite Casting Produced With In-mold Induction Heating

The steel/aluminum bimetal castings have been widely used in industry production, which have some good properties such as light, heat-resistant, wear-resistant, and also can endure corroding. The difficulty of the research was that the surface of the steel tube must be highly clean, in order to avoid oxidizing as far as possible, when the steel tube was being preheated. Using the method of induction heating was an extremely ideal choice. By this method, it was very quick to preheat the steel tube, to reduce the surface oxidation, and also to reduce the production cost. Using the foundry process of inlay, the steel/aluminum bimetal compound castings were produced by the fluid solid union way. The research about the relationship between the volumes' rates, the steel tube's preheating temperature, the aluminum alloy's fluid pouring temperature and the induction heating frequency to the bimetal compound castings organization and mechanics performance had been done. The discussion about compound mechanics and crack forming process of steel/aluminum bimetal compound castings and other relation question also had been carried on.The result showed that increased the volumes' rates, enhanced the preheating temperature of the steel tube, enhanced the pouring temperature of the liquid metal as well as the appropriate choice of the induction heating frequency were advantageous to surface fuse and atoms diffuse. Thus enable the contact surface to obtain the metallurgy union. Through microstructure and XRD analysis, the compound level mainly contains FeAl₃ and Fe₂Al₅. Through to coherent surface scanning analysis, the Al atom was very difficult to diffuse to the solid steel, the mainly diffusion process was from the Fe atom to the liquid aluminum. Through to compound castings crack analysis, the crystal structures and the physical performance are different between steel/aluminum. Temperature of the two metals were different when casting. Therefore under the cooling and the coagulation of the liquid aluminum, it would may create very large thermal load as a result of different shrinkage mass, Therefore only through produce and expansion of the crack, the internal stress could dissipate. And also during the process of casting, it might create gas holes because of the air mixing. In the experiment, the preheating temperature of the carbon steel reached 730℃, the fluid pouring temperature of the aluminum alloy reached 750℃, volumes' rates (aluminum alloy compare to carbon steel) was 8:1, under the annealing temperature of 350℃, kept these castings under this temperature about 1 hour. Under this process, cracks were not generated, and the castings with high mechanical performance had been produced.