The mechanical properties such as impact initiation, bending strength, macro and micro hardness of the composites under the bimetal liquid lost foam casting process are studied, and the microstructure and morphological structure of the strong layer materials, wear-resistant layer materials and their bonding interfaces are analyzed, so as to provide a theoretical basis for the design of high chromium cast iron and carbon steel composites and guide the actual production.
- the as cast structure of high chromium cast iron is mainly martensite and retained austenite. The austenitizing temperature during destabilization heat treatment is determined according to cr/c. After heat treatment, chromium and carbon precipitate in the form of secondary carbides, and austenite transforms into martensite.
- the wetting of liquid carbon steel on the surface of high chromium cast iron provides conditions for the nucleation of its composite interface. The poured liquid carbon steel reproduces the random wavy surface of high chromium cast iron, making the composite interface present a dog tooth staggered shape; The microstructure of the interface transition region is dense, without obvious shrinkage cavity and loose casting defects, and is in a good metallurgical bonding state.
- the mass transfer model in the transition region is established and the diffusion equation is solved. The theoretical calculation is consistent with the scanning results of the electron microscope: the content of Cr decreases from the high chromium cast iron layer to the carbon steel layer, and the Fe element has a small fluctuation. In the interface bonding area, Cr atoms diffuse from the high chromium cast iron to the surface of the carbon steel layer, and the distribution law is the tiller attenuation curve.
- the time interval of composite pouring is the most critical process parameter to determine the interface quality of high chromium cast iron / carbon steel composites. When the time interval of composite casting is too short (60s), the solid and liquid phases of the high chromium cast iron injected first coexist, forming the opposite of the two materials to obtain the steel and iron coagulation structure; When the time interval of compound injection is too long (90s), the solid phase of high chromium cast iron injected first acts as a strong chill on the heat transfer boundary, and it is difficult to form a global and high-quality metallurgical bonding at the composite interface; According to the test results of microstructure, composite interface thickness and initial impact strength, the most suitable time interval for composite reinjection is about 75s, and the metallurgical bonding between the two metal materials is of high quality, sufficient strength and thickness.
- the relevant mechanical property parameters of the bimetal composite samples have been greatly improved. The Rockwell hardness of the high grid cast iron layer has reached 61hrc, the impact toughness has reached 16.5j/cm2, and the bending strength has reached 1600mpa.