Distribution of Chromium in Transition Layer of Bimetallic Castings

ENG: The constantly increasing requirements for machine components and mechanisms operating under conditions of impact and abrasive wear determine promising use of bimetallic cast parts. Their quality significantly depends on both the technological factors of manufacture and the properties of the transition layer between the base and the working layer. The aim of the work was to study the influence of the casting mass, the ratio of the mass of the steel base and the working layer of cast iron and the difference in the chromium content in the layers, the pouring temperature of steel and cast iron on the quality of the casting. Research was carried out on bimetallic castings of steel 25L – cast iron 300Kh12G5 and steel 70GL – cast iron ChKh22. The mathematical model of the influence of selected parameters on the width of the chromium transition zone from cast iron to steel and the average rate of chromium concentration change in the transition layer was developed. It was established that the most effective influence on this zone and the rate of chromium change is exerted by the mass and temperature of the steel base, the contribution of which is 67.7% and 60.2%, respectively. It was shown that the width of this zone decreases with increasing difference in the chromium content in the matrix of the working layer and the base and expands with increasing the pouring temperature and mass of steel and cast iron. It was determined that increasing the pouring temperature and the mass of the steel base and the working layer leads to a decrease and the chromium content in the matrix of the working layer and the base to an increase in the average rate of the change of the chromium concentration in the transition layer. These data are useful for optimizing the technology of obtaining high-quality bimetallic castings.