Дослідження процесу формування біметалевих виливків дробильно-розмельного обладнання

Abstract

The analysis of the state of production of wear-resistant materials showed that one of the promising directions for improving their quality is the use of bimetallic castings, which have a complex of properties differentiated by the volume and surfaces of the products. However, the problem of obtaining a high-quality connection of the base and the working layer has not been solved until now. The article examines the influence of the chemical composition, temperature parameters, and mass ratio of alloys of bimetallic pairs on the process of bimetallic castings formation. The purpose of the study was to study the growth kinetics and structural-phase composition of the transition diffusion layers of bimetallic castings depending on the chemical composition, temperature parameters and the ratio of the masses of the alloys of the bimetallic pairs. As a research result, it was established that the formation of transition layers of bimetallic castings is determined by the processes of diffusion and structural-phase transformations in the interaction zone - "solid - liquid metal". The processes largely depends on the chemical composition of bimetallic pairs, temperature parameters, and the mass ratio of the layers. It was determined that in bimetallic castings obtained by pouring liquid metal onto a preheated solid billet, the transition layer is characterized by the presence of two zones - pearlitic, from the side of the base metal and without the carbide region of the matrix of the working layer. It has been established that the formation of transition layers in bimetallic castings obtained by successive pouring of melts into the mold through autonomous pouring systems is accompanied by the saturation of steel by carbon from cast iron to a depth of 600-800 microns and the formation of a zone with a lamellar pearlite structure along the border of the alloy junction, and the transition layer between cast iron and steel consists of pearlite in the form of a narrow strip and a zone of chromic ferrite from the side of cast iron. As a result of the study of the peculiarities of the formation of transitional layers of bimetallic castings when liquid metal is poured onto a solid billet, it was established that the degree of dissolution of the base metal in liquid cast iron increases with an increase of the billet preheating temperature and the temperature of the melt, as well as the ratio of the mass of liquid cast iron to a unit surface area of the metal base. At the same time, the rate of dissolution is proportional to the gradient between the temperatures of the contact surface and the cast iron solidus. It was established that the formation of a reliable diffusion bond for bimetallic pairs "carbon (low-alloy) steel - high-chromium cast iron" is ensured if the temperature of the contact surface exceeds the temperature of the eutectic transformation of cast iron. The mechanism is revealed of formation of the transition zone structure. The materials of the article can be used by scientists for further research and practitioners in the selection of materials for work in extreme conditions. Keywords: steel, cast iron, temperature, transitional layer, solidus, liquidus, melt, solidification.