Obtaining Cast Reinforced Structures by Liquid Phase Combination of System Components

Processy litʹâ, 2020, Tom 139, №1, p.69-75

Abstract

Received 08.02.2020

UDK 621.74.046

Options for obtaining composite cast materials with functional properties are considered. The methods of matrix alloys reinforcement by the reinforcing phase are analyzed. It is proved that the most effective method of formation of materials with special functional properties from nonferrous and iron-carbon alloys is the reinforcement of these alloys at the liguid-phase coupling of system components. In this case, the use of the method of casting on gasified models, reduces the complexity and complexity of operations for the location of the reinforcing phase in the cavity of the form, because it is possible to install it at the stage of model making. The influence of the reinforcing phase on the formation of the structure and properties of cast reinforced structures based on iron carbon alloys has been investigated. Based on the conducted metallographic studies, it was found that upon receipt of cast reinforced structures, where the gray and high-strength cast iron is used as a matrix alloy there is transition (diffusion) zone without a clear interface between heterogeneous metals. The microstructure of the transition layer differs both from the structure of the matrix alloy and from the structure of the reinforcing phase. For example, the intense flow of heat and mass transfer processes in the interaction of pig iron with a partition of Ст3 steel causes a significant melting of the partition, thus forming a large width of the transition zone – 0,15–0,18 mm and there is an intense saturation of the steel with iron carbon and due to the local carbon accumulation of the liquid due to destruction of the model. In the reinforcement of cast iron castings and high strength cast iron with spherical graphite with 2 and 5 mm diameter rods of steel 20, sufficiently deep carbonization and considerable diffusion of carbon from iron into steel is revealed, which depends on the temperature at the contact surface of the liquid and solid phase and solidification speed of the casting. The total value of the diffusion zone (transition zone) is 0.4–0.6 mm. It has been found that the formation of the microstructure and the size of the transition zone are influenced by the chemical composition of the matrix alloy and the reinforcing phase, the temperature of the liquid matrix alloy and the cooling rate of the casting, which is also related to the amount of reinforcement phase introduced.