ANALYSIS OF THE FORM AND EVOLUTION OF THE SOLID PHASE DURING DIRECTIONAL CRYSTALLIZATION OF NON-FERROUS METALS WITH ELECTROMAGNETIC INFLUENCE BY ULTRASONIC AND TEMPERATURE METHODS

Abstract

The paper is devoted to the experimental study of new mechanisms of controlling the process of directional crystallization of non-ferrous metals. The focus of the study is on the development and testing of measuring techniques applicable both to laboratory modeling and to processes under real operating conditions. The mechanism of controlling the rate and homogeneity of crystallization of a metal melt by changing the phase angles between the supply currents of a traveling magnetic field induction stirrer is proposed. This makes it possible to generate vortex flows of various topologies in the liquid metal, in particular, to change the number of large-scale vortices or to suppress the large-scale flow. It is shown that the hydrodynamic flows have an impact on the crystallization front shape, which allows one to control the homogeneity of metal solidification by changing the characteristics of the power supply of the inductor. It is important to note that a change in the phase angles of the currents while maintaining the supply amplitude does not significantly affect the crystallization rate, which opens up wide possibilities for controlling processes by changing both the current strength and the phase angles. The temperature method for determining the position of the crystallization front was successfully applied and verified by ultrasonic velocimetry measurements. It has been found that, in the presence of developed flows in a liquid medium, thermocouple measurements provide good agreement (up to a few percent) of the measured position and geometric shape of the crystallization front with the ultrasonic measurement data. In the absence of liquid phase stirring, the difference between the thermocouple and ultrasonic measurements increases slightly. Nevertheless, even in this case, the thermocouple method can be used to correctly determine the position and velocity of the crystallization front.