STUDY OF THE CAUSES OF BASE METAL MELTING DURING ELECTROSLAG SURFACING AND METHODS OF ITS REGULATION

Abstract

This paper considers the possibility of quickly assessing, both by calculation and experiment, the temperature change for some points located at the same distance from the surface to be deposited, and, accordingly, the change in the depth of penetration of the base metal depending on the location of the strip electrode in the slag bath. The liquid slag bath, having a lower density than the molten metal, is constantly above the surface of the metal melt, protecting it from air. Droplets of filler metal passing through the slag are subjected to metallurgical treatment and are purified from harmful impurities. The direction of slag convection depends on the diameter of the electrode: when surfacing with a thin electrode, forced electromagnetic convection prevails, the slag sinks near the electrode and rises along the edges of the slag pool, while when using a thick electrode, free thermal convection prevails, the slag sinks along the edges of the slag pool and rises near the electrode. As a rule, the technological process of ESR involves minimal mixing of the base metal with the deposited metal. It is very difficult to carry out such surfacing according to the usual classical “vertical surfacing” scheme and at a low surfacing height. A distinctive feature of ESR is that as the depth of electrode immersion in the slag increases, the heat concentration around the electrode increases. In this case, the volumetric density of thermal energy increases, which determines the nature of flows in the slag bath, the depth of penetration of the base metal, and, accordingly, the degree of its mixing with the deposited metal. Therefore, one of the ways to control the effect of slag bath energy parameters on the base metal is to adjust the position of the heat centre in the slag bath. The penetration of the base metal is one of the most important characteristics of any surfacing process, which determines the quality and properties of the deposited metal, as well as the productivity and efficiency of surfacing. Studying the features of the electroslag process using film and photography through a transparent medium made it possible to trace the stages of the electrode melting process, melting of the base metal edges and to record the shape of the metal bath surface.