Effect of electromagnetic forces on flow of slag at the surface of a consumable electrode in the electroslag process

摘要

According to the results of experimental investigations, a specific contour of the flow of the slag melt is established in the slag pool in the quasi-stationary electroslag process. For example, when remelting a circular aluminium electrode in a quartz cylinder, positioned on a graphite base (slag is a transparent eutectic mixture KCl +LiCl), a circular flow directed downwards below the electrode and upwards along the solidification mould walls was observed. The possibility of this flow is also confirmed by theoretical analysis carried out in Ref. 2. This case corresponds to the condition rot f_e<0 (f_e is the density of the electromagnetic force). Cases of the opposite direction of the flow of the slag in the vicinity of the electrode are well known. For example, a circular flow of the slag melt was recorded in a current-conducting solidification mould made of a corrosion-resisting steel with a transparent wall. In this case, the flow of the electrolyte in the central part is directed from the metallic bath to the electrode. In Ref. 4, this discrepancy is explained by the fact that in the first case experiments were carried out with a solidification mould with no electrical conductivity, whereas an electrically conducting mould was used in the second case. The variation of the path of passage of current results in a change in the direction of flow of the slag. In these and other similar investigations, the problem of physical reasons for a specific direction of rotation of the slag has not been investigated. On the other hand, the distribution of the electromagnetic forces affect he field of velocities of the slag melt and, in particular, determines the conditions of formation of the field of velocities in the film of metal and the droplet flowing downwards. The hydrodynamic structure of the droplet affects the shape of the solidification front.