A critical review of the role of Mould current in the remelting processes

Until recently, analyses and control strategies of the remelting processes assumed that in the high temperature region the process current is completely contained in the path between the electrode and the ingot. It is now generally recognised that there is also a second path, electrode to mould (‘mould current’), which plays a significant role in both the process heat balance and process parameters, hence influencing the ingot structure. This report critically reviews the published experimental evidence and process analyses relating to the effect. In both the main processes, electroslag remelting and vacuum arc remelting, the mould current plays an important part in establishing ingot structure but in the present process operations it is neither measured nor controlled. It is postulated that further work directed towards control of the mould current is necessary for optimising reproducible ingot quality. It is further concluded that valid computational analyses of the processes must allow for the component of mould current.