Electroslag remelting of steel and alloys for turbine rotors - using alkaline earth metal to deoxidise fluorspar contg. slag to obtain very low aluminium content

摘要

During the melting process the slag, which contains CaF2, is deoxidised by aluminium which is partly or completely replaced by one or more alkaline earth metals. The deoxid. of the slag is pref. undertaken by Ca; or by Mg and/or Ba which may be added as fluorides. Several alkaline earth metals may be used where one is Ca; and the metals are pref. placed in a metal sheath for addn. to the slag. The alkaline earth metals may also form a core in a tubular steel wire driven by a wire feeding machine into the slag. When Al is used for oxidising the slag, the resulting steel contains Ca. 0.02% Al, which is detrimental in some steels, e.g. it can reduce the creep resistance of turbine rotors used in power station plant. The invention reduces the Al content to 0.01% without impairing other properties.