An electric furnace includes a stationary lower shell having a sloping floor extending downwardly to a tap hole to always maintain a sufficient ferrostatic head three times the tap hole for slag free tapping. The configuration of the refractory for containing a heat, is sufficient to maintain a liquid metal heel of at least 70% of the heat before tapping for maintaining flat bath operation during refining a steel melt. An upper furnace shell is supported on the lower furnace shell and a furnace roof is supported by the upper furnace shell. The entire furnace is mounted on a furnace transfer car that is anchored for stationary operation but moved to a furnace exchange position for servicing any of the components making up the furnace. The furnace roof and/or upper furnace shell may be supported at a furnace operate position while the lower furnace shell is transported to the furnace exchange position.