Construction of AC Electric Arc Furnace     

The furnace consists of a steel shell, lined with suitable refractory materials and is mounted on the tilting mechanism. The shell thickness is around 0.005 times the shell diameter. Three electrodes enter through the roof. The hood may be swung away for charging. Heat is generated by the hot area formed between the electrodes and the charge.

Hearth

The hearth contains metal and slag. The hearth lining consists of backing lining and working lining. The backing lining is few layers of high fired magnesite bricks on which working lining is rammed with either dolomite or magnesite mass. Permeable blocks or porous refractory elements are introduced through the bottom to inject inert gas for stirring. The EAF steel bath is shallow; the aspect ratio of the bath is around 0.2 to 0.22.

Roof

The roof is exposed to more heat than other furnace elements. Its lining is also subjected to radiant heat reflected from the walls and slag. High alumina bricks and magnesite – chromite bricks are used for roof lining. The roof lining is water cooled which increases the life of refractory lining to at least 10-20 times more than without water cooling.

The roof has three holes to allow insertion of the electrodes.

Electrode

A typical alternating current operated EAF has three electrodes. Electrodes are round in section, and typically in segments with threaded coupling, so that as the electrodes wear, new segments can be added. Graphite electrodes are preferred over carbon electrodes because of better electrical conductivity. The electrodes are automatically raised and lowered by a positioning system.