For high power and ultra high power electric arc furnace, which’s smelting condition is more severe, high grade refractories such as corundum castable, corundum precast block, chrome corundum castable, chrome corundum block, corundum magnesia castable and corundum magnesia precast block are mainly used at electrodes triangle zone of EAF cover. Burned high alumina bricks or unburned high alumina bricks, magnesia bricks and magnesia chrome bricks are usually used at outer parts of furnace cover.
Factors affecting EAF cover service life include equipment, operation, product quality and so on. For equipment aspect, Main factors influencing EAF cover’s service life are:
Electric arc furnace steel making is ultra high power, which greatly enhanced electric arc optical intensity and thermal radiation strength, the temperature of furnace cover is increased, which will increase thermal shock and sintering shrinkage of furnace cover refractory materials, cause increase of thermal stress and sintering stress, intensifies structural spalling. What’s more, ultra high power smelting also lead to increase of dust, which will accelerate the corrosion to furnace lid refractory material.
Furnace cover water cooling area. In order to solve the problem of furnace cover refractory materials’ low service life, the larger furnace cover water cooling area is, the longer service life is, water cooling area is above 70% now. Water cooling method decreases furnace cover refractories using quantity and surface temperature, thus, significantly prolongs refractory material service life. At places near by electrodes holes, where is not convenient for water cooling, high grade refractory materials should be used. To reduce graphite electrodes consumption and increase triangle zone refractory material service life, graphite electrodes can be cooled by sprayed water, and will get significant effect.
For operation aspect, main factor affecting furnace cover service life is furnace cover opening and closing times, i.e., materials feeding times. If furnace cover is more frequently opened and closed, thermal shock times will be increased, refractory materials spalling will be severe, the service life of furnace cover refractory material will be shorter. Other factors such as smelting temperature, smelting time, oxygen blowing intensity all have great influence on furnace cover service life. So furnace lid refractory materials should have good thermal shock resistance, high refractoriness and dust corrosion resistance.
