Delta (one – piece roof of arc furnace) is the famous name of the refractory piece of the electric arc furnace (EAF) which is usually manufactured of refractory casting materials and its performance life is very important in production speed. Its internal holes, is the passage location of graphite electrodes of the electric arc furnace. The Saba Zob Sepahan Co. based on the plan of the furnace delta has the capability to manufacture types of delta in various sizes and weights. The refractory materials used in the electric arc furnace delta is usually composed of low cement inclusions and occasionally combined with chromate and inclusions with particular properties.