Fused magnesia production technology, product characterization and uses in refractory applications

Magnesite (MgCO3) is natural source for production of caustic calcined, dead burned and fused magnesia. Turkey's magnesite sources have a well-known reputation internationally with high purity, cryptocrystalline structure and suitability for refractory applications. For high temperature processes, there is a great need for refractory raw materials that can withstand oxidative environment at elevated temperatures. Fused magnesia (FM) is the most important material for these purposes with melting point 2800 °C and one of the key element of the refractory heat resistant materials especially for steelmaking refractory bricks. Fused magnesia is considered to be one of the best thermal and electrical insulators with high density, high purity and large crystals. Fused magnesia (FM) is produced by electric arc melting of caustic calcined magnesia (CCM) in a traditional Higgins furnace at >2800°C. Quality of the electrically fused magnesia is determined by choosing magnesite source, beneficiation processes, arc furnace electrical parameters and sorting. Final product were characterized by using chemical analysis, bulk density measurement, optical and scanning electron microscope and EDX and XRD. Samples from different initial materials and ingot zones were investigated according to their crystal size, bulk density and impurity formation. It was shown that the main factors in obtaining high quality fused periclase are the purity of the raw materials, determining the high MgO concentration in periclase; occurance of impurity transfer into the skin of the ingots. The specification of columnar and center crystals of fused magnesia ingots derived from the present study can give high performance in magnesia-carbon bricks and subsequently longer campaign life for better converter and electric arc furnace hot spots/slag line applications.