Study Of Corrosion Mechanism Of Magnesia Chrome Bricks Used In RH Furnace

The influences of adding sesquioxides (Al₂O₃ Cr₂O₃ Fe₂O₃) and ZrO₂ on the properties of magnesia chrome bricks were studied in this paper. The manufacturing process of the magnesia chrome bricks in RH furnace was confirmmed, whose Cr₂O₃ contents were 20% and 25% respectively in rebounded magnesia-chrome bricks. The experiments were carried out separately in immersion nozzles and at the base of vacuum cabin in the RH furnace. An examination was made on the corrosion mechanism of the used bricks by the means of SEM, EDAX, X-rays.The experiment results show that: 1, With the increase of Al₂O₃ and ZrO₂ contents, the high-temperature strength and thermal shock resistance will be increased, while Fe₂O₃ is a harmful component; 2, As the Cr₂O₃ content increases, the thermal shock resistance of the material will be increased, but the density and high-temperature strength of the material will be decreased; 3, The properties of the materials with fused magnesia, synthesized magnesia-chrome clinkers and chrome ore as raw materials at high temperature could be improved significantly by the addition of the ultra-fine ZrO₂ and Cr₂O₃,by increasing the content of Al₂O₃ and Cr₂O₃,by decreasing that of Fe₂O₃. 4,The magnesia chrome bricks were worn mainly in the dissolution of MgO in the molten slags and the penetration of slags into bricks resulting in the peeling of the bricks. The severe dissolution of periclase in acid slag ,the slag penetrating into the bricks along the crack forming a low-melting phase, the alternation of ferrous oxsides resulting in the volume of magnesia chrome bricks change, and the density differences between penetrated layer and brick layer altogether lead to the structural spalling of the magnesia chrome bricks.The fierce erosion of gas-slag-steel and the temperature change in the furnace enhence the structural spallings; 5,The corrosion resistance of spinels to the slags is of great importance to the magnesia chrome bricks. The corrosion resistance of magnesia chrome spinel is the best among them. And therefore it is helpful to improvement of the properties of magnesia chrome bricks to increase magnesia chrome spinel content.