Investigation In Chrome-free Refractories For Secondary Refining

The composition and structure of the low-carbon MgO-C refractories and the factors affect the properties of the low-carbon MgO-C refractories were discussed as well as the development and problems of the low-carbon MgO-C refractories. The effects of the components on properties in room temperature and high temperature of the low-carbon MgO-C refractories were studied systemically and the slag corrosion resistance of the material was also analyzed. The conclusions were described as follows.(1) As the graphite content increasing, the cold crushing strength, cold modulus of rupture and bulk density of the low-carbon MgO-C refractories are decreased. Meanwhile, The apparent porosity of the specimens with 5% addition of graphite is higher than that of specimens with 3% addition of graphite. The apparent porosity is increased obviously no matter to the unfired or to the fired specimens when graphite content is higher than 5%, which will bring the slag resistance of low-carbon MgO-C refractories down sharply.(2) The oxidation resistance of low carbon MgO-C materials can be increased by adding aluminum powder. However, excessive aluminum powder would lead to pulverization and expanding. So 3% addition of aluminum powder in low carbon MgO-C materials is suitable. Furthermore, the oxidation resistance of low carbon MgO-C materials can be increased by adding magnesium aluminum alloy powder also, which is better than that of adding into the same quantity of aluminum powder. The low carbon MgO-C materials perform the best oxidation resistance with the 0.5% addition of magnesium aluminum alloy powder in mixing adding.(3) The apparent porosity of the specimens fired in air and buried with charcoal is increased and the bulk density of the specimens is decreased with the more addition of MgO-C. When addition of MgO-C exceedes 3%, the apparent porosity is higher rapidly and the bulk density is lower sharply. The suitable addition of MgO-C is 3%.(4) The thermal shock resistance about low carbon MgO-C materials can be increased by changing the addition and adding way of carbon Microsphere, superfine graphite and binder of Carbores.