Testing magnesia-carbon bricks for oxidation resistance

Abstract

MgO-C based refractory materials are used in steel metallurgy to a large extent. Magnesia-carbon bricks are tested for basic physical-mechanical parameters in as supplied state, for carbon content, and chemical analysis of magnesium component. According to the type of their usage, they are subjected to tests at higher temperatures, carbonization firing, and after firing, the physical-mechanical parameters are determined at specified temperatures. One of the most tested properties of these materials is their resistance to oxidation. The methodology for such testing is not yet defined in ISO, EN and ASTM test procedures, therefore the methodology used in other countries is being applied. In conditions of U. S. Steel, Košice, s.r.o., the MgO-C bricks intended for the working lining of slag zones of steel ladles are tested by oxidation resistance test (oxidizing area procedure). The described test method was developed at U. S. Steel Research and Technology Center in Munhall and has been used for more than 15 years to evaluate various carbon containing bricks. Test specimens in the shape of a cube are heated in an oxidizing atmosphere to a temperature of 1482°C with holding time of 5 hours. After cutting of the test specimens, the percentage of oxidized area is calculated. This test is used for selecting the appropriate type of lining material for the working lining of slag zone of the steel ladle in the steelmaking secondary metallurgy process and for the building of database of different types of MgO-C bricks.