Testing Magnesia-Carbon Bricks for Oxidation Resistance

Abstract

<p> </p><p><span style="font-family: Times New Roman; font-size: small;">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). </span><span style="font-family: Times New Roman; font-size: small;">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</span><span style="font-family: Times New Roman; font-size: small;">°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.</span></p><p> </p>

Oxidation resistance of magnesia carbon bricks and the influence on their performance

“…The test method for oxidation resistance of magnesia carbon refractories at high temperatures has not yet been defined in ISO, EN or ASTM. In this paper, a test method that has been used for more than 20 years at the Research and Technology Center of the United States Steel Corporation was adopted to evaluate the oxidation resistance of various carbonaceous bricks [26]. The samples were cut into a cubic shape with dimensions of 50 mm × 50 mm × 50 mm and heated in the air environment.…”

Study on the protective effect of the dense slag layer on converter lining

“…[2][3][4] The degraded matrix has significantly increased porosity, making it easily penetrated by slag and steel and sensitive to thermal shock and mechanical punching. [5][6][7] MgO-C refractories used in steelmaking furnace linings also contain very small amounts of calcium and silicon in addition to magnesia and graphitic carbon. At the steelmaking temperature, MgO and SiO 2 react with carbon to form gaseous Mg, SiO, and CO, respectively, which have been discussed by previous authors from the thermodynamic point of view.…”

“…Meanwhile, carbon reduces MgO into gaseous Mg, the reoxidation of which forms a secondary oxidation phase at the reaction interface, that is, dense the MgO layer, to improve the corrosion resistance of the refractory 2–4 . The degraded matrix has significantly increased porosity, making it easily penetrated by slag and steel and sensitive to thermal shock and mechanical punching 5–7 …”