Raw materials for manufacturing of Superior quality MgO-C bricks

Abstract

In SAIL Plant, Magnesia carbon (MgO-C) bricks are used as lining material for Metallurgical Vessels like Steel ladles as well as Basic Oxygen Furnaces (BOF). MgO-C bricks are the most suitable refractory in these conditions for slag line as they possess superior slag penetration resistance and excellent thermal shock resistance at elevated temperature. In Iron & Steel Industry, manufacturing processes has changed significantly due to the rising demand of quality steel in the market. Furnace capacities have increased & technological parameters have changed. Plants have been modernized with addition of secondary steel making facilities to meet the stringent quality requirement of newer grades of steel.Refractories in steel ladle are subjected to severe operating conditions like high temperature (1670-1700°C) tapping of liquid steel from BOF, thermal shock, abrasion with molten metal due to stirring during gas purging, localized heating in slag zone due to arcing, corrosion with slag, thermo mechanical stress etc. Hence, use of superior quality refractory material with evenly distributed impurities is essential to get an end product of very high corrosion and spalling resistance and high thermo-mechanical properties. Easier application technique is also required for higher lining life with less down time. Various qualities of magnesia carbon refractories are used in different zones of steel ladles & BOF. Magnesia carbon refractories are essentially constitute of two highly refractory components i.e. magnesia and graphite.Sea water magnesia is mainly used in SAIL as the main raw material for manufacturing of magnesia carbon bricks. Fused magnesia has also been tried by partially mixing with sea water magnesia. Although MgO content in magnesia is important up to a certain level, but the type of impurities and their relative proportions plays vital role in achieving good performance. Besides chemical purity, bulk density and crystal size are considered to be very important properties of magnesia for application in BOF and steel ladles. Beside magnesia, graphite of both indigenous and import sources were used in different occasions. Purity of graphite has been reported to have great influence on slag corrosion resistance and hot properties of magnesia carbon bricks. Particle size distribution of graphite influences porosity and thermal shock resistance properties of magnesia carbon bricks.This paper deals with the properties of different raw materials for making of superior quality MgO-C bricks for improved performance in Metallurgical vessels of SAIL plants.