Investigation of MgAl2O4 formation and sintering behaviour of neutral linings for induction furnaces

Alumina (Al2O3) is one of the most preferred material for neutral induction furnace linings in steel industry due to its high melting temperature, high strength, high hardness and high wear resistance which are very important for refractory applications. In induction furnace applications, chemical durability, thermal shock resistance and mechanical strength of Al2O3 based neutral linings can be improved by addition of spinel (MgAl2O4) or addition MgO to form an in situ spinel phase. For in situ spinel forming alumina based neutral linings, it is also critical to control spinel formation kinetics, distribution of the spinel phase in the microstructure, and sintering kinetics of Al2O3-MgO system. Accordingly, the research objective of this study was to define MgAl2O4 formation behaviour and sintering behaviour of alumina based Al2O3-MgO type of induction furnace lining materials as a function of the particle size of raw materials, sintering temperature, sintering time. For this objective simple four different stoichiometric compositions were prepared with two different particle size of Al2O3-MgO components. The spinel formation and sintering mechanisms of this compositions were investigated at the temperature range between 1350-1700°C. At temperatures 1550, 1650 and 1750°C the spinel formation and sintering behavior of compositions were investigated for 1, 2, 3, and 4 hours holding time. The technological objective of the study was to improve performance of alumina based neutral ramming mass for induction furnaces and to control their properties according to requirements of application. For this objective a neutral ramming and its spinel formation and and sintering behaviour was investigated at 1250, 1450 and 1700°C. Sintering behaviour and spinel formation behavior of standart composition is compared with new composition which were defined as a function of particle size of components, amount of components and amount of impurities