Reaction Mechanism between Alumina Graphite Immersion Nozzle and Low Carbon Steel

Reaction between refractory and molten steel causes clogging in the immersion nozzle in continuous casting process. Reaction mechanism between alumina graphite nozzle containing silica and molten steel was studied on the observation of immersion nozzle after casting and the fundamental experiment. The results are summarized as follows, (1)The reacted zone with a lot of pores where contents of SiO2 and C decreased were observed in immersion nozzle refractory after casting.(2)The reaction in refractory was given by the following reaction formula as a whole, SiO2(s) + C(s) = SiO(g) + CO(g)(3)The overall reactions between Al killed steel and the alumina graphite refractory, and between Ti killed steel and the alumina graphite refractory were given by the following reaction formulas respectively, (Al killed steel): 3SiO2(s) + 3C(s) + 4Al = 2Al2O3(s)+3Si + 3C(Ti killed steel)low C, high Ti region: 5SiO2(s) + 5C(s) + 6Ti = 2Ti3O5(s) + 5Si + 5Chigh C, low Ti region: 5SiO2(s) + 5C(s) + 3Ti = Ti3O5(s) + 5Si + 5CO(g)(4)In SiO2-C refractory 50% of SiO2 was evaporated as SiO and the other 50% changes into SiC by the carbothermic reduction of SiO2. On the other hand, in Al2O3-SiO2-C refractory 100% of SiO2 was evaporated as SiO.