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 SiO
2 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,
SiO
2(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): 3SiO
2(s) + 3C(s) + 4Al = 2Al
2O
3(s)+3Si + 3C
(Ti killed steel)
low C, high Ti region: 5SiO
2(s) + 5C(s) + 6Ti = 2Ti
3O
5(s) + 5Si + 5C
high C, low Ti region: 5SiO
2(s) + 5C(s) + 3Ti = Ti
3O
5(s) + 5Si + 5CO(g)
(4)In SiO
2-C refractory 50% of SiO
2 was evaporated as SiO and the other 50% changes into SiC by the carbothermic reduction of SiO
2. On the other hand, in Al
2O
3-SiO
2-C refractory 100% of SiO
2 was evaporated as SiO.
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