REACTION-MECHANISM BETWEEN ALUMINA GRAPHI TE IMMERSION NOZZLE AND LOW-CARBON STEEL

Reaction between refractory and molten steel causes clogging in the im mersion nozzle in continuous casting process. Reaction mechanism betwe en alumina graphite nozzle containing silica and molten steel was stud ied on the observation of immersion nozzle after casting and the funda mental experiment. The results are summarized as follows, (1)The react ed zone with a lot of pores where contents of SiO2 and C decreased wer e observed in immersion nozzle refractory after casting. (2)The reacti on in refractory was given by the following reaction formula as a whol e. SiO2(s) + C(s) = SiO(g) + CO(g) (3)The overall reactions between Al killed steel and the alumina graphite refractory, and between Ti kill ed steel and the alumina graphite refractory were given by the followi ng reaction formulas respectively, (Al killed steel) : 3SiO2(s)+3C(s)4Al=2Al2O2(S)+3Si+3C (Ti killed steel) low C, high Ti region: 5SiO2(s) +5C(s)+6Ti=2Ti3O5(s)+5Si+5C high C, low Ti region : 5SiO2(s)+5C(s)+3Ti =Ti3O5(s)+5Si+5CO(g) (4)In SiO2-C refractory 50% of SiO2 was evaporate d as SiO and the other 50% changes into SiC by the carbothermic reduct ion of SiO2. On the other hand, in Al2O3-SiO2-C refractory 100% of SiO 2 was evaporated as SiO.