1994 Volume 34 Issue 10 Pages 802-809
Reaction between refractory and molten steel causes clogging in the immersion nozzle in continuous casting process. Reaction mechanism between the silica-containing alumina graphite nozzle and the molten steel was studied on the observation of the used immersion nozzle and the basic experments. The results are summarized as follows,
(1) The used immersion nozzle refractory reveals a reacted zone where the SiO2 and C contents are reduced and there are many pores.
(2) The overall reaction in the refractory can be arranged as SiO2 (s)+C (s)=SiO (g)+CO (g)
(3) The reactions of the refractory with the Al-killed molten steel and the Ti-killed molten steel are given by the following equations:
(Al-killed steel) 3SiO2(s)+3C(s)+4Al=2Al2O3(s)+3Si+3C (Ti-killed steel)
low C and high Ti region 5SiO2(s)+5C(s)+6Ti=2Ti3O5(s)+5Si+5C high C and low Ti region 5SiO2(s)+5C(s)+3Ti=Ti3O5(s)+5Si+5CO (g) (4) With the SiO2-C refractory containing no Al2O3, 50% of SiO2 is reduced by the C to the SiO gas, and the remaining 50% is reduced by the C to SiC. On the other hand, with the Al2O3-SiO2-C refractory, all of SiO2 is reduced to the SiO gas.