In order to extend the appiicability of a coupled reaction model to the hot metal dephosphorization process, evaluation method for unknownparameters was investigated. The following points were clarified.(1 ) Mass transfer coefficient in metal phase was increased in proportion to~~/ ' The quantitative information of the influences of various factors on the mass transfer coefficient in the metal and the slag phase, decarburization rate and equilibrium partition ratio are necessary to solve these equations. By these method, Eqs. (6) and (7) were obtained and In Fig. 4

Reaction between refractory and molten steel causes clogging in the immersion nozzle in continuous casting process. Reaction mechanismbetweenthe silica-containing alumina graphite nozzle and the molten steel was studied on the observation of the used immersion nozzle and the basic experiments. The results are summarized as follows.( 1) The used immersion nozzle refractory reveals a reacted zone where the SiO. and C contents are reduced and there are many pores.( 2) The overall reaction in the refractory can be arranged as Si02(s) +C(s) =SiO(g) +CO(g) With the Si02-C refractory containing no Al20.. 50"/. of Si02 is reduced by the C to the SiO gas, and the remaining 500/0 is reduced by the C to SiC. On the other hand, with the AI.O.-Si02-C refractory.all of SiO. is reduced to the SiO gas.

Ja pan.Steel Institute of Japan, It is necessary to clarify the reoxidation factors and quahtitatively determine the contribution of each factor to the reoxidation of the molten steel to prevent the cOntamination in the tundish. In this study, the molten steel in tundish has beensampled in production scale experiment and from the composition changeof the molten steel the amount of reoxidation of the molten steel teemed from the first ladle into an actual tundish has been quantified by factor contents of the molten steel at the tundish inlet remained practically constant and approximately agreed with

No abstract

Basic experiments were conducted on the adhesion of Al 2 O 3 in molten steel when molten FeO is present in the molten steel. It was found that the adhesion and coalescence of Al 2 O 3 particles are promoted when molten FeO is present in the molten steel, that FeO and FeAl 2 O 4 are observed in the bond between the Al 2 O 3 particles, and that this observed result agrees with the pattern of Al 2 O 3 adhesion to the continuous caster nozzle when the molten steel is reoxidized. Based on these experimental results, a study was made of the mechanism whereby Al 2 O 3 adheres to the continuous caster nozzle when the molten steel is reoxidized. When the oxygen concentration in the molten steel is locally raised by the reoxidation of the molten steel, the adhesion force of the Al 2 O 3 particles due to the liquid bridge force of the molten FeO is far greater than the adhesion force of the Al 2 O 3 particles due to the van der Waals force or the surface tension of the molten steel. The adhesion of Al 2 O 3 to the nozzle interface is thus considered to proceed mainly with the molten FeO serving as binder. Since the molten FeO binder changes into a solid bridge of FeAl 2 O 4 in a short time, the Al 2 O 3 particles adhering to the nozzle interface are considered to integrate to form a network of Al 2 O 3 particles faster than possible with solid-phase sintering.