Mechanism for Local Corrosion of Solid B₂O₃ at Water–Gallium Interface Induced by Branched Flow

抄録

A fundamental study using a water model has been carried out to propose the mechanism for the local corrosion of a refractory near the slag–metal interface in terms of the bulk flow of the slag and liquid metal. The present model consists of water, liquid gallium and solid B₂O₃, whose physical properties have a similar relationship to high-temperature systems. It is found that the local corrosion of the refractory near the water–gallium interface is induced by a branched flow that separates from the main stream of the water. The branched flow is considered to be generated by the interaction between the capillary pressure within a gap near the gallium meniscus and the bulk water pressure. After the branched flow is generated, an eddy occurs near the water–gallium interface, and thus a drag force generated by the water is locally applied to the B₂O₃ surface, resulting in local corrosion. In corrosion tests using water–glycerin solutions, which have the same order of kinematic viscosity as slags at high temperatures, both the branched flow and the local corrosion are observed. The proposed mechanism can be applied to systems in which the slag–metal interfacial tension does not change significantly as well as to systems in which the interfacial tension changes when the refractory dissolves into the slag.

Fig. 9 Schematic diagram of mechanism for local corrosion of B₂O₃. (a) Process by which main stream branches to form two flows and definition of characteristic length in this system, (b) branched flow II generates eddy within the gap formed between the B₂O₃ plate and liquid gallium, which promotes local corrosion efficiently.