Abstract
Local corrosion of clay bonded SiC specimen at the liquid iron alloy-slag interface has been investigated at 1550°C in order to elucidate the mechanism of local attack of blast furnace trough material at the slag-metal interface. Results obtained are as follows:
Local corrosion arises in the narrow zone just below the two liquid interface, regardless of partial pressure of oxygen of gas phase and also impurities contained in pig iron and slag. The extent of the corrosion depends on carbon concentration of the metal. The corrosion zone has a thin slag film between the specimen and the metal phase. It is estimated that the slag film plays important roles in the occurrence of the local corrosion because of its vigorous movements which accelerate the mass transfer and the abrasion of the specimen.
This movements are caused by the Marangoni effect and CO bubbles evolved as a product of SiO2 reduction in the film by carbon in the metal. SiC granules on the surface of the specimen are oxidized by iron oxide in the film into carbon granules, which may facilitate the abrasion of the specimen by the turbulence of the film in the case of the metal not saturated with carbon. When the metal is saturated with carbon, the carbon granules remain in the film and may supress the local corrosion.
