Dissolution behavior of zirconia-refractories during continuous casting of steel

Dissolution behavior of ZrO2-graphite refractories used in a submerged entry nozzle (SEN) during continuous casting of steel was investigated using the rotating cylinder method. In the present work, the dissolution rate of the zirconia-graphite rod was determined by measuring the corrosion depth of the rod after a given immersion time. It was found that the dissolution rate was slow at the surface where molten flux alone is contacted, but much higher at the region that contacts the interface of the molten flux and liquid metal. The dissolution rate was influenced by the rotation speed of the rod, ZrO2 content in the refractories, and the presence of Na2O and fluoride (F−) in the mold flux. It is speculated that a cyclic process wherein zirconia dissolves into the molten flux and graphite dissolves into the liquid metal accelerates the dissolution at the flux-metal interface.