| 摘要 |
PURPOSE:To decrease the influence of a non-metallic inclusion in a molten steel by maintaining the prompt hole openability of the titled structure obtd. by using particles consisting essentially of silica as a packing material for an upper layer and particles consisting essentially of carbonate of alkaline earth metal as a packing material for a lower layer. CONSTITUTION:Particles consisting essentially of carbonate of alkaline earth metal are used as a packing material for a lower layer with respect to a packing material for an upper layer of a sliding hole composed of particles conssiting essentially of silica. Then the packing material for the lower layer is easily decomposed to generate gaseous carbon dioxide when heated by a molten steel; at the same time, the packing material falls immediately on account of shrinkage of the particles themselves. The virtrified packing material for the upper layer remaining by virtrification is easily broken by the head pressure of the molten steel by which a hole is instantaneously opened. Since the packing material for the upper layer is vitrified in this case, the material falls in the form of a relatively large lump into the molten steel and floats easily on the molten steel owing to a difference in specific gravity. The floating material is absorbed in the slag layer on the surface of the molten metal without forming a harmful non-metallic inclusion. |
