| 摘要 |
PURPOSE:To prevent the deterioration of cast slab quality by forming the specific thickness range from a nozzle inner surface by refractory composition having the prescribed grain size and also adding still unstable zirconia aggregate having the prescribed grain size at the specific ratio. CONSTITUTION:The layer 2 of refractory composition having <= 0.15 mm grain size and at least >= 2 mm thickness thereof is formed on a part or whole of inner face of a submerged nozzle body 1, and also still unstable zirconia aggregate having 0.3-1.0 mm grain size is added at 1-5% ratio. By arranging the layer 2 of refractory composition having such a grain size composition, the initial roughness RA of inner face of nozzle can be formed to <= 3.5. Further, as the unstable zirconia aggregate in which no CaO and MgO is entered into solid solution, the local wear in the inner face of nozzle is restricted and good roughness is maintained. Therefore, the deterioration of cast slab quality caused by peeling and mixing, etc., of the inclusion is prevented. |
