| 摘要 |
PURPOSE:To obtain the title mold capable of giving cast pieces of good surface properties, enabling continuous casting for a long time, by constructing boron nitride of hexagonal system and silicon nitride in specified proportion. CONSTITUTION:The objective ceramic mold 1 directly fitted on the sidewall 2 of the lower part of a tundish and directly cooled with a water-cooling jacket 3 is constructed from 10-50wt.% of hexagonal boron nitride and the rest of silicon nitride. To manufacture this mold 1, a binder is added to hexagonal boron nitride powder and metallic boron powder followed by kneading the resultant mixture with an organic solvent and then performing granulation, the resultant granular powder being formed. Thence, the resulting form is heated and calcined in a nitrifying gas atmosphere at ca. 1,200-1,600 deg.C followed by machining. In case the amount of the boron nitride is <10wt.%, the heat shock resistance of the mold 1 will be low, being liable to develop cracks at the beginning of casting; while if >50wt.%, the mechanical strength of said mold 1 will decrease due to reduction in the amount of the silicon nitride, therefore, said mold will not be endurable to the incorporation into the jacket 3; furthermore, decrease in the wear resistance will become hard to be drawn for a long time. |
