| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an improved stopper having a structure enabling the use of much less refractory materials without causing strength shortage while maintaining as little use as possible of hand-work. Ž<P>SOLUTION: A refractory stopper integrally formed in substantially cylindrical shape is composed of three portions (A, B, C), wherein a first portion (A) extends from the upper end towards the lower end over a distance greater than a distance (d), a second portion (B) extends from the first portion (A) towards the lower end, and a third portion (C) extends from the second portion (B) and has a stopper nose ending at the lower end of the stopper. The stopper is characterized in that: the second portion (B) has a circular section; the diameter of the average section of the second portion (B) is smaller than the diameter of the section of the first portion (A); and the largest section of the third portion (C) is larger than the smallest section of the second portion (B). Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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