| 摘要 |
In an outer tube, which is made of silicon carbide, and which has an upper portion closed and a lower portion opened, has the lower portion formed with a tapered portion so as to expand a diameter thereof toward a lower end thereof, and has a flange formed on an outer peripheral side of the lower portion; the following conditions are met: 1) a ratio of ta/D1 is from 0.0067 to 0.025, 2) a product of taxD1 is from 600 to 4,000 (mm<2>), 3) (DF2-DF1)xtc/(D1xta) is from 0.1 to 0.7, and 4) L1/L2 is from 1 to 10; where the outer tube has a thickness of ta (mm) and an inner diameter of D1 (mm), the flange has a thickness of tc (mm), an inner diameter of DF1 (mm) and an outer diameter of DF2 (mm), and the tapered portion has a height L1 (mm) and an expanse of L2 (mm).
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