| 简介 |
PROBLEM TO BE SOLVED : To form a neck part having reduced crystal defects in a relatively short time and to control, for example, a mechanical defect caused by thermal stress by temperature distribution.SOLUTION : In a first growing step for forming a neck part 2, a growing chamber 16 is filled with a first rare gas or a mixed gas comprising the first rare gas and a second rare gas whose thermal conductivity is smaller than that of the first rare gas. In a second growing step for forming a shoulder part 4, the growing chamber 16 is filled with a mixed gas comprising the first rare gas and the second rare gas. In a third growing step for forming a direct barrel part 6, the growing chamber 16 is filled with a mixed gas comprising the first rare gas and the second rare gas or the second rare gas. The concentration (%) of the second rare gas in the second growing step is made larger than the concentration (%) of the second rare gas in the first growing step, and the concentration (%) of the second rare gas in the third growing step is made larger than the concentration (%) of the second rare gas in the second growing process. |
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