| 摘要 |
PURPOSE: A welding method is provided to have excellent welding intensity and to prevent the inner diameter of a welding unit from reducing. CONSTITUTION: A method is for welding a dummy tube into a quartz glass tube for light fiber basic material. Before, welding the dummy tube into the quartz glass tube, the edge of diameter inner end of the dummy tube and/or the quarts glass tube is cut and then welded by melting with heat. In here, only end part having a smaller inner diameter than the other's is cut for reducing the number of processes when the inner diameter difference between both tubes is more than 20% of the thickness of the tube having a smaller inner diameter. The edge is cut in less than 30% of a tube of which the thickness is more than 2mm. Also, for the edge cut of the glass tube, a C shaped edge cut is used.
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