| 摘要 |
PURPOSE:To prevent an invasion of air to a fitting part by a simple technique and to improve the productivity of the titled pipe, by providing a glass material to a groove formed at the lapping part of both ends of inner and outer pipe- stock billets, fitted together by hot working, and melt sealing the groove by heating the billets. CONSTITUTION:A groove 4 is formed at an annular lapped part 3 at both ends of an outer pipe stock 1 and a cylindrical or columnar inner pipe stock 2 inserted to the stock 1 in a fitted state. Glass materials of low and high viscosities are provided to the deep part and surface of the groove 4 respectively to melt them by heating 5 the billet A in order to perfectly seal the fitted part without causing the effluence of glass. In this way, the invasion of air is prevented by a simple technique, and the productivity of a tightly contacting double pipe is enhanced.
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