| 摘要 |
Tubes are often reduced in cross-section - generally at the end - in such a way that there is no residual internal space at that point. Common to all the forming methods is that, however great the reduction of the external cross-section, there is still a small residual space. This may be so small that it is invisible. This axial residual space is sufficient for gases or liquids in the interior of the tube to escape via this residual space. In order to prevent this, a material, the melting point of which is lower than the relatively high temperature, arising during deformation, of the tube to be formed, is, according to the invention, introduced into the tube section to be deformed immediately prior to forming. This section of material melts when touched by the tube during forming and remains in the liquid state in the residual space. After forming, the material solidifies and forms the pressure-tight closure.
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