| 摘要 |
(57) A sheet steel strip which is wound to form lock seam tubing with helical seams has a projecting edge flange (2) along one longitudinal side and a closable channel (11) on the other longitudinal side, which slips onto the edge flange of the last turn during winding. The height (h) of the edge flange (2) is reduced by crease zones (4, 17) in the edge flange (2) and in the free flange (12) of the channel, which are formed by upsetting during closing.
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