| 摘要 |
PURPOSE: To easily increase the crushing strength of an UOE steel tube used for submarine line pipe, etc. CONSTITUTION: A steel plate is worked into tubular state by means of U press and 0 press, welded, and subjected to tube expansion, by which the steel tube is produced. At this time, the steel tube after tube expansion is heated up to 150-<700 deg.C so that the heating index represented by (absolute temp.)×(5+log(time)) becomes 1300-<4300. By this method, the Bauschinger effect can be reduced or removed by means of a simple heating device while obviating the necessity of the alteration of equipment on a large scale, and the UOE steel tube increased in crushing strength can be provided.
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