| 摘要 |
<p>Conventional expander heads cannot be used when steel tubes have to be expanded and calibrated which have a helical longitudinal welded seam, because the groove in the head is for straight seams and would have to be different for every tube size with helical seams. The segments of the expander head are lined therefore with a layer of elastomer material, vulcanized to steel sheets, to a thickness of two to five-times the height of the internal weld bulge. The pref. material is a polyurethane elastomer of 70-100 Shore A hardness. Such an expander can be used to expand and calibrate tubes, independent of the pitch of the welded seams.</p> |
