| 摘要 |
<p>Steel tubes with large dia. are produced by (a) descaling the tube, pref. by >90%, (b) a heat-treatment comprising a progressive local heating of the steel tube from one end to the other in axial direction and quick cooling, and (c) widening the tube, e.g. by mechanical or hydraulic means. Tubes can be used as pipelines for natural gas and petroleum. Tubes have high accuracy of shape, tenacity and tensile stress. Heat-treatment comprises the quick and local heating of the tube to a temp. between the Ar3-transformation point and the temp. at which coarsening of the austenite grains sets in, and strong cooling to quench the tube.</p> |
