| 摘要 |
<p>PURPOSE:To improve thickness deviation of a welded part and a base material part in the cold drawing of an electric resistance welded tube. CONSTITUTION:Plural roll stands are arranged continuously, three roll stands for stretch reducing are arranged at the interval of 120 deg. in the circular periphery direction round the rolling pass line of each roll stand and the electric resistance welded tube is cold drawn by a 3-roll type stretch reducer wherein rolls at adjacent roll stands are arranged at the interval of 60 deg. to each other in the surface orthogonal to the rolling pass line. The difference of excess metal allowance between the welded part and the base material part generated when the welded part is stretch-reduced is corrected by thickening the smaller part preliminarily before it is stretch-reduced. In this way, since a small diameter and thick wall tube high in the value of a ratio t/D of the wall thickness to the external diameter can be manufactured at a high accuracy of wall thickness and the base tube size can be enlarged, the welding efficiency and the tube making speed can be improved.</p> |
