| 摘要 |
<p>PURPOSE:To restrain the wall thicknesses in the peripheral direction at tube ends from being ununiform. CONSTITUTION:A hydraulic rolling-down mechanism to control a roll gap through the simultaneous and equivalent symmetrical movement by upper and lower rolls to the pass line is provided on a specific stand of a stretch reducing mill composed of plural stands furnished with caliber rolls and the caliber rolls are got by a hydraulic rolling down mechanism under draft control to thin the wall thickness in a tapered state from the central part toward the tube end so that enlargement of wall thickness at the tube end part generated by a sinking mill of the succeeding stage is canceled when the tube is bitten in and when it is passed through. The rolling reduction of an object stand of draft control at the preceeding stage is set by adding an amount of loss of the wall thickness of a caliber roll flange part generated by draft control of the object stand of draft control at the succeeding stage. In this way, the crop loss due to the wall thickness failure in the peripheral direction at both ends of a seamless steel tube is reduced and the yield of the product is improved.</p> |
