| 摘要 |
<p>PURPOSE:To obtain a high internal face quality as far as possible by using a mandrel bar equipped with a tapered part connected to a regular part and the rear side thereof, bringing the whole length of the effective part of the mandrel bar into contact with a pipe and moving it according to the roll interval change in the vicinity of the pipe end. CONSTITUTION:The mandrel bar 2 having a regular part 2a and tapered part 2b is used and it is displaced to the upper stream side than the terminal of a roll bite part at the front end of the regular part 2a thereof, in the case of the rolling start. When the front end of the above mentioned regular part 2a reaches the above terminal with the movement being started together with the engagement of the pipe with the roll bite part, it is positioned so that the front end of the pipe reaches the same point simultaneously with it. Simultaneously the movement of the mandrel bar from the initial position is made at the speed decided so that its arrival and that of the pipe rear end to the roll bite part start point may be carried out simultaneously, while until the rear end of the regular part 2a reaches the roll bite part terminal. The no contribution part in the rolling of the pipe does not priority is caused in the thermal load and lubricity and a high internal face quality can be obtained.</p> |
