| 摘要 |
<p>PURPOSE:To uniformize the wall thickness distribution in the axial direction of a product tube by controlling the timing of draft control for grooved rolls in an object stand of control by setting a passing timing of an tube end through the upstream side stand as a standard. CONSTITUTION:In the case that 6th and 7th stands, for example, of a mandrel mill consisting of 8 stands are control objects, timings at which the tube top end is bitten by those stands and other stands and the rear tube end releases from those stands are detected. A roll gap of a grooved roll 6 of the 6th, 7th stands is previously set to a prescribed gap amount for rolling the tube center part. As for the 6th stand, a control output is made to open a roll gap and to set the gap to equal to a gap for rolling the tube center after a prescribed elapse period of time from a biting time when the tube top end passes through a 5th stand. Also as for the 7th stand, a control output is made to narrow a roll gap after a prescribed elapse period of time from the biting time when the tube top end passes through the 6th stand. Thus, the timing control for roll gaps is performed so that the roll gap amounts are controlled to be equal.</p> |
