DEVICE FOR CONTROLLING POSITION OF WORK ROLL AND METHOD THEREOF

PROBLEM TO BE SOLVED: To carry out stable rolling, to remarkably improve capacity and quality by calculating the positional change in the reducing direction due to shifting work rolls and correcting draft positions from the calculated positional change in the reducing direction. SOLUTION: The change ΔS of the gap between the work rolls is calculated by the formula in accordance with the positional change ΔHS (mm) in the rolling direction due to shifting the work rolls 1, which is outputted from a commanding part of position control in the rolling direction of work roll, by the calculating means (gap change arithmetic part) of the positional change of work roll in accordance with the positional change of the work rolls in the rolling direction. Where, in the formula, Dw is the diameter (mm) of the work roll, Di is the diameter (mm) of a back-up roll 2 in contact with the work roll and HS0 is the initial value (lock-on value) (mm) of the offset position in the rolling direction of the work roll. The change ΔS based on the arithmetic result is received by a change correction control commanding part, correcting command is sent to a draft position controller and the draft positions of the work rolls 1 are corrected.