New tension control at the head of strip in hot strip finishing mill

In this paper, a new tension control scheme is proposed to diminish the width shrinkage at the head of the strip in the hot strip finishing mill. The proposed control scheme is applied before the looper control starts and is composed of three main parts. First, the correlation between the width shrinkage and the current difference of the main motors is analyzed. Second, the tension is calculated from the current difference between the two neighboring stands. Third, the speed of the main motor is controlled by the speed difference between the output of PI controller and the reference speed. It is shown through the field test of the Kwangyang no. 1 hot strip mill of POSCO that the width shrinkage is greatly decreased by the proposed control scheme.