Method of changing rolling schedule during rolling in tandem rolling mill

DETAILED DESCRIPTION The present invention provides a method of changing a rolling schedule during the rolling of a work strip having a gauge change point in a tandem rolling mill including a plurality of roll stands without stopping the rolling mill, wherein roll speeds on the roll stands are changed when the gauge change point of the work strip arrives at any one of the plurality of roll stands, to form a roll speed pattern fulfilling the conditions for maintaining the steady-state mass flow constant and for minimizing the total sum of changes in roll speed on the plurality of roll stands on the basis of a function expressing a total amount of changes in roll speed.
Preferably, the conditions for maintaining the steady-state mass flow constant may be fulfilled so that, each time the gauge change point of the work strip arrives at any one of the roll stands, roll speeds on all the roll stands are uniformly changed so as to minimize a total amount of the changes in roll speed.
Then, roll speeds on the roll stands including the roll stand at which the gauge change point arrives and disposed upstream of the last-mentioned roll stand are changed to speed ratios according to a new rolling schedule while roll speeds on the roll stands including the abovementioned any one of the roll stands which are disposed downstream thereof are kept to speed ratios according to the original rolling schedule.
Conveniently, the roll speed pattern may be formed by using the sum of the squares of ratios of change in the roll speed on the plurality of the roll stands as a minimizing estimation function.