METHOD FOR SUPPRESSING VARIATION OF THICKNESS IN SECONDARY COLD-ROLLING MILL

PROBLEM TO BE SOLVED: To provide a method for suppressing the variation of thickness in a secondary cold-rolling mill by which an off-gage length after a weld point is passed through is more drastically shortened than heretofore. SOLUTION: The secondary cold-rolling mill 6 which is situated on the outlet side of a continuous annealing furnace 4 and with which the rapture of the sheet is prevented by lowering the threading speed of the sheet and also lowering the rolling load at each stand of the secondary cold-rolling mill 6 when a mash seam welding point of the steel sheet is passed through the secondary cold-rolling mill with which a tin-plate system thin steel sheet is heavily reduced at the draft of 7-38%. The function of the rolling speed and rolling reduction at the first stand for every classification of type of steel/size is beforehand set as correction data and the length of the off-gage is made not more than one-tenth that of a conventional method by changing the rolling reduction at the first stand by using the function when acceleration time after the welded point is passed through. COPYRIGHT: (C)2007,JPO&INPIT