Method for identifying thrust counterforce working point positions and method for rolling rolled material

A method for identifying thrust counterforce working point positions in a rolling mill including a plurality of rolls that include a first set of rolls comprising a pair of work rolls and a second set of rolls comprising a pair of backup rolls supporting the pair of work rolls, the method comprising:

• a first step of causing thrust forces at a plurality of levels to act between the plurality of rolls with an unchanged kiss roll load by changing at least either friction coefficients between plurality of rolls or inter-roll cross angles between the plurality of rolls, and at each of the plurality of levels, measuring thrust counterforces in a roll-axis direction acting on the first set of rolls and measuring backup roll counterforces acting in a vertical direction on the pair of backup rolls at reduction support positions in a kiss roll state in which the plurality of rolls are brought into contact by a pressing-down device;
• and
• a second step of identifying, based on the measured thrust counterforces and backup roll counterforces acting on the plurality of rolls, thrust counterforce working point positions of thrust counterforces acting on the pair of backup rolls, using first equilibrium conditional expressions relating to forces acting on the plurality of rolls and second equilibrium conditional expressions relating to moments produced in the plurality of rolls.