PURPOSE: To make suitably variable the amount of crown so as to make possible the forming work corresponding to the rolling condition, in the sleeve type roll with variable crown, by selecting the minimum wall thickness of sleeve, the length of pressured zone of sleeve, etc., being obtained from the formulas.
CONSTITUTION: Correspondingly to the rolling condition (the sectional shape of parent metal, the breadth of sheet, the rolling load, etc.), the minimum wall thickness t min of sleeve, the length l of pressured zone of sleeve, the taper angle α of the wall of sleeve, respectively has to be selected within the limit given by the formulas 1W3 (in which, R is the average radius at the central position of sleeve, D is the external diameter of sleeve, L is the extreme length of sleeve, B is the breadth of steel sheet to be rolled, q is the rolling load per unit breadth, and P is the hydraulic pressure to be applied); unless, the strip with good shape can not be obtained from the rolling. Besides, if the straight zone of taper angle α is to be made a circular arc (radius ρ), the interval between the straight zone of taper angle α and the circular arc curve is made ▵t, and when its maximum value is taken as ▵t max and the maximum wall thickness of sleeve is taken as t max , their relation is settled at ▵t max <0.1t max . Hereby, the forming work corresponding to the rolling condition, which was impossible by the conventional method, becomes possible.