Patent ID: 8365563

Claim:
Method for flattening steel strip by cold rolling said strip by passing it through at least two cold rolling mill stands each having work rolls, wherein a first of said at least two mill stands has said work rolls having local rigidity K significantly different from a second of said at least two mill stands, wherein the local rigidity K is calculated in Kgf/mm/mm accordance with the equation K = 1 c 8 ⁡ [ ln ⁡ ( 2 ⁢ D Δ ⁢ ⁢ h + cp ) - cp Δ ⁢ ⁢ h + cp ] where K—work roll local rigidity (Kgf/mm/mm) p—roll force per unit strip width (Kgf/mm) u—local work roll flattening (mm) D—work roll diameter (mm) E—work roll elastic modulus (Kgf/mm 2 ) u—poisson's ratio Δh—local draft of the strip (mm) where u = c 8 ⁢ p ⁢ ⁢ ln ⁡ ( 2 ⁢ D Δ ⁢ ⁢ h + cp ) and where c = 16 ⁢ ( 1 - υ 2 ) π ⁢ ⁢ E and wherein the local rigidity K represents the capability of a work roll to resist local flattening.