Method of rolling railroad-rails and steels of similar shape by universal rolling

A method for multiple pass rolling of blanks into shapes having unequally thick flanges, one of said flanges being a base flange and another of said flanges being a head flange, said head flange being thicker than said base flange, in a universal rolling mill comprising a pair of horizontal rolls and a pair of vertical rolls, said universal rolling mill performing precise repetitive rolling in the same rolling stand, making said universal rolling possible with less number of stands having a conventional screw down mechanism, compensating vertical roll-set-up inaccuracy because of the horizontal roll axial displacement during rolling due to the imbalance of vertical-roll forces, even under the rolling condition of uniform longitudinal elongation generally meant for minimizing bending of a blank, said imbalance of vertical roll forces caused by the unequal contact area of the flange width and unequal deformation resistance resulting from the non-uniform temperature of the unequal flange thickness;

• said method comprising the steps of:
• determining axial displacement of said horizontal rolls and radial displacement of vertical rolls based upon a reduction schedule when said blank passes through a specific roll pass surrounded by said horizontal and vertical rolls;
• analyzing the displacements in terms of roll force so as to determine the non-linear relationship between the axial displacement of horizontal rolls and the roll-force difference acting on each of the two vertical rolls;
• setting the base flange roll gap for each pass to correspond to the base flange outgoing thickness minus the base flange vertical roll mill spring minus the corresponding axial displacement of the horizontal rolls;
• and
• setting the head flange roll gap for each pass to correspond to the head flange outgoing thickness minus the head flange vertical roll mill spring plus the corresponding axial displacement of the horizontal rolls, said base and head flange vertical roll mill springs being determined in accordance with the base and head vertical roll force, respectively, divided by the base and head vertical roll mill modulus, respectively, and said corresponding axial displacement being determined by said non-linear relationship using a predicted difference of said two vertical roll forces;
• and
• repeatedly passing said blank through said universal rolling mill with the successive roll gaps set for each pass of the multiple-pass roll schedule in accordance with said setting steps, thereby allowing actual multiple precise rolling of the universal rolling mill without any augmenting roll stand.