Process for box annealing a steel strip coil

A process for box annealing a steel strip coil, comprising the steps of:

• pretreating a steel strip in such a manner that a side edge portion of said steel strip is subjected to a thermal treatment different from another thermal treatment to which the remaining portion, including an opposite side edge, of said steel strip is subjected, the difference between the thermal treatments applied to said side edge portion and said remaining portion causing the longitudinal length of said edge portion to become different from that of said remaining portion of said steel strip;
• winding said pretreated steel strip under tension to form a coil in such a manner that greater tensile stresses are created in either one of said side edge portion and said remaining portion, which one has a longitudinal length smaller than that of the other one, than those produced in the other one;
• placing said coil on a base plate in such a manner that a side edge included in said portion having the greater stresses, of said steel strip, is brought into contact with said base plate, and;
• box annealing said coil on said base plate in a box annealing furnace.