Method for increasing the range of production of a metal product rolling installation and installation therefor

Cold rolling installation, comprising means for allowing the product to run through a rolling plane, successively in at least two rolling stands operating in tandem, each stand comprising two housings between which at least four stacked rolls including two back-up rolls and two work rolls respectively, are slidably mounted, in a direction parallel to a roll load plane, and means for applying a rolling force between said rolls with adjustment of respective gaps, wherein at least one convertible stand is provided with at least two possible configurations, while maintaining, for both configurations, at least the same back-up rolls and the same means for applying the rolling force including respectively a four-high configuration fit for a first production range, with two work rolls and two back-up rolls and a six-high configuration fit for a second production range, with two work rolls, two intermediate rolls and the same back-up rolls and reversely, the work rolls and intermediate rolls being each rotatably mounted on two chocks, each provided with at least two back-up lugs for means for adjusting the conditions under which the rolling force is transmitted including means for bending the respective rolls, wherein on each side of the rolling plane, the roll bending means are the same in both of said at least two possible configurations and co-operate respectively with back-up lugs of the chocks of work rolls in the four-high configuration and back-up lugs of the chocks of intermediate rolls in the six-high configuration, respectively, and wherein said the back-up lugs of chocks or work rolls in the four-high configuration are offset with respect to roll axis, on the side opposite the rolling plane, and said back-up lugs of chocks of intermediate rolls in a six-high configuration are offset toward the rolling plane with respect to roll axis, so that said back-up lugs of work rolls and of intermediate rolls are arranged substantially at the same level and co-operate with the same bending means.