METHOD FOR CALCULATION THE MODES OF STRIPS COLD ROLLING ON MULTIPLE-STAND ROLLING MILL ENSURING COST REDUCTION OF SHEET ROLLING SHOP PRODUCTION. REPORT 2. AN EXAMPLE OF THE METHOD PRACTICAL USE ON FOUR-STAND ROLLING MILL 1400

Abstract

The second part of the paper describes the method practical use on four-stand rolling mill 1400. When rolling the chosen typical sizes, the task was to determine the specific rolling mode, which will ensure a minimum of the total specific energy consumption at the maximum rolling speed, maximum process stabilization (minimum breaks, idle times, etc.) and obtaining the specified quality of the rolled strips (no surface defects, meeting the thickness and flatness requirements). It was achieved by including the above requirements in the constraint system with respect to the determined rolling modes for the selected strip sizes. For example, ensuring a given (maximum) performance for a specific size and brand of a strip is equivalent to realizing a gi673 ven (increased) rolling speed in the absence of unscheduled downtime occurring in emergency situations (in particular, in strip breaks). The speed limit depends on the power of engines, which is included in the complex of structural and technological limitations. The obtained examples, given in the article, have shown that the use of the method leads to fulfillment of all the specified requirements, which, in turn, ensures a reduction in production cost and an increase in the mill’s productivity. The calculation of the cold rolling modes was reduced to selection and distribution of the crimping along the stands (passages – in the reversible mill) and to a choice of specific strip tension in the interstand spaces, on decoiler and coiler, and in setting the wedge of speeds in a particular system of constraints imposed on the input and output process variables as a function of the adopted optimality criterion. The task was solved using the conditional optimization method, through the specification of the optimization criterion. As such criterion, the total energy consumption of the rolling process was used, as requirements – technological and design constraints on the rolling parameters and conditions for strip stability to breaks and to formation of rolls surface defects (“brews”, “chippings”, etc.), as well as to strip breaks.