Development of Automatic Control System of Hot-Strip Mill Process Parameters

Abstract

It is observed that the contemporary trend of rolling development is widening of hot-strip mills assortment because of ultrathin hot-rolled strips production instead of cold-rolled ones. The advisability of the automatic control system of process parameters (such as tension, gauge, and roll speed) update is demonstrated on the examples of wide-strip mills 2000 and 2500 at Magnitogorsk Iron & Steel Works. Control algorithms for electric drives speed rates are examined, which provide proportional position control of finishing rolling speed under control and perturbation actions with corrective action transmission against rolling direction. Corrected digital algorithms of tension dynamic control enabling longitudinal grow-back decreasing due to accuracy increase of looper electric drive torque and loop size in interstand space computation are presented. The streamlined structure of automatic control system of strip gage (ACSG). The system realizes control method on base of indirect control with sensor values averaging over a specified period of time combined with direct control following exit gage signal and external correction providing perturbation actions compensation and draft redistribution in finishing trains. The developed system of automatic head end gage correction by moving rollers apart before strip enters mill with their subsequent return to specified position for main strip end rolling is demonstrated. The results of improved ACSG application investigations on operating rolling mill are presented. The method and the system of interactive tension and strip gage control are proved and examined whereby automatic correction of hydraulic roll screwdown position of the previous stand under perturbation and control actions caused by change of looper or roll screwdown of the next stand positions is implemented. The results of research and commercialization of the developed systems confirm technical-and-economic efficiency provided with reduction in input of materials, improvement in the quality of production and steadiness of the processing.