Automatic control of the sheet width on hot rolling mills.

Abstract

Controlling the sheet width using a computer on heavy plate mills (HPM) and roughing mill trains (RMT) of wide-strip hot rolling mills (WSHRM) must ensure the set width of the sheet (roll), rectangularity of the sheet (roll) in the plan characterized by the uniformity of the sheet width in the middle part along its length, as well as at the front and rear ends, and the minimal trimming of the front and rear defective ends of the sheet (so-called “tongues” and "swallowtail"). Forming the desired sheet width is carried out either in jointly working vertical and horizontal mills in a reversible mode or in a continuous non-reversible group of mills (vertically-paired – horizontal). With the leading participation of the authors, there were carried out the development of the automated process control system (APCS) and studies aimed at regulating the width in the RMT of mill 560. Mathematical models describing natural and additional expansion and the requirements for their accuracy are presented in famous scientific works. To assess the accuracy of the characteristics, experimental studies were conducted on a laboratory mill. The rolling conditions in the RMT of mill 560 were simulated during the research. The analysis of experimental data and data obtained through the calculation using various formulas provided in literary sources showed that all known models do not meet the accuracy requirements set by the APCS for the RMT of mill 560. Therefore, new mathematical models of expansion were developed. The paper presents the mathematical models for changing the width in the middle part along the length of the roll and the models for changing the width at the “head” and “tail” of the roll. A method for determining a roll gap is described, which implements the law of change of the gap of vertical rolls that eliminates deviations in the width of the roll from the initial (before rolling) value. The testing of the developed mathematical models under the conditions of the technological process in the RMT of mill 560 showed their ability to solve the problem of controlling the sheet width in real time.