Шляхи зменшення різнотовщинності товстолистового прокату

Abstract

The purpose of the work is to develop scientific and technical proposals for reducing the longitudinal and transverse thickness variations of thick sheets when rolling on thick sheet mills. In recent years, there has been a constant increase in the cost of energy resources and increased competition between producers of rolled steel. Therefore, increasing the efficiency of the sheet rolling process by reducing the thickness variation and reducing the consumption coefficient is an urgent task. The Iron and Steel Institute of Z. I. Nekrasov National Academy of Sciences of Ukraine investigated the possibility of solving this problem in the conditions of one of the 3600 plate mills. Experimental and analytical studies of the formation of longitudinal and transverse thickness variations in thick sheets were carried out. The well-known fact has been confirmed that the main factor in the formation of longitudinal thickness variations is the fluctuation of the rolling force. Sheets produced on the 3600 mill have an average longitudinal thickness variation of 0.35-0.58 mm (the weighted average value for the entire assortment is 0.52 mm). The main factors influencing the transverse thickness variation are roll deflection, flattening of work rolls in contact with the strip, and roll wear. The average transverse thickness variation is 0.10-0.35 mm (the average for the assortment is 0.25 mm). The influence of the mass of the assembly batch of sheets on the wear of work rolls and, accordingly, the cross-sectional profile of the sheets was experimentally established. As a result of the research, three directions for solving the problem of reducing the variation in thickness of sheets were proposed: 1) regulating the allowance for the thickness of rolled products, taking into account actual data on the longitudinal variation in thickness of sheets by assortment groups; 2) implementation of an expert system for correcting the specified final thickness of sheets on the computer of the finishing stand regulator; 3) ensuring optimal values of convexity of the transverse profile of sheets. In order to reduce the convexity of the cross-section of the sheets, an experimental study was carried out on the use of convex work rolls in the finishing stand instead of rolls with a cylindrical profile. This ensured a decrease in the average convexity of the cross-sectional profile of the sheets from approximately the average initial level of 0.25 mm to the expected 0.15 mm and, accordingly, an increase in the yield of suitable by 0.3%, as well as a decrease in the waviness of the sheets. It is recommended to introduce convex work rolls into continuous operation in the finishing stand of thick-sheet condition 3600 (convexity of the upper roll is 0.15 mm, the lower one is 0.10 mm).