| With the development of science and technology, the industry and the various of departments'quality requirements for strip steel are becoming more and more strict, particularly for the hot-rolled material prepared for cold-rolled. It's strict for the shape of strip, as well as the crown and the cross-sectional shape. If the strip's cross-section shape is not good, then it will cause many defects, such as large crown and local defect, which will affect the quality of products and its working life seriously. It's required to obey the principle that keeping crown as a fixed variable to maintain a good shape. Some research has been done, which is combined with practical productivity of a hot rolling mill, the study includes: the influencing factors to crown; the influence on roll wears out, roll temperature and roll deflection change which are caused by the working rolls shift. In this paper, author has analyzed that a series of factors influence on crown to a certain extent, with the help of Minitab software, and mainly conclusions are as follows;(1) The load of F3,F6 decrease ,the load of F2,F4,F5 increase, the bending force increases, the size of roll shape decreases, the edge drop decreases and the absolute value of wedge decreases, which all lead the crown decreases. The roll thermal crown will be basically formed in about 30mins. If the roll is uneven wearing and rolling schedule is unreasonable, the result of crown will be affected directly. Roll diameter to the impact on the crown is not obvious. Crown will be changed with the amount of working roll shift and the life cycle of working roll.(2) Working roll shift makes roll's absolute wear decrease and relative wear wider, which means homogenizing wear; the roll temperature decreases 3~5℃, and gradually homogeneous decreasing and distributing along the barrel. These two points can provide a stable, good working roll shape, then the cross-section shape of strip is good; the position of maximum deflection is opposite with shifting direction. When the shift value is 60~100mm, the deflection of roll will increases with the increasing of the shift value. When the shift value is out of the range, then the change will be opposed.(3) By studying the One-way analysis of variance of Q235B, all the p-value that affect crown, including thickness, temperature, rolling force, roll bending force and roll shifting, is less than 0.05.It indicates that they all have a great effect on crown. By the regression analysis with the same factor of SPHC, it can be known that the thickness of the plate has greater influence to crown than width, the FT0 has greater influence to crown than FDT and RT2, F1~F4 rolling force on the plate crown has greater influence than the F5 and F6;The bending force and roll shifting of F6 have greater influence to crown than the other mill, and draw the corresponding regression equation. It's also informed by studying the regression analysis with heterogeneous factors: the rolling force has greater influence to crown more than the temperature and bending force, bending force has greater influence to crown more than the temperature and roll shifting. |
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