Study on the broken edge wave problem of cold rolled thin and narrow gauge low carbon steel strip
With the enrichment of cold rolling products and specifications,the shape control ability of cold rolling mill is facing great pressure and challenge.Aiming at the problem of broken edge wave of thin and narrow gauge low carbon steel strip,which is difficult to solve in the industry,experimental and simulation studies were conducted on the strip shape of a 1 970 mm tandem cold rolling mill.The results indicate that the broken edge wave is generated in the upstream stands,gradually digested in the downstream stands,and ultimately inherited to the outlet.The reason for the generation of broken edge wave:on the one hand,in the process of hot finishing rolling of low carbon steel,the edge temperature drops too fast,resulting in coarse grains at the edge,which makes the edge hardness about 15HRB lower than that in the middle On the other hand,the ability of wide rolling mill to control roll gap crown is limited in the narrow strip rolling process,and the difference of roll elastic flattening degree at the edge and middle of the strip,both are the causes of the problems.Then,a series of measures to improve the broken edge wave are put forward,including desig-ning the work roll contour with taper at the edge and VCL backup roll contour to reduce the extension of strip in the edge area,reducing the rolling force of five stands mills to improve its ability to digest broken edge wave,trimming at the inlet of acid rolling or adjusting the hot rolling process to improve the uniformity of microstructure uniformity.The experimental results indicate that the superimposed use of edge heating has a significant improvement effect,and the shape IU value is reduced by 43％.After the application of optimization meas-ures,the occurrence rate of strip shape with thickness smaller than 0.8 mm and width smaller than 1 250 mm is reduced from 40％to 0.5％,and the control level of strip shape is about 1 IU.
cold rolled thin gauge and narrow stripbroken edge wavemicrostructure uniformityroll gap crownroll contouredge heating
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