WANG Dong-cheng
钢铁研究学报(英文版)
The shortcomings of an exit stress variation formula which has been well accepted are analyzed; it is found that the exit stress variation formula violates the premise of the law of volume constancy. The shortcomings of an entry stress variation formula are analyzed too, and the basic assumption of the formula is uniform exit velocity. However, for a rigid-plastic material uniform exit velocity implies that the lateral distribution of elongation is uniform, so the exit stress must be uniform and any type of flatness defect is impossible, which is contrary to the practice. In fact, entry and exit velocity variation influence entry and exit stress variation, and entry and exit stress variation influence entry and exit velocity variation too, so a precise explicit stress variation formula cannot be got easily. Considering the relationship between stress variation and velocity variation, an iteration method is presented to calculate entry and exit stress variation of cold rolling strip. To avoid divergent phenomenon of the iteration course, a relaxation factor method is adopted. The calculation results are compared with the entry and exit stress variation formula commonly used by many researchers. The difference is remarkable, while the result calculated agree more well with measured result if the exit elastic recovery zone is considered. Specially, the incoming flatness′ propagate efficiency calculated gives a more realistic result.
关键词:
cold rolling
,
stress variation
,
velocity variation
,
iteration method
,
relaxation factor method
ZHANG Yun
,
YANG Quan
,
WANG Xiao-chen
钢铁研究学报(英文版)
It is a complicated problem for cold-rolled strip to improve asymmetric strip shape in strip production. A roll system and strip coupled model of six-high cold rolling mill was established with finite element method to estimate the effect of intermediate roll shifting, tilting, symmetric and asymmetric bending technologies on strip profile. To reduce asymmetric defects of strip shape as much as possible, some control strategies were proposed, including tilting and asymmetric bending of intermediate roll and work roll. The combinations of these three control strategies can effectively eliminate asymmetric strip shape defects. Finally, the closed-loop control model of asymmetric flatness at the last stand was given, and the flatness control system with the function of asymmetric strip shape control was also designed for cold tandem mill.
关键词:
cold rolling
,
monitoring characteristics
,
asymmetric strip shape
,
control strategy
