PR-317-025 - 2002 Mechanical Working Steel Processing Proceedings

Three-Dimensional Simulation of Snake Motion In A Tandem Cold Mill

H. Matsumoto and A. Ishii

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Snake motion is a long persisting problem inherent in flat rolling. It is a walk or deviation of the stripbeing rolled from the mill center, and is caused by any asymmetry in rolling conditions in the right/left orwidth direction, including the asymmetrical distributions of the roll gap, the geometry and material of theentry strip, the strip temperature, the friction coefficient, or anything else. Since snake motion sometimesappears in a zigzag form as the evidence of the operator's desperate reaction, let it be referred to by thisnaming. It results in various asymmetries in the geometry of products, such as asymmetrical thicknessdistribution, camber or bend in the right/left direction, asymmetrical buckling, etc., thus lowering theproduct yield. To the worse thing, it often causes an accident called squeeze, that is, the strip walks to outside the roll barrel. This is known as so-called tail crash in hot strip rolling and strip breakage in cold rolling. To avoid these accidents, we have to restrict the rolling conditions, such as the minimum gauge of the product rolled, the strip tension, the maximum reduction in thickness, the rolling speed, etc., within some compromised range from the viewpoint of the other requirements.

Keywords: strip rolling, cold rolling, tandem rolling, dynamic simulation, pseudo-3-dimensional theory,generalized 2-dimensional theory, asymmetrical deformation, snake motion