Quad Engineering developed software to simulate the formation of ridge buckles in cold rolling. Through the simulation, it is found that the ridge buckles can be reduced through use of upstream mill stands with higher local rigidity and/or downstream mill stands with lower local rigidity. The "local rigidity" of a mill stand is a new term introduced here, which denotes the capability of a mill stand to resist local work roll flattening. Further analysis shows that this finding is applicable to all shape defects in general, and the shape defects have self-cure capability, which is sensitive to local rigidities of the mill stands. The shape defects' "self-cure capability" is another new term introduced here, which denotes that the capability of the strain energy in latent shape defects tends to release itself in the subsequent rolling passes. The shape defects' self-cure capability and its sensitivity to local rigidity are particularly useful in reducing ridge buckles. Based on these findings, several new methods to reduce ridge buckles are proposed, such as using the first stand of significantly higher local rigidity, using the last stand of significantly lower local rigidity, and using an additional stand of very high local rigidity upstream of a cold mill. The effectiveness of the proposed methods is compared through simulation. Use of a skinpass mill with very high local rigidity for flattening the ridges before cold rolling is the most effective of the proposed methods. Since the local rigidity of existing skinpass mills is similar to those of typical cold mills, they are not suitable for this application. To fulfill this new application, a new ridge-flattening skinpass mill is developed.
展开▼
