Analysis of force fluctuation in order to determine structural defects in hot strip rolling mills

Abstract

Structural defects of the mill have considerable effect on the product quality in conventional strip rolling. Since the working rolls are in direct contact with the product, geometrical deviation of them is the most effective parameter on the product quality. In this paper a dynamic model for evaluating mill response to different major structural defects for hot strip rolling is presented for the first time. The model has two main sub-models; the stand elastic model and the strip rolling plastic model. Roll surface flattening and the material hardening due to strain and strain rate are the main sources of the nonlinearities in the mill and the rolling process sub-models respectively. In the presented procedure, in each step, both the models were linearized around the steady state working point and the stiffness matrix was updated in each step. The SIMULINK tool of the MATLAB software was employed to simulate the interactions of the sub-models. The model is able to undertake seven stands in a tandem four-high mill simultaneously Defects such as ovality and eccentricity of work roll and backup roll have been modeled and the simulation results are in very good agreement with data gathered from an industrial mill data logger.

Keywords

• Hot strip rolling, forced vibration, structural defect

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