Theoretical and experimental study on the producible rolling thickness in ultra-thin strip rolling

The cold rolling process of a thin strip is difficult to continue when the strip has been thinned to a certain thickness. A limit thickness, which is referred to as the limiting producible rolling thickness below which plastic deformation does not occur, exists even if the rolling force and the number of rolling passes are increased. The Stone formula is the most common approach for predicting this limit, but its results are inaccurate in experiments or in ultra-thin strip-rolling production. In this study, the variation laws of the contact profile and rolling pressure of ultra-thin strips with different thickness specifications at different reductions were obtained by finite element simulations, indicating that the Stone minimum thickness can be regarded as the critical thickness that exists when a neutral zone is present under a minimal reduction. A theoretical calculation model of producible rolling thickness for an ultra-thin strip based on Fleck theory was established and verified by experiments. When this model is used, the single-pass reduction can be obtained in accordance with the given unit width rolling force, the technical parameters of the rolling mill, the yield strength of the material, and the initial thickness of the strip. The formula for the conditional limiting producible thickness considering the restriction of rolling force was corrected. The relationship between single-pass reduction and the ratio of the initial thickness of the strip to the theoretical limiting producible thickness under the condition of the maximum allowable rolling force of the rolling mill was discussed. This study provides theoretical guidance for practical production by defining the product specification ranges and rolling regulations for existing rolling mills and determining the roller diameters and force and energy parameters for the design of rolling mills.