Study of clad layer thickness evolution during hot rolling of clad plate with composition S355+316L

The article is devoted to the study of the cladding layer thickness evolution during the hot rolling of a S355+316Lclad plate. In the production of clad rolled products, the main challenge is the significant non-uniform deformation of the dissimilar layers, leading to an uneven cladding layer thickness, which is regulated by standards. The aim of the work was a comprehensive study of the co-deformation of the layers to analyze the influence of the reduction strategy on the formation of the cladding layer geometry and based on this, to develop practical recommendations. To achieve this goal, an integrated approach was applied, which included determining the rheological properties of the studied steels over a wide range of temperatures and strain rates, as well as developing and subsequent verification of a three-dimensional mathematical model of the rolling process using the finite element method in the ANSYS software package. The model was validated against data from laboratory and industrial experiments, showing an error in predicting the final cladding layer thickness of no more than 7 %. Using the verified model, a numerical study of three different reduction strategies was conducted: a standard one, one with large reductions in the initial passes, and one with small reductions at the beginning of the process. The simulation results showed that the cladding layer thickness is significantly non-uniform along the length and width of the rolled sheet. The relative strain ratio varies from ⁓1.07 in the central part to 1.25–1.35 at the head and tail ends, leading to a difference in the cladding layer thickness of up to 24 %. It was found that the selected rolling strategies have an insignificant effect on the degree of this non-uniformity. The physical reason for the non-uniformity in the central part is the tensile stresses acting on the cladding layer from the base layer, while at the sheet ends the primary contribution comes from longitudinal metal flow and the “extrusion” effect. Based on the approximation of the shape of the thickenings, the amounts of crop required to meet standard requirements were calculated: ⁓365 mm from the head and tail ends and ⁓177 mm from each side edge of the sheet. The data obtained are of significant practical importance for optimizing the production processes of clad rolled products.