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The grains in the center of the heavy steel plate can be refined by the snake/gradient temperature rolling, and the deformation penetration, the microstructure, and the properties of the steel plate will be improved. The existing rolling mechanical models are not suitable for the snake/gradient temperature rolling, so it is necessary to establish the mechanical parameters model of the snake/gradient temperature rolling to instruct production. The yield criterion of rolled material was modified based on the idea of equivalent flow stress. The element stress analyses were carried out based on the uniform normal stress and nonuniform shear stress in the vertical sides of each slab. Then the equilibrium equation of the unit pressure based on the slab method was established on this basis. The deformation region was divided into three layers (the top layer, the bottom layer, and the central layer) and maximum four zones (back slip zone, front slip zone, cross shear zone, and reverse deflection zone) according to the temperature distribution and position of the neutral point, and then the 12 zones were formed during the snake/gradient temperature rolling. The boundary conditions of the existence of the back slip zone, the front slip zone, and the cross shear zone were established according to the relationship between the threading angle and the neutral angle. The accurate mechanical parameters model of the rolling force and rolling torque of the snake/gradient temperature rolling with the same roll diameters was set up on this basis. The ANSYS software has been used in the rolling process simulation by many scholars, and the calculating precision has been verified. So the rolling processes were simulated by the ANSYS software to validate the model precision. The results show that the maximum relative deviation of the rolling force analytic model is less than 7% compared with the numerical method, and the maximum relative deviation of the rolling torque analytic model is less than 11% compared with the measured results. The mechanical parameters model can accurately predict the rolling force and rolling torque during the snake/gradient temperature rolling with the same roll diameters, so as to provide a theoretical basis for the design of rolling mill and the setup of the process parameters.

The strain after rolling plays an important role in the prediction of the microstructure and properties and plate deformation permeability. So it is necessary to establish a more accurate theoretical strain model for the rolling process. This paper studies the modeling method of the equivalent strain based on the upper bound principle and stream function method. The rolling deformation region is divided into three zones (inlet rigid zone, plastic zone, and outlet rigid zone) according to the kinematics. The boundary conditions of adjacent deformation zones are modified according to the characteristics of each deformation zone. A near-real kinematics admissible velocity field is established by the stream function method on this basis. The geometric boundary conditions of the deformation region are obtained. The deformation power, friction power and velocity discontinuous power are calculated according to the redefined geometric boundary conditions. On this basis, the generalized shear strain rate intensity is calculated according to the minimum energy principle. Finally, the equivalent strain model after rolling is obtained by integrating the generalized shear strain rate in time. The plate rolling experiments of AA1060 and the numerical simulations are carried out with different rolling reductions to verify the analytic model precision of the equivalent strain. The results show that the minimum and maximum relative equivalent strain deviation between the analytic model and the experiment is 0.52% and 9.96%, respectively. The numerical calculation and experimental results show that the model can accurately calculate the strain along the plate thickness. This model can provide an important reference for the rolling process setup and the microstructure and properties prediction.

The corrosion and discharge behaviors of AZ91 magnesium alloy after hot rolling with different deformations (0%, 20%, 30%, and 40%) are systematically studied in this article. The results indicate that AZ91 without rolling deformation (0% rolling deformation) possesses the most outstanding corrosion resistance; at high current densities (40, 50 mA cm−2), the discharge activity of AZ91 after hot rolling with 20% deformation is optimal, while 0% rolling deformation shows the most excellent discharge activity at low current densities (5, 10 mA cm−2). Combined with the observation results of microstructure, it demonstrates that the corrosion resistance and discharge activity of AZ91 are closely related to the fragmentation of the second phase, the distribution of the second phase at the grain boundary, and the increase of the grain boundary after hot rolling.