Modeling And Analysis Of Mechanical Parameters Of The Heavy Steel Plate Snake/gradient Temperature Rolling

The non-uniform deformation along the thickness direction is one of the main factors affecting the comprehensive properties of thick plate in rolling process.Increasing the total reduction rate can not meet the production demand due to the limitation of the opening of rolling mill and the maximum thickness of the slab.The thick plate with excellent mechanical properties in the center can not be obtained.Snake/gradient temperature rolling combines the advantages of snake rolling and gradient temperature rolling in improving deformation uniformity and shape,which provides a new idea for realizing uniform deformation of thick plate.The rolling force is the key process parameter to the guide equipment selection and actual production process.The establishment of rolling force model has very important research significance and industrial transformation value.Snake/gradient temperature rolling involves multi process,multi parameter and multi-objective cooperation,and the deformation zone is extremely complex.The existing mechanical parameters model can not be applied to snake/gradient temperature rolling.As a new rolling process,it is necessary to establish the prediction model of mechanical parameters because of the demand of rolling mill design and the setting of rolling process parameters.In this paper,the theoretical analysis,finite element simulation and experiments were used to study the temperature field,rolling deformation zone division and surface friction conditions of thick plate snake/gradient temperature rolling.The mechanical parameters model of the snake/gradient temperature rolling were established,and the effect of rolling parameters on rolling force and rolling torque was analyzed.The conclusions are as follows:(1)The temperature along thickness direction of rolled piece appears obvious delamination phenomenon after the ultra-fast cooling process before rolling.The rolled piece can be divided into top and bottom layers with obvious temperature drop and the central layer with basically constant temperature.The whole region can be divided into zone I,II,III and IV based on the position of neutral points and the roll offset.The whole rolling deformation zone was divided into 12 zones with different characteristics.The rolling deformation was divided into three different composition states based on the change of neutral points.And the friction equations of different composition states of deformation zone was established.(2)The deformation resistance of each layer was equivalent according to the delamination of longitudinal characteristics of the deformation region.The yield criterion was improved on the bases of uniform normal stress and non-uniform shear stress along vertical direction.The geometric relationship of the deformation region of snake/gradient temperature rolling with the same roll diameters and different roll diameters were analyzed.The analytical expressions of unit pressure for each deformation characteristic zone were established by the slab method.The integral constant of unit pressure was solved according to boundary conditions.And the position of neutral points were calculated by the principle of equal metal flow and the continuity of the unit pressure on the boundary.The analytical model of rolling force and torque for snake/gradient temperature rolling were established according to the composition of the deformation region.The error of the model computational results was small compared to the results of finite element simulation and experimental,which can be used to predict the rolling force and rolling torque of thick plate snake/gradient temperature rolling.(3)The snake/gradient temperature rolling with the same roll diameters and the different roll diameters was simulated by ANSYS LS-DYNA,respectively.And the curves of rolling force and torque were analyzed.The rolling force will decrease because the increase of roll speed ratio,roll diameter ratio and friction coefficient,and increases with the increase of roll offset,deformation resistance,rolling reduction and plate thickness.The magnitude and direction of rolling torque are related to the composition of deformation zone.