Research On Mechanical Parameters And Deformation Permeability Of Heavy Steel Plate Snake Rolling

The heavy steel plate with fine performance has been widely used in the field of major high-end technical equipment such as military equipment,warship,nuclear power,offshore platform,pressure vessel,heavy machinery and so on,which is very important structural materials.Heavy steel plates have low mechanical properties of the inner region due to insufficient deformation of the inner region,especially impact properties.In order to improve the mechanical properties of the inner region,the method of increasing the total rolling reduction ratio is generally used to achieve uniform deformation.However,limited by the production capacity of the cast ingot and the opening degree of the mill,the total compression ratio is generally difficult to meet the requirement.In this study,a heavy steel plate snake rolling process is taken as the research object.To improve the deformation uniformity of the heavy steel plate and the performance of the inner region structure,the theoretical analysis and numerical calculation methods are used to study the snake rolling mechanical parameters and the influence mechanism of thickness direction deformation permeability in the heavy steel plate.The main achievements of the dissertation are as follows:?1?Through the rolling principle and the geometrical relationship of the snake rolling deformation zone,the calculation model for the rolling reduction,threading angle and neutral angle of the top and bottom work rolls of the snake rolling were established.The mechanical analysis of snake rolling rolled biting into the roll gap is carried out by statics theory.It is deduced that the natural biting condition of snake rolling is that when the friction anglebis not less than the average value of the top work roll threading anglea₁ and the bottom work roll threading anglea₂,it can bite naturally.Compared with the Symmetrical rolling,the results show that the snake rolling process does not have a significant effect on biting conditions.?2?The finite element software ANSYS/LS-DYNA was used to numerically simulate the snake rolling process of heavy steel plates.The influence of different rolling methods and rolling process parameters on the thickness direction deformation permeability of heavy steel plate is discussed.The results show that the shear stress produced by snake rolling in the deformation zone contributes to deformation penetration into the inner region of the steel plate.And the effective strain in the inner region of the steel plate increases with the increase in the speed ratio.Increasing the rolling reduction amount can significantly increase the effective strain of the inner region of the steel plate,and also improve the uneven deformation in the thickness direction of the steel plate.Under the same reduction rate,the thicker the steel plate is,the worse the microstructure properties of the inner region are,and the more uneven the deformation of the steel plate thickness direction is.The influence of friction coefficient on the deformation is mainly concentrated on the surface of steel plate,which has little influence on the deformation of steel plate inner region.The effect of roll offset and rolling speed on the equivalent strain in the thickness direction of steel plate is very small.?3?Based on the slab method,the mechanical calculation model of the snake rolling with the same diameter/the different angular velocity and the same angular velocity/different diameters was established.The rolling deformation region will be divided into back slip zone,front slip zone,cross shear zone and reverse deflection zone according to the direction of the friction during the snake rolling process.The four zones may not be existing at the same time.The boundary conditions of existence of the back slip zone,front slip zone and cross shear zone were established according to the relationship between threading angle and neutral angle.The accurate calculating models of the rolling force and rolling torque were setup according to the composition of the rolling deformation zone and the boundary condition.The analytic method calculation results are basically consistent with the numerical simulation results.The mechanical parameters model has a certain degree of calculation accuracy.