Modeling Analysis And Research On Plate Curvature Of The Heavy Plate Snake Rolling

Heavy plate with high performance is widely used in construction engineering,ships,offshore platforms,pressure vessels and other major high-end technical equipment fields,and it is a very important structural material.However,the micro-structure and property in the center of the heavy plate is not well because of the little deformation in the central region.Confine to the mill opening degree and mill stiffness and the total thickness of the casting slab,it is difficult to satisfy the total rolling reduction requirement.Then the insufficient deformation in the central region problem appeared due to the little total rolling ratio.This problem has become the key technical bottleneck to improve the quality of the heavy plates.The snake rolling is beneficial to improve the heavy steel plate central deformation,and keeps the plate shape well at the same time.Then,the established model was not suitable to calculate the plate curvature for the snake rolling because of the obvious difference of the characteristic of the deformation region.On the other hand,the composition of the deformation region may be different due to the different neutral point position during the snake rolling.In fact,the deformation region was divided into four different zones at most which was depended on the positions of the two neutral points,and this number could be dropped to three or two in some other conditions.But the existing studies on the plate curvature modeling of the snake rolling didn’t consider the composition of the deformation region which would result in a great error.Therefore,the in-depth research is required to conduct a comprehensive evaluation of the snake rolling and predict the plate curvature accurately.The main conclusion of the dissertation are as follows:(1)The snake rolling can be divided into the same diameter and different diameter methods.Although the two methods can achieve snake rolling,they have different effects on the position of the neutral points due to different realization ideas,so the composition of the deformation region is different,and the plate curvature models of the two are also different.The two types of snake rolling deformation region can be divided into to four different areas: back slip zone(zone Ⅰ),cross shear zone(zone Ⅱ),front slip zone(zone Ⅲ)and reverse deflection zone(zone Ⅳ).However,the four zones may not exist at the same time due to the location of neutral points.According to the position of the neutral points,there are three situations: Ⅰ,Ⅱ,Ⅲ,Ⅳ;I,Ⅱ,Ⅳ;Ⅱ,Ⅳ.(2)The paper establishes the theoretical calculation model for the plate curvature of the snake rolling with the same and different diameter based on the slab method.The deformation region with different composition cases were analyzed,and the models of the specific pressure and the accumulated shear strain deviation between the upper and lower parts of the plate with every case were established.The plate curvature caused by shear strain was calculated on this basis,and the plate curvature caused by the axial strain was also calculated according to the flow criterion.The homogeneity coefficient E was introduced during the plate curvature modeling process to make the model more accurate.Then the total plate curvature model was established in the end.(3)The finite element simulation of the same and different diameter snake rolling was carried out,and the results were compared with the results of the established theoretical calculation model.In addition,experiments were carried out.The results show that the error of the theoretical model can be controlled within 12% compared with the simulation results,and the error of the theoretical model can be controlled within 11% compared with the experimental results,which verifies the accuracy of the model.(4)The influence of different process parameters(roll offset,roll speed ratio,roll radius ratio,rolling reduction and so on)on the plate curvature of the snake rolling is obtained according to the calculation results of the theoretical model.The theoretical model can accurately predict the plate curvature.The research about the plate curvature modeling will provide important references for the heavy plate snake rolling production.