Microstructure Simulation For Heavy Backup Roll

Large forging was widely used in equipment manufacturing as based pieces and key-module. The production of large forging is an important constituent of heavy machinery manufacturing, the level of its production varieties, weight level, quantity and production equipment, etc. is an important marking of the country's economic strength and industrial development level. The application field of large forging requires that forgings have better immanent quality and performance in complex conditions. Therefore the production and research of large forging will tend to scientific and modernized direction.Finite element numerical simulation technology is used not only for forecasting and controling the internal mechanics performance in the forming process of the forging, but also for studying on the forging internal microstructure in the deformation process. Through forecasting the microstructure evolution of forging process, we can take control of the productive process conditions and the thermodynamics forming process parameters of material, to realize the control of microstructure evolution in forming process and eventually get ideal forging organization with good mechanical properties. The application of the numerical simulation technology in forging fields greatly reduces the production cost and realizes the transformations of traditional qualitative forging forming to quantitative research and experience design to scientific.First, the relation between stress and strain during the hot compressive deformation process of backup roll material 45Cr4NiMoV steel is studied through the Gleeble-1500D thermal compressive deformation process, and the stress-strain curve model of material is built by the experimental results; The relationships of the peak stress with strain rate and temperature are analyzed during hot compressive deformation process, the results indicate that the peak stress is decreased with the rise of deformation temperature, and increased with the rise of strain rate at the same temperature is obtained, the change rule has closely relation with the microstructure evolution during heat deformation of the material; And according to the change of peak strain value at different temperature and different strain rates during the hot compression process, material's critical strain model is identified.Backup roll upsetting and stretching process are simulated in Deform-3D finite element analysis software based on the material's model obtained by the physics experiment, and the forging surface temperature distribution, heart equivalent stress and equivalent strain state are analsyzed under different anvil wides. And a more reasonable backup roll process scheme is determined.Two-dimensional cellular automata dynamic recrystallization model is established with the hot compress test data and material critical strain model of the backup roll material; Then the dynamic recrystallization during the upsetting and stretching deformation process of backup roll is simulated through the microstructure module in the Deform-3D, and the relationships between the factors such as temperature, strain, dislocation density and the dynamic recrystallization are summarized: the dislocation density is increased with the strain increasing, which will provide power for the formation of dynamic recrystallization new nuclei; Part of dislocation is released with the nucleation process; Meanwhile,new nuclei grow up rapidly under the function of high temperature and the asymmetrical distribution of the dislocation energy. These process proceed in the whole upsetting and stretching deformation.Therefore, if the forgings cast organization is completely changed and obtaining homogeneous ideal grain are expected, enough forging ratio in upsetting and stretching process and enough strain in the heart of forgings which is aimed to completely forge the heart are necessary.The simulation analysis on the upsetting and stretching process of 45Cr4NiMoV backup roll and the dynamic recrystallization through the deformation predicted results are accordance with the theories, and these results could provide basis parameters to the heavy backup roll process.