Research On The Numerical Simulation Of C-Mn Steel Visco-plastic Rolling In High Temperature

The thick steel plates are being widely used in the people’s livelihood and equipment manufacturing.Many weakness however occurred in the traditional hot rolling,such as high energy consumption and low production efficiency.Especially,it was hard to acquire enough core deformation of continuous casting slab,and it could not fully improve the defects such as core loose and shrinkage.This paper proposed a new rolling technique that directly set large reduction rolling mill at the end of the continuous casting machine.The continuous casting slab deformed at the complete austenite region whose temperature was near the melting point.The steel had a strong deformation capability then,and the new process could also save energy and improve core quality of cast slab.This paper combined research results of rheology of C-Mn experimental steel with finite element method,and compared the relevant parameters of the new process with the first pass of the old one.The main research results were as follows:(1)In the lab,the compression test whose deformation temperature range were 1200-1400 ℃ and strain rate range were 0.1-1 Os-1 was completed,using the MMS200 testing machine.The stress-strain curve was got through the test,and this set up a foundation for the further study of the mechanical models and the optimum region for hot processing.(2)Based on the stress-strain curve,the function expression of peak stress and peak strain was established,and the value of deformation activation energy was 332.376kJ·mol-1.The high temperature viscoplastic constitutive models were established from the points of view of characterization and dynamic recovery-dynamic recrystallization theory.Through error analysis,the theoretical model could not only have higher prediction accuracy,but also could reflect the nature of dynamic recovery and dynamic recrystallization in thermal deformation.(3)Power dissipation efficiency maps and instability criteria maps were drawn,and the process window of experimental steel was determined.Under the high reduction and high temperature deformation conditions,a higher deformation temperature and strain rate of less than 0.2s-1 should be chosen,so it could ensure the full dynamic recrystallization process and avoid the deformation instability zone.Thus the layout of the direct connection of continuous casting and large rolling mill was proven,that was beneficial to control the deformation producing in the reasonable process interval.(4)By comparing the simulation results of two kinds of processes,the work piece of the high reduction and high temperature technique had a higher average temperature,so it was easily deformed,and had lower rolling force.Meanwhile,at the rolling deformation zone of the high reduction and high temperature process,a bigger core and surface temperature difference was formed,which promoted the core of work piece producing greater deformation,so it was conducive to the improvement of product quality.The characteristic of "low energy consumption and high quality" was reflected in the high reduction and high temperature process,and it solved the problem of traditional technique,which made it hard to acquire enough core deformation of continuous casting slab.(5)Combined with the new technique calculation results,strip edge crack and roller heating were analyzed.Compared the evolution of the crack in the corner during the alternating rolling process of vertical-flat and flat-vertical,a conclusion could be drawn reveling how alternating rolling process of vertical-flat could promote the corner crack healing in the high reduction and high temperature rolling process.