Thermo-mechanical Coupling Deformation Analysis Of Slab Continuous Casting Process

Slab continuous casting technology,as one of the main technologies introduced into China’s iron and steel industry,has played a very important role in the development of China’s iron and steel industry.In the process of slab continuous casting,after the initial shell is formed by oscillating mold,the slab is pulled into straight-bending section by the straightening roller under the at the secondary cooling.The shell grows and thickens and the billet completely solidification in the subtended arc section,straightening section and horizontal section.The slab is also straightened during the pulling process.Finally,the billet is cut for finished products.In the running process,the continuous caster is subjected to own gravity,roller pressure,pull force,pull resistance force,contact force and thermal loads.The thermal loads are generated by heat conduction,heat radiation and convection heat transfer with surrounding steam.Therefore,the continuous caster deforms easily,resulting in the excessive changes of subtended arc accuracy and roller gap.These excessive changes will cause shell bulge deformation,billet fracture damage,center segregation in billet,bleed-out in billet and other malignant accidents.In this paper,a complete three-dimensional structural model and a three-dimensional thermal-mechanical coupling finite element model of the overflow line equipment(so called streamline equipment)are established for the No.4 Continuous caster of the second steelmaking in a steel plant.The calculation method of roller gap and roller rotation is put forward.The overall deformation of the caster under mechanical load and thermo-mechanical coupling loading were calculated by using the finite element model.The deviations of the subtended arc precision,roller gap,roller bending,roller rotation and axial movement of roller were solved.The deformation mechanism that influences the subtended arc accuracy and roller gap was analyzed.The mechanical stresses and thermal-mechanical stresses of the main cater equipment were calculated by the finite element model.The results show that the maximum deviation of the subtended arc accuracy is 18 mm and the maximum roller gap reaches 11.4 mm under thermal-mechanical loads.They are the six times and fourteen times of those under mechanical load,e of the caster under thermalmechanical coupling,which is 6 times of that under mechanical loads,respectively.In addition,the relative rotation between the upper and rollers and the axial movement of roller under thermal-mechanical loads are three times and five times of those under mechanical loads.It indicates that the thermal loads are the main loads that cause the deviation of subtended arc accuracy and roller gap.To prevent the excessive deviation of subtended arc accuracy and roller gap,the dynamic soft reduction technology was applied to control the subtended arc precision and roller gap.The drawdown curve was obtained,which can provides a theoretical basis for the control of the drawdown in the actual production process.Through the deformation analyses of continuous caster under mechanical loads and thermal-mechanical loads,the deformation mechanism that affects the subtended arc accuracy and roller gap was investigated.It shows that the deformations of banana-seat and straighteningseat are the main influence factors for subtended arc accuracy,and the deformations of bananaset,straightening-set,tension leveler and roller are the main influence factors for roller gap.Therefore,strengthening the thermal stiffness of banana-seat and tension leveler is the key to avoid the excessive deviation of subtended arc accuracy and roller gap and to ensure slab quality.