Research On Strip Profile And Flatness Control Of Nuclear Power Zirconium Alloy Of Multi-schedule And Multi-pass In Hot Rolling

China has great development of nuclear power in recent years,since the completion of Qinshan Nuclear Power Station,Guangdong Daya Bay Nuclear Power Station,Ling ’ao Nuclear Power Station and Tianwan Nuclear Power Station.At present,China has more than 49 nuclear power stations in operation,which makes China’s independent and controllable demand for high-quality nuclear power zirconium materials increasingly.As one of the most difficult and influential research frontiers in the field of international rolling,the profile and flatness control has made remarkable progress and rich achievements in the theory and practice for steel,aluminum alloy and other metal strip rolling in recent years.Zircaloy is widely used in the field of nuclear power,and is a sensitive strategic material in the world.The key technology of Zircaloy strip preparation has been blocked,and there are few reports about Zircaloy strip rolling process and the profile and flatness control.The profile and flatness control is an important quality index of nuclear Zircaloy strip rolling.Multi-pass hot rolling is one of the important processes and key links in the manufacture of nuclear Zircaloy strip.This paper takes a key industrial hot rolling production line with the largest output of Zircaloy strip for nuclear in China as the research object.According to the characteristics of multipass rolling of Zircaloy strip for nuclear,aiming at how to rolling out high quality Zircaloy strip stably problem,we combined literature research,experimental research,theoretical analysis,finite element simulation and industrial test verification and application to research on profile and flatness control of multi-pass hot rolling of nuclear Zircaloy strip.The specific research contents and main achievements are as follows:(1)According to the characteristics of multi-schedule and multi-pass production of Zircaloy strip,the temperature prediction,rolling force calculation and were studied.A constitutive relationship of zirconium alloy based on IPSOSVR algorithm is proposed,which provides a basis for establishing a high-precision finite element model of hot rolled zirconium alloy strips.Under the constraints of three hot rolling schedules,more than 20 passes,single stand and other conditions,the rolling force is the key factor to meet the rolling mill capacity to achieve stable rolling of Zircaloy strips.Firstly,the temperature model of Zircaloy strip under hot rolling process is established.And the temperature correction value is obtained by calculating the temperature rise and temperature drop of each rolling process and each pass.Secondly,the deformation resistance and temperature model of Zircaloy are predicted by the high temperature stress and strain,and the external contact friction stress function regressed by the process parameters of hot rolling process.Based on the particle swarm optimization algorithm,the hot rolling force prediction model of Zircaloy is established.(2)Combined with the characteristics of mill,the finite element model was established to analyze the strip profile and faltness control performance change rule of Zircaloy under different rolling schedule,and to eliminate residual stress under the capacity of exiting mill,the temperature control tempering process be added between the second rolling process and the third rolling process in the original process system.By analyzing the factors such as bending force,width and number of passes on the strip profile and faltness of Zircaloy,the problem that the original deformation rolling schedule produces wave shape on the third rolling process of Zircaloy strip is clarified.Combined with the influence of temperature,the set value of process parameters for adjusting the profile and faltness of Zircaloy strip and affecting the temperature change of hot rolling process is given,which provides a basis for improving the strip profile and faltness control ability of Zircaloy strip.(3)To realize the stable rolling of Zircaloy strip with narrow thermoplastic range,temperature change and mechanical deformation,the initial temperature of hot rolled Zircaloy strip was determined for the first time based on the constraints of rolling mill capacity,total reduction rate of rolling range and pass reduction rate.The total reduction rate of each rolling range was redistributed,the pass reduction was changed,and the hot rolling deformation system of Zircaloy strip with good profile and faltness was proposed.We design the varing contact backup roll(VCR),and we established the bending force model based on VCR backup roll.Industry application shown that the hot rolling deformation schedule of Zircaloys with the goal of good strip profile and faltness and temperature distribution can improve the strip profile and faltness quality.