Basic Theoretical And Experimental Research On The Roll Profile Electromagnetic Control Thecnology Of Strip Mill

Cold rolled strip is an important part of strip products.At this stage,China has many rolling equipment for producing cold-rolled strip,and the production capacity is sufficient to support the market demand.However,there are problems of surplus low-end products and insufficient high-end products in actual production.Therefore this advanced technology is explored and applied on the conventional rolling machine and rolling production line to improve the quality and potential additional value of strip products,which is an effective method to facilitate industry restructuring and upgra ding.Flatness is the core indicator of cold-rolled strip products quality.The problem of low-order strip shape can be controlled quickly and effectively by the existing flatness control technology,but the problem of high-order strip shape cannot be controlled quickly and effectively,and it is urgent to develop a new flatness control technology to improve the ability of high-order strip shape.Roll profile electromagnetic control technology(RPECT)is a new flatness control technology.Based on induction heating technology and using the thermally driven and internal constraint mechanism of an electromagnetic stick,the technology cleverly converts the energy of induction heating into a thermal-mechanical hybrid power source,which greatly enhances the response rate of the roll crown,and can achieves micro-scale flexible roll profile control.This technology has a very broad application prospects,but related research is still in the blank.Therefore,this paper will carry out research around RPECT of strip mill,and provide theoretical basis for its industrial application.Firstly,based on the principle that the radius variation of roll surface can be converted into circumferential strain,a new method is proposed to achieve multi-point and real-time measurement of the electromagnetic control roll profile in non-rotating state.Combining this technology with RPECT,a single electromagnetic stick ?270mm×300mm roll profile electromagnetic control experimental platform(RPECEP)is independently designed and built.Based on the RPECEP,the feasibility of roll profile measurement technology and RPECT are confirmed by experiments.Meanwhile,based on t he mathematical model of electromagnetic field,temperature field and stress field,an electromagnetic-thermal-mechanical coupled axisymmetric model of electromagnetic control roll is established by commercial finite element software,and the calculation accuracy of the model is verified by experiments.This provided an effective simulation model for researching the RPECT.Secondly,the effects of different process parameters on the roll crown,the growth rate of roll crown and the roll profile curves are analyzed,and combined with industrial application conditions,the reasonable process parameters of the RPECEP are determined.The bulging principle of RPECT is discussed,and optimal time period for the roll profile control are determined.The strategy of maintaining the roll crown and the roll profile curves stability after bulging is analyzed,and the roll profile can be effectively maintain ed the stability by controlling the temperature of the electromagnetic stick and establishing a reasonable roll surface cooling intensity.For three typical electromagnetic stick structures,the induction heating efficiency,the energy conversion ability and the roll profile control ability are analyzed,the influence rule of electromagnetic parameter variation on the roll profile is given,and two reasonable electromagnetic stick structures are determined.Based on the reasonable structures of electromagnetic stick,the influence of dimensional changes on the roll profile is studied,and the control characteristics of the no-load roll gap when the rolls are installed in pairs are analyzed,which provide a basis for selecting the structure and size of the electromagnetic stick.Considering the heterogeneity characteristics caused by the surface quenching treatment of the roll,the influence of the different thickness and hardness surface hardened layers on the roll profile control is analyzed.The results show that the thickness and hardness of surface hardened layers has little effect on the roll crown,the roll profile curve and the average positive contact pressure,but it has a significant effect on the roll stress distribution,especially on the hardened layer of the roll center.The influence of different roll diameters on the roll profile control is analyzed,and it is found that as the roll diameter decreases,the influence area of the bulging on the roll surface decreases,the response rate of the roll crown increases,but roll crown caused by the thermal expansion increases,and the influence of roll surface cooling on the roll crown also increases.Meanwhile,the design criteria for the inner hole of electromagnetic control roll is determined that the diameter of the inner hole should be increased as much as possible on the premise of satisfying the using stiffness of the roll.Finally,the application of the segmented roll profile electromagnetic control technology in large rolls is studied,the roll profile curves of obtained by the segmented roll profile electromagnetic control technology is analyzed,the strategy of increasing the roll crown growth rate is given,and the control characteristics of the roll profile curve is dicussed,which provides guidance for the application of the segmented roll profile electromagnetic control technology.