Research On Roll System Parameter Matching Based On Improving The Shape Control Performance Of 6HI Cold Rolling Mills For Flat Products

Metal plates and strips are closely related to the industrial production,living conditions,and national defense.High-precision rolling mills for flat products are the key equipment.With the increasing prominence of resources and environmental issues worldwide,AHSS strips have drawn much attention in recent years.Global major steelmakers are making great efforts to develop AHSS strips and their deep processing technology,especially those used to make automobiles.There are two main rolling mill types applied to the domestic production of cold-rolled strips — six-high HC mills and UCM mills.But as a result of the increasing roll separating force and flatness control complexity,it has become harder and harder for these mills to adapt the manufacture of relatively thin cold rolled AHSS strips.There will be many problems such as higher cost of investment if Sendzimir mills or other kinds of cluster mills are used.Optimization and upgrades of the roll systems may not only effectively extend the service lives of the existing domestic production lines,but also have a good performance in producing high quality AHSS strips.Those indicate that this monographic research has an important practical background of engineering and it is an urgent issue to find out the effects of the rolling mill types and roll system parameters on shape control characteristics in the production of AHSS strips as well as the relevant mechanisms.According to the actual situations of the production,a model suitable for cold rolling of AHSS strips is established to calculate the minimum rolling gauge.In addition to productivity,the exit elastic zone is taken into account as well as the entrance elastic zone in the model.The calculating for the permissible work roll diameter limited by the minimum rolling gauge and the available maximum rolling pressure of the last rolling stand of a medium-width strip tandem cold rolling mill unit is carried out.The restrictive effects of the housing window,torsional strength of the driving roll,lateral stiffness,and the contact pressure between rolls on the roll diameters are analyzed,respectively.The content is helpful for determining the essential boundary conditions in optimal matching research of roll system parameters.Considering the relationships between rolls and moving strips as well as the interaction between the vertical movement of the roll system and the horizontal movement of the work roll,a multi-parameter coupling dynamic model of six-high tandem strip rolling mills is established.The influences of different roll diameters on the dynamic stability of the work roll are analyzed in cold rolling of AHSS strips.A theoretical model of three-dimensional rolling for flatness calculation and a quantitative model for shape controllability of rolling mills for flat products are developed,which can be used for cold rolling of AHSS strips.An example application is presented to conduct the adjustment characteristic analysis of the 900 UCM stand of a tandem cold rolling mill for its three fast acting flatness actuators.The validity of the shape computational model is analyzed with the help of the 650 UCM pilot platform.In order to validate the coupled dynamic model for six-high tandem strip rolling mills,a field test on the dynamic characteristics of a 900 UCM rolling mill is carried out.The sensitivities of the shape controlling efficiency of AHSS strips to the diameters of the work roll and the intermediate roll are computed and discussed,respectively.Roll system collocation parameters of six-high rolling mills are put forward and the sensitivity of the quarter crown to roll system collocation parameters is analyzed and discussed.Based on the built model for evaluating shape controllability of rolling mills for flat products,the effects of roll system collocation parameters of six-high rolling mills on the shape control capability and stability are systematically investigated for high strength steel strips and the influence mechanisms are analyzed.The effects of roll system collocation parameters on the non-control point of UCM mills are studied.The shape control characteristics of the mill during cold strip rolling with different deformation resistance and different roll system collocation parameters are calculated.The effects of roll system collocation parameters on the contact pressure between rolls during strip rolling of AHSS are analyzed.Shape controllability enhancement oriented optimal matching and design principles for the roll system of the UCM mills producing AHSS strips are proposed,and an example is given.What the present dissertation discusses would give some useful and meaningful references for the design of AHSS cold strip rolling mills as well as the reconstruction and upgrades of the existing cold rolling production lines aimed at adapting the changes in demands of the steel market.