Numerical Simulation And Experimental Research On Drawing-Rolling Process Of Copper Clad Aluminium Bus-Bars

Copper clad aluminium bus-bars is a new type of copper-aluminium composite material.It has many advantages of excellent conductivity,thermal conductivity,small weight and low price.It is widely used in power cables,chemical and metallurgical fields.In the traditional process of preparing copper clad aluminium bus-bars,the production process is complex and costly,such as casting process,or the production product is single,which can not be mass-produced,such as drawing process.As a new technology for preparing copper clad aluminium bus-bars,the non-porous rolling technology has the advantages of good copper-aluminium composite effect,simple and efficient,but it has the problems of uneven thickness of copper cladding and unpredictable shape and size.In order to accurately prepare high-quality copper clad aluminium bus-bars,a combined process of profiled drawing process and flat roll rolling process is proposed on the basis of pass-free rolling technology.The aim is to realize the quantitative preparation of copper clad aluminium bus-bars on the basis of minimizing the change of existing passfree rolling equipment and technology.The process is divided into two main processes.The first process is to pretreat the copper clad aluminium bar blanks before rolling by drawing process to change the thickness distribution of copper cladding.The second process is to prepare the required copper clad aluminium bus-bars by multi-pass rolling process.Compared with the traditional process,the process has the advantages of low equipment requirements,large production scale,uniform thickness of copper cladding,and suitable for the production of different specifications of copper clad aluminium bus-bars.Firstly,the finite element model of copper clad aluminium bus-bars rolling process is established accurately by the method of combining experiment with simulation.Under the condition of defining roll diameter and rolling temperature,the relationship between vertical thickness ratio,reduction ratio,height-width ratio and width ratio was discussed,and regression method was used to fit the width data measured after rolling.The first pass rolling width formula of copper clad aluminium bus-bars was determined,and the width-height ratio variable was added to modify the first pass width formula,and the subsequent pass rolling width formula was obtained.Similarly,the thickness reduction of copper cladding under multiple working conditions is fitted and the calculation formula of thickness reduction of copper cladding is determined.In order to prepare copper clad aluminium busbars in accordance with national standards,rolling rules were designed by using Matlab and the whole rolling process was simulated by finite element method.Although the rolled copper clad aluminium bus-bars conforms to the requirements on the shape size and the average thickness of copper cladding,there exists the problem of uneven distribution of copper cladding thickness.Therefore,a special drawing process pretreatment method for copper clad aluminium bars before rolling is put forward to change the thickness distribution of copper cladding layer before rolling and to compensate the thinner area of copper clad layer after rolling in advance.Secondly,according to the thickness distribution of copper cladding after rolling and the design principle of drawing mold,two kinds of special-shaped drawing mold with elliptical and near-circular hole shapes are designed.The thickness distribution of copper cladding after single pass rolling,elliptical mold drawing and single pass rolling and near circular mold drawing-single pass rolling were compared and analyzed by finite element simulation method.It was determined that the elliptical mold drawing-single pass rolling process could meet the uniformity requirement of copper clad thickness,and the elliptical mold drawing and single pass rolling process was studied.By analyzing the influence of different drawing parameters on the thickness distribution of copper cladding and drawing force,the appropriate drawing process parameters were selected.Finally,according to the specifications of copper clad aluminium bus-bars,a reasonable combined drawing-rolling process is designed and the whole process is simulated by finite element method.Finally,the width is 60.39 mm and the thickness of copper cladding is between 0.64 and 0.78 mm,all within the allowable range of standard tolerance.The rationality of the calculation formula and the feasibility of the process were preliminarily verified,which played a guiding role in actual production.