Study On Flattening Process Of Pure Copper Based On U-profile

The consumption of copper sheet and strip accounts for about one third of the total consumption of copper processing materials,and it is one of the important products with the highest technical content in the field of copper processing.The demand for high-precision copper sheet and strip is growing rapidly in recent years.Due to the cumbersome processes,low efficiency,the need for milling,and the inability of continuous production,the traditional process method for producing plates and strips does not have obvious advantages in producing high-precision sheets and strips.The emergence of continuous extrusion technology provides a new choice for the production process of sheet and strip.Compared to the traditional processes,continuous extrusion has the advantages of no heating,low energy consumption,simple process,and high yield of products,continuous production and many other advantages.However,when the continuous extrusion process is used to directly prepare large aspect ratio plates,defects such as flash and waves are prone to occur.Therefore,a new production method of continuous extrusion U-profile combined with flattening process to obtain large aspect ratio plates is proposed.The flattening process is an important part of the continuous extrusion technology to prepare wide sheets,which has a great influence on the sheet and strip accuracy and product performance.Therefore,in this paper,the methods of numerical simulation,theoretical calculation and experimental analysis are used to analyze the flattening forming process of the pure copper U-profile.The main conclusions are as follows:(1)The flattening process of pure copper U-profile with different thicknesses and widths is simulated,and the results show that the equivalent stress and strain of the thickness of 12 mm are the smallest,followed by the thickness of 14 mm,the stress and strain differences between the inner and outer surfaces of the plate and the flattening force are small.When the thickness of the plate exceeds 14 mm,the equivalent strain value increases significantly,the equivalent effect at 14 mm becomes 0.1,and as the thickness increases,the strain reaches around 0.2.Therefore,the range of thickness of the flattened U-profile is reasonable at12mm～14mm;when the sheet width is ranging from 420 mm to 500 mm,the equivalent strain is the smallest,about 0.1,and the maximum strain of the 340 mm sheet is about 0.22.As the width increases,the overall force of the plate is more uniform,and the flattening force is reduced.Therefore,it is reasonable for the width of the plate is more than 420 mm and the fillet radius is more than 70 mm.(2)The finite element simulation of the step-by-step continuous flattening forming process of U-profile is carried out,and the equivalent stress field and equivalent strain field are analyzed.The introduction of round rollers in the original flattening mechanism reduces the maximum strain on the edge from 0.175 to 0.09.The load on the pressing die is reduced by about 100 KN.At the same time,the indentation on the edge of the sheet disappears,and the sheet is flattened easily for reducing thickness further.The difficulty of the subsequent finishing process is eliminated.(3)Based on the elastic-plastic deformation theory combined with the deformation characteristics of flattening,the flattening mechanical model is established in this study.According to the optimized results of variable section die,the flattening force are obtained by formulas of 4-15 and 4-16,and the flattening force calculation results were compared with the finite element simulation results.The two trends are basically the same,the calculation results are relatively accurate.(4)The flattening strain and flattening force were measured by the simplified flattening test.The strain in the arc area is about 0.12,the flattening force in the stable stage is basically consistent with the results of theoretical calculation and numerical simulation.the microstructure of the plate has no obvious change after flattening.There is obvious work hardening in the arc area,the hardness of the upper surface of the arc area increases from 74 HV to 92 HV,while the changes of hardness is very small at other positions.Pure copper U profiles can be flattened to the desired effect.