Numerical Analysis And Microstructure Study Of Continuous Extrusion Process Of Silver-containing Copper Bars

Copper and its alloys are one of the earliest metallic materials utilized by humans.Copper bar products have become an indispensable and important part in the modern electrical industry.At present,copper bus bars are basically manufactured by continuous extrusion technology.During the continuous extrusion process,the billet experienced high temperature and complex stress conditions.Ensuring reasonable technological conditions and studying the evolution characteristics of the billet during forming process are of great significance for insuring product quality and improving economic benefits.The main work of this paper are as follows:(1)Using numerical simulation technology and based on the DEFORM-3D finite element analysis software,the temperature,equivalent stress,and metal flow rate distribution of the forming process under different process parameters(roll reduction,flash gap,wheel speed)were studied.(2)Characterization and analysis of different areas(upper,middle,and lower layers)of copper bar product cross-sections were carred out by scanning eletron microscope(equiped with EBSD and EDS)and microhardness distribution was tested.(3)Sampling the billet in different parts during processing,then the EBSD technique was used to obtain the microstructure images,statistical diagrams of the grain size and misorientation,and the inverse polar maps of the texture.The variation in the content of twins and twin boundaries were calculated,and the changes in microhardness were obtained.Conclusions based on numerical simulation and experiment are as follows:(1)The finite element analysis results show that when the roll reduction is 6mm,the flash gap is 1mm,and the wheel speed is 4rpm,the product can be extruded smoothly.The temperature of the material is within reasonable ranges.The equivalent stress and metal flow rate are also reasonable,and the mold life is longer.(2)There is inhomogeneous deformation in copper bar products.The microhardness test results also confirm the existence of this phenomenon.According to analysis,the inhomogeneous deformation may be caused by the uncoordinated rotation speed between the extrusion and coining roll.In addition,the defects such as bubble defect can be eliminated by improving the continuous casting method of copper rod raw materials and the transfer process in the workshop.(3)The results of research on the characteristics of microstructure evolution during forming show that recrystallization plays a key role in microstructure evolution during continuous extrusion.As the deformation progressing,the recrystallization develops to refine the grains and improve the microstructure.Reasonably controlling the temperature and billet residence time during the deformation process is of great improtance to make the recrystallization process fully,avoid abnormal growth of the crystal grains,and obtain a copper bar product with more uniform microstructure and excellent performance.Besides,in the initial stage of continuous extrusion,there is obvious texture in the sample,and this texture gradually disappears with the deformation process.