Continuous extrusion under the large expansion ratio is an advanced forming process for manufacturing copper strip, preventing mould structure, die structure, expansion chamber structure and the shape of the billet section is important process paraments of deformation. Based on the characteristic of the forming process, the model of rigid-plastic FEM on DEFORM-3D is established and the numerical simulation of continuous extrusion forming process of the copper strip is carried. The metal flow regularity and the mean-square deviation of velocity with the different process paraments is analyzed. As the result, when using the drum form of preventing mould with promote flow angle and the die with variable calibrating strap, the mean-square deviation of velocity is 0.58. When the second extending angle is 134°, the mean-square deviation of velocity is 0.23. When size of billet is 30 x 1.64 mm2, the mean-square deviation of velocity is only 0.19.

During the continuous extrusion and rolling forming process, the microstructure evolution of copper strip was investigated by the optical microscope and transmission electron microscope. The results indicated that the grains in the centre of as-cast rod billet were squashed in the clamping zone and were elongated in the rigid mobile zone. The fibrous structure formed in the upsetting zone. In the adhesion zone, the dynamic recrystallization occurred and the shear band was found. In the right-angle bending zone, the fibrous structure, recrystallized grains and shear bands existed together. The full dynamic recrystallization occurred in the extending extrusion zone. After continuous extrusion forming, the size of the grains of copper strip was larger than that in the extending extrusion zone. After rolling, the grains in copper strip were evidently stretched along the rolling direction, which resulted in the formation of stable direction. With the increase of rolling reduction, the grains were squashed gradually. When the rolling reduction increased from 2 to 6 mm, the tensile strength increased from 250 to 400 MPa, and the elongation decreased from 48% to 13%.

The CONFORM continuous extrusion process provides outstanding features and the process has been widely used in non-ferrous metal production since it was invented. Although research and development has been quite extensive, theoretical analysis of the process has been based purely on the finite-element method, which is unable to give suitable analytical equations for calculating the stress distribution. Theoretical expressions for the contact stress distribution between the deforming material and the tools are derived in this article for the specific purpose of evaluating the load and power requirements of the machine. A simplified five sub-zone model is first established according to the different deformation characteristics in the different regions of the machine. Subsequently theoretical solutions are obtained based on simplified plasticity analysis and finally expressions are derived that can be used for calculating the load acting on the extrusion wheel and shoe. In addition, experimental verification of the theoretical results is reported.Also, much research has been carried out to investigate the process as outlined below.Cho and Jeong [5, 6] simulated the effects of the wheel diameter on the surface separation and curling phenomena as well as other significant process characteristics using the two-dimensional (2D) and three-dimensional (3D) finite-element method (FEM) for solid section aluminium products. Lu et al. [7] carried out 2D FEM simulations to determine the stress, strain, strain rate, and temperature fields for processing AA6061 aluminium alloy. Lee et al.[8] describe a 3D FEM simulation of a porthole die CONFORM extrusion process for producing aluminium multi-port-tubes used for automobile cooling systems. Reinikainen et al. [9] carried out 2D FEM simulations for CON-FORM extrusion of copper, which was assumed to take place under plane strain and isothermal conditions. Kim et al. [10] predicted the extrusion load and torque for CONFORM processing using the upper bound method.In industrial applications, there is great deal of concern regarding how to select the appropriate type and specification of a CONFORM machine in order to JPME210

Continuous extrusion expansion deforming is an advanced forming process for manufacturing copper bus-bar, die and tool structure is important effect factor of deformation. Based on the characteristics of the forming process, the model of rigid-plastic finite element (FE) on DEFORMT is established and the numerical simulation of continuous extrusion expansion forming process of the copper bus-bar is carried, The metal flow regularity and the mean-square deviation of velocity (SDV) with the different structure of expansion chamber and port hole and die assembled pattern is analyzed. The result show that when using the drum expansion chamber, the trapezium of port hole without transition surface and the die fitted in reverse, the variance of flow velocity is the minimum and deformation is the most homgeneous, the SDV is 0.62. The simulation results provide a theoretical direction for optimization design of die and tool structure of the continuous extrusion expansion forming. Keywords: copper bus-bar, continuous extrusion expansion deforming, die and tool structure optimization, numerical simulation

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