Producing large-scale industrially applicable high-precision copper strips by continuous extrusion with a novel U-shaped die

Abstract

Copper strips with a cross-section of 420 mm × 14 mm were manufactured by continuous extrusion with a novel U-shaped die, which extends the thickness-width ratio of copper strips produced by this technique. The U-shaped die was designed and optimized by Deform-3D finite element simulation during continuous extrusion by varying different thicknesses D, external diameters R1, and the opening angle between the straight side and axis of symmetry θ, of the product. The optimized dimensions of the die are with D=14 mm, R1=77 mm, and θ=5°. The simulated results indicated that an equal distance from the billet to each point of the U-shaped die can facilitate the metal forming, thus decreasing the torque force of the wheel and the temperature of the product. The simulated results were then verified by the temperature measuring and torque force calculating at/for extruded U-shape and flat strips. The experimental results showed that the torque force of the wheel and temperature of the U-shaped strip are lower than those of the flat strip, although the cross-section of the flat strip is much smaller (300 mm × 12 mm). In addition, the copper strip produced with the U-shaped die exhibits a more uniform microstructure and finer grain sizes in comparison with those produced with the flat die. And the lamination defects in the U-shaped strip are fewer and smaller in size. These findings demonstrate that the U-shaped die is superior to the flat die in producing large-scale copper strips. Hence, the present work provides a new concept to design and optimize the die structure for continuous extrusion forming in production.