关键词: 低氧铜, 氧含量, 微细铜丝, 退火, 延展性

Abstract: 2.9 mm thick thin copper strips were manufactured by cold rolling of 8 mm low oxygen copper rods with different oxygen contents (222, 288, 337 and 439 mg/kg). After annealing at 500 ℃ for 10 min, effects of oxygen content and annealing treatment on the microstructure, mechanical properties, and fracture morphology of low oxygen copper were investigated by means of tensile testing, optical microscope, scanning electron microscope, and energy dispersive spectroscopy. The results show that after cold-rolling, the microstructure changes from equiaxed grain to fiber structure. With the increase of oxygen content, the tensile strength decreases, while the microhardness increases. Recrystallized grains and twinning are formed in the thin copper strip after annealing, and the elongation improves, but the tensile strength and microhardness reduce. As the oxygen content increases, the tensile strength and elongation of annealed thin copper strips decrease, while the change in microhardness is relatively small. The tensile fracture analysis shows that the cold-rolled copper fracture is a ductile fracture. As the oxygen content increases, the shape of the dimples becomes more irregular, the size difference increases, the distribution becomes more uneven, and the fracture becomes rougher. The fracture morphology before and after annealing is similar, the necking degree is greater than that of the unannealed, indicating better plasticity. In actual production, the oxygen content is controlled within the range of 220-240 mg/kg, the low oxygen copper rod can achieve the best ductility.

Key words: low oxygen copper, oxygen content, thin copper wire, annealing, ductility