Oxygen-free copper rods and low-oxygen copper rods differ significantly in their core physicochemical properties, primarily in oxygen content and impurities, microstructure, conductivity, machinability, toughness, surface quality, and annealing processes. Oxygen-free copper rods have extremely low oxygen content, typically no more than 20 ppm, and few impurities; while low-oxygen copper rods have higher oxygen content, generally between 200 and 450 ppm, with oxygen often existing as copper oxide near the grain boundaries. In terms of microstructure, low-oxygen copper rods are hot-rolled, resulting in a hot-worked microstructure with finer grains; oxygen-free copper rods, on the other hand, have a cast microstructure with coarser grains.
Regarding conductivity, oxygen-free copper rods have lower resistivity; for example, the volume resistivity of grade TU1R is no greater than 0.01707 Ω·mm²/m, demonstrating superior conductivity. In terms of machinability, oxygen-free copper rods have better ductility and drawability, making them particularly suitable for drawing fine wires with diameters less than 0.5 mm; the conditions for drawing fine wires from low-oxygen copper rods are much more demanding. Oxygen-free copper rods have a uniform microstructure and better toughness; low-oxygen copper rods, due to the presence of copper oxide inclusions at grain boundaries, negatively impact toughness.
In terms of surface quality, oxygen-free copper rods have a bright surface and fewer defects; low-oxygen copper rods may contain subcutaneous oxides, affecting subsequent wire drawing processes. Due to their different microstructures, the annealing process requirements also differ. Oxygen-free copper rods, due to their coarse-grained casting microstructure and higher recrystallization temperature, require higher annealing temperatures or power.