First, the inhalation and desorption of oxygen and its state of existence
Generally, the cathode copper oxygen content of copper rod production is 10-50 ppm, and the solid solubility of oxygen in copper at room temperature is about 2ppm. The oxygen content of a low oxygen copper rod is generally 200 (175)-400 (450) ppm, so the oxygen is inhaled as a liquid form of copper, while the oxygen in an anaerobic copper rod of the up-drawing method is reversed. After prolonged storage in the liquid state of copper, the rods typically have oxygen levels below 10-50 ppm and as low as 1-2 PPM. From the perspective of tissue, the oxygen content of low oxygen copper rod is reduced and removed. The presence of copper oxide inclusions at grain boundaries has a negative effect on the toughness of the materials. The oxygen content of anaerobic copper is very low, so the microstructure of this copper is uniform single-phase structure, which is conducive to toughness. Pores in oxygen free copper rods are not common, but they are common defects in low oxygen copper rods.
Two, the difference between hot rolling structure and casting structure
Because of hot rolling, the structure of the low-oxygen copper rod belongs to the hot-working structure, the original as-cast structure has been broken, and the recrystallization of 8mm rod has appeared, while the oxygen-free copper rod belongs to the as-cast structure with coarse grains. This is the intrinsic reason for the higher recrystallization temperature of oxygen-free copper, which requires a higher annealing temperature. This is because recrystallization occurs near the grain boundaries. The grains of anaerobic copper rods are coarse, even up to a few millimeters, so the grain boundaries are small. Even when deformed by drawing, grain boundaries are still small compared to low oxygen copper rods, thus requiring higher annealing power. The requirement for successful annealing of anaerobic copper is that the annealing power of the first annealing should be 10 to 15% higher than that of the same low-oxygen copper when the wire is pulled from the rod but the tissue has not yet been cast. After continuous drawing, the late annealing power should have enough margin, and different annealing processes should be carried out for low-oxygen copper and anaerobic copper to ensure the softness of the products in process and the finished wire.
Three. Inclusions, oxygen content fluctuations, surface oxide differences and possible hot rolling defects.
Bzchcp3-" > The drawing performance of anaerobic copper rod is better than that of low-oxygen copper rod in all wired diameters. In addition to the above reasons, the oxygen free copper rod has fewer inclusions, stable oxygen content, no defects that may be caused by hot rolling, and the thickness of the oxide layer on the rod surface can reach 15A or less. In the process of continuous casting and rolling, if the process is not stable and oxygen monitoring is not strict, the unstable oxygen content will directly affect the performance of the bar. If the oxide on the surface of the rod body can be made up in the continuous cleaning of the subsequent process, what is more troublesome is that there is quite a lot of oxide under the skin, which has a more direct impact on the broken wire. So, in order to reduce wire breakage, it is sometimes necessary to resort to the last resort of peeling the copper rod, or even a second peel. The goal is to remove subcutaneous oxide.
Fourthly, the toughness of low oxygen copper rod is different from that of no oxygen copper rod.
Both can be drawn to 0.015mm, but the distance between the low temperature grade oxygen free copper wires in the low temperature superconducting wire is only 0.001mm.
Fifth, there are economic differences from rod making materials to wire production.
High quality raw materials are needed to manufacture anaerobic copper rods. Generally, when drawing copper wire with diameter > 1mm, the advantage of low-oxygen copper rod is obvious, and the advantage of anaerobic copper rod is drawing diameter.
6. The wire making process of low oxygen copper rod is different from that of no oxygen copper rod.
The wire making process of low oxygen copper rod cannot be copied from the wire making process of no oxygen copper rod, at least the annealing process of the two is different. Because the softness of wire is deeply affected by material composition, rod making, wire making and annealing process, it is not simple to say that low oxygen copper or no oxygen copper is soft and hard.