Due to the different processes for producing copper rods, the oxygen content and appearance of the produced copper rods are different. The copper rod produced by the above cited process has an oxygen content below 20ppm, which is called oxygen-free copper rod; the copper rod produced by continuous casting and rolling is hot-rolled under protective conditions, and the oxygen content is in the range of 200-500ppm, but sometimes it is also As high as 700ppm or more, under normal circumstances, the copper produced by this method has a bright appearance, commonly known as bright rod.

　　Oxygen-free copper rods are pure copper without oxygen and without any deoxidizer residues. But in fact it still contains a very small amount of oxygen and some impurities. According to the standard, the content of oxygen is not more than 0.02%, the total content of impurities is not more than 0.05%, and the purity of copper is more than 99.95%.

　　According to the oxygen content and impurity content, oxygen-free copper rods are divided into TU1 and TU2 copper rods. The purity of TU1 oxygen-free copper rod reaches 99.99%, and the oxygen content is not more than 0.001%; ​​the purity of TU2 oxygen-free copper rod reaches 99.95%, and the oxygen content is not more than 0.002%.