Oxygen in the oxygen-free copper bar (copper smelting is easy to mix with a small amount of oxygen) has a great influence on conductivity, copper used in the electrical industry must generally be oxygen-free copper. In addition, lead, antimony, bismuth and other impurities will make the crystallization of copper can not be combined, resulting in hot brittle, will also affect the processing of oxygen-free copper bar. This kind of pure copper with high purity is generally refined by electrolysis: the impure copper (i.e. coarse copper) is used as the anode and pure copper as the cathode. When the current passes through, the impurity copper on the anode gradually melts, and the pure copper gradually precipitates on the cathode. The oxygen-free copper bar thus obtained; The purity can reach 99.99%.