Based on oxygen and impurity content, oxygen-free copper rods are further classified into TU1 and TU2 grades. TU1 oxygen-free copper rods achieve a purity of 99.99%, with an oxygen content not exceeding 0.001%; TU2 oxygen-free copper rods achieve a purity of 99.95%, with an oxygen content not exceeding 0.002%.
Due to differences in the production processes for copper rods, the oxygen content and surface appearance of the finished products vary. Copper rods produced by the upward drawing process have an oxygen content of less than 20 ppm and are therefore referred to as oxygen-free copper rods; in contrast, copper rods produced via continuous casting and rolling are hot-rolled under protective atmospheres, with oxygen contents ranging from 200 to 500 ppm—though they can occasionally exceed 700 ppm. In general, copper rods manufactured using this method exhibit a bright, polished surface and are commonly known as “bright rods.”
Oxygen-free copper rod is pure copper that contains no oxygen and no residual deoxidizers. In practice, however, it still contains trace amounts of oxygen and certain impurities. According to the relevant standards, the oxygen content shall not exceed 0.02%, the total impurity content shall not exceed 0.05%, and the copper purity shall be greater than 99.95%.
Based on oxygen and impurity content, oxygen-free copper rods are further classified into TU1 and TU2 grades. TU1 oxygen-free copper rods achieve a purity of 99.99%, with an oxygen content not exceeding 0.001%; TU2 oxygen-free copper rods achieve a purity of 99.95%, with an oxygen content not exceeding 0.002%.
Method of distinction
Both imported and domestically produced oxygen-free copper rods are available; however, imported products no longer offer any significant advantages. Once the copper rod is manufactured, the differences between the two are minimal. As long as high-quality copper billets are selected and production control is stable, even domestically produced equipment can produce copper rods that can be drawn down to 0.05 mm in diameter.
Oxygen-free and low-oxygen copper rods can be readily distinguished by their oxygen content: oxygen-free copper has an oxygen content of no more than 10–20 ppm, though some manufacturers can only achieve below 50 ppm, whereas low-oxygen copper rods typically range from 200 to 400 ppm. High-quality low-oxygen rods generally maintain an oxygen content of around 250 ppm. Oxygen-free rods are usually produced by the upward drawing process, while low-oxygen rods are made via continuous casting and rolling. Compared with each other, low-oxygen rods are better suited to enameled wire performance—in terms of flexibility, springback angle, and winding characteristics. However, low-oxygen rods demand more stringent drawing conditions; for instance, when drawing a 0.2-mm fine wire, a standard oxygen-free rod may be drawable under suboptimal conditions, whereas a high-quality low-oxygen rod is likely to break. Conversely, under optimal drawing conditions, the same low-oxygen rod may even be drawn down to 0.025 mm, while a typical oxygen-free rod can usually only be drawn to 0.1 mm at most. Of course, for the very finest grades, such as 0.02 mm, one must rely on imported oxygen-free copper rods. Some companies have attempted to treat low-oxygen rods by peeling the surface in order to draw 0.03-mm wire; however, audio cables generally prefer oxygen-free rods, which is related to the fact that oxygen-free rods are single-crystal copper, whereas low-oxygen rods are polycrystalline copper.
About Us
Hebei Zhongmai Metal Wire Co., Ltd.
Hebei Zhongmai Metal Wire Co., Ltd. was established in 2012 and is located on Landu Avenue in Jiajiakou Town, Ningjin County, Xingtai City. It is conveniently situated adjacent to the Ningjin-Dongqing-Yin Expressway and National Highway 308, with a well-developed transportation network that provides convenient support for logistics, transportation, and business expansion.
The company covers a total area of 26,680 square meters and currently employs over 80 people. Relying on its large-scale production base and a team of highly skilled professionals, the company has established an efficient and stable operational system. As a leading enterprise in the metal wire industry, the company has been deeply engaged in this sector for many years and has developed an integrated “production + sales” business model. Its core products include processed items such as copper wires, aluminum wires, stranded wires, and aluminum alloy conductors.