Oxygen-free copper and low-oxygen copper are definitely not the same material. They have very different properties, and if you carefully distinguish them based on appearance, you can also notice some differences.
First, the production processes of oxygen-free copper and low-oxygen copper are different, as you can tell from the name. The main difference between the two is the oxygen content... At this point, someone said, "I know one contains oxygen and the other doesn't." While this sounds correct, it's actually wrong!
Although it's called oxygen-free copper, this material does contain oxygen! (The content is just very small, negligible, but it's not oxygen-free.) The manufacturing processes of oxygen-free copper and low-oxygen copper are different, so there are also certain differences in their performance. In terms of appearance, oxygen-free copper has a shinier appearance! So, when you encounter both materials, the oxygen-free copper material generally has the brighter look.
Back to the copper rod. As mentioned earlier, due to the different production processes, the oxygen content and appearance of the copper rod also vary. Copper rod produced using the top-drawing method, with proper processing, has an oxygen content below 10 ppm and is called oxygen-free copper rod.
Copper rod produced using the continuous casting and rolling process is hot-rolled under protective conditions, resulting in an oxygen content within the 200-500 ppm range, but can sometimes reach levels as high as 700 ppm or above. Generally, this method produces copper with a bright, low-oxygen copper rod appearance, sometimes also called polished rod. Of course, there's also the dip-coating method, which offers even higher quality.
Oxygen-free copper rod is produced using either imported or domestically produced equipment, but the difference in the final product is not significant. With good copper plate selection and stable production control, domestically produced equipment can also produce copper rod with a 0.05 tensile strength.
Oxygen-free and low-oxygen copper rod can be easily distinguished by their oxygen content. Oxygen-free copper has an oxygen content below 10-20 ppm, but some manufacturers currently only achieve below 50 ppm. Low-oxygen rod has an oxygen content of 200-400 ppm, while good rod generally has an oxygen content of around 250 ppm. Oxygen-free rod is generally produced using the top-drawing method, while low-oxygen rod is continuously cast and rolled. Compared to the two products, low-oxygen rod is more suitable for enameled wire properties, such as flexibility, springback angle, and winding performance. However, low-oxygen rod is more demanding in terms of wire drawing conditions! For the same 0.2mm thin wire, if the drawing conditions are poor, ordinary low-oxygen rod will be able to draw, while good low-oxygen rod will break.
However, if the drawing conditions are good, the same rod may be able to draw to 0.05mm, while ordinary low-oxygen rod can only draw to 0.1mm at most. Of course, the thinnest wires, such as 0.02mm, must rely on imported oxygen-free copper rod. Some companies are currently experimenting with stripping low-oxygen rod to draw 0.03mm thin wire, but I'm not very clear about this. Oxygen-free copper is generally preferred for speaker cables. This is because oxic-free copper is made of single-crystal copper, while low-oxygen copper is made of polycrystalline copper.
Both low-oxygen copper and oxic-free copper are used in electrical applications, such as wire and cable, enameled wire, flat wire, and copper busbars. Their applications are largely the same. The difference lies in their oxygen content. The national standard specifies an oxygen content of less than 450 ppm for low-oxygen copper, while less than 20 ppm for low-oxygen copper.
Oxygen-free copper has higher resistivity and processing performance than low-oxygen copper, so high-quality electrical materials generally use oxic-free copper. For example, when making enameled wire, oxic-free copper undoubtedly produces lower resistance. When used in motors, heat generation is undoubtedly better than that of low-oxygen copper. Therefore, quality-conscious manufacturers prefer oxic-free copper as raw material.
Furthermore, low-oxygen copper makes it difficult to draw wire thinner than 0.5 mm, while oxic-free copper offers much better processing performance.
Thus, the current trend is: low-oxygen copper is used for large-scale electrical products with low resistance requirements, while oxic-free copper is used for small-scale products with high resistance requirements. Everyone knows that oxygen-free copper rod is superior, but does this superior performance mean a higher price?
Currently, the top-drawing method is the primary method used to produce oxygen-free copper rod in China. This mainstream process offers advantages such as a short process flow, high yield rate, low cost, and minimal investment. Therefore, the price of oxygen-free copper rod is not significantly higher than that of ordinary copper rod. Furthermore, the production process of oxygen-free copper has undergone numerous improvements over the past 20 years. A mature oxygen-free copper rod manufacturer can easily bring the cost of oxygen-free copper rod to a similar level as that of ordinary copper rod.
The company has a cluster of leading copper processing production lines in China, including:
German imported precision copper tube production line (annual output of 30,000 tons)
Japanese technology copper foil rolling line (thinnest up to 6μm)
Fully automatic copper bar continuous extrusion line
Intelligent copper sheet and strip finishing mill unit
Digitalized control and management of the whole production process is realized through MES system, and the dimensional accuracy of the products can reach ±0.01mm.
