What is Red Copper?
Red copper, also known as red copper, gets its name from its purple-red color. We often refer to red copper as pure copper, but this is inaccurate. Strictly speaking, pure copper theoretically should contain close to 100% copper. Red copper is a relatively pure copper, but it is not completely equivalent to pure copper.
Red copper contains oxygen, also known as oxygen-containing copper. The copper content of red copper ranges from 99.5% to 99.99%. Red copper has excellent electrical and thermal conductivity, excellent plasticity, and is easily processed by hot and cold pressing. It is widely used in the manufacture of products requiring excellent conductivity, such as wires, cables, brushes, and copper for electrospark erosion.
The main grades of red copper are: T1, T2, and T3.
T1: Copper content is above 99.95%, with total impurities not exceeding 0.05%.
T2: Copper content is above 99.90%, with total impurities not exceeding 0.1%. T3: Copper content is above 99.7%, with a total impurity content not exceeding 0.3%.
In addition, international standards also include grades such as C11000. C11000 also has a higher copper content, generally requiring a copper + silver content of ≥99.90%.
What is oxygen-free copper?
It is generally believed that oxygen-free copper is pure copper, devoid of oxygen, deoxidizers, or residues. However, it actually still contains very trace amounts of oxygen and some impurities-very trace amounts! According to standards, the oxygen content should not exceed 0.003%, the total impurity content should not exceed 0.05%, and the copper purity should be greater than 99.95%.
As a result, oxygen-free copper, due to its extremely low oxygen content, has higher electrical and thermal conductivity, as well as better corrosion resistance and processability. Oxygen-free copper is primarily used in components for vacuum instruments and meters, such as busbars, conductive strips, waveguides, coaxial cables, vacuum seals, vacuum tubes, and transistor components. Oxygen-free copper offers excellent processability and is suitable for fine machining. Oxygen-free copper can be considered a special type of red copper.
The main grades of oxygen-free copper are: TU1, TU2, C10100, and C10200.
TU1: Purity reaches 99.97%, oxygen content no greater than 0.003%, and total impurity content no greater than 0.03%. This oxygen-free copper has extremely high purity, excellent electrical and thermal conductivity, corrosion resistance, and processability, and is free of hydrogen embrittlement. It is a high-quality copper material and is often used in applications requiring high purity and performance, such as electronics and electrical engineering.
TU2: Copper content greater than 99.95%, oxygen content no greater than 0.003%, and total impurity content no greater than 0.05%. TU2 oxygen-free copper also has excellent electrical conductivity, hot and cold working properties, and weldability, and has excellent forgeability. It is often used in the production and processing of environmental components and equipment requiring both electrical conductivity and ductility, such as conductive bars, waveguides, and electrode materials. C10100: Typically contains over 99.99% copper and less than 0.001% oxygen. This high-purity oxygen-free copper material boasts excellent electrical and thermal conductivity, corrosion resistance, low porosity, and excellent formability. It is widely used in industries such as electronics, aerospace, automotive manufacturing, and transmission machinery.
C10200: Copper content ≥ 99.95%, with total impurities ≤ 0.05%. It can be used in vacuum devices, instruments, and meters.
Appearance Differences Between the Two:
Color
Red Copper: Typically appears purple-red, hence its name. It is brightly colored and has a certain glossiness. Due to its easy oxidation in air, a dark red or dark black copper oxide film may gradually form on the surface, but the overall purple-red color remains visible.
Oxygen-free Copper: Generally appears as a purer copper color, approaching silvery white or pale yellow. Due to its extremely low oxygen content, oxygen-free copper is relatively stable in air and oxidizes much more slowly than copper, resulting in minimal surface color change and a longer-lasting, bright metallic luster.
Surface Finish:
Copper: Due to its relatively soft nature, it is susceptible to scratches and abrasions during processing and use, which may affect its surface finish. Oxidized copper may appear rough and lose some of its metallic luster.
Oxygen-free copper: It typically has a smoother, more delicate surface finish. Because oxygen-free copper is highly pure and relatively uniform, it is easier to achieve a good surface quality during processing.
Note: Distinguishing oxygen-free copper from copper by appearance is not an entirely accurate method, as the appearance of copper can be affected by various factors, including processing techniques, surface treatment, and oxidation levels. In practical applications, other methods, such as chemical analysis and physical property testing, may be used for accurate differentiation.
Differentiation in Strength and Hardness:
Copper: Relatively low in strength, low in hardness, and softer in texture. This makes it susceptible to deformation during processing and use. For example, when manufacturing thin-walled parts, the strength and hardness of copper must be considered to prevent deformation or damage during use.
Oxygen-free copper: After special treatment, it has relatively high strength and greater hardness than red copper. This makes oxygen-free copper advantageous in applications requiring resistance to certain pressures and wear. For example, in the aerospace industry, the high strength and hardness of oxygen-free copper meet the stringent material requirements of aircraft.
Oxygen-free copper exhibits superior corrosion resistance compared to red copper.
Resistivity Difference:
Red copper: At 20°C, the resistivity is approximately 0.01851 Ω·mm²/m (or 1.851×10⁻⁸Ω·m).
Red copper has excellent electrical conductivity, second only to silver among all metals, making it an important conductive material. However, its conductivity is slightly lower than that of oxygen-free copper. For example, in the electrical field, copper wires can effectively transmit current, but they may not meet the requirements in applications requiring extremely high conductivity. Oxygen-free copper: The resistivity at 20°C is approximately 0.0171 μΩ·m (or 0.0171×10⁻⁶Ω·m).
Oxygen-free copper has a higher electrical conductivity, generally exceeding 100% IACS (International Annealed Copper Standard), significantly higher than red copper. This gives oxygen-free copper unique advantages in the electronics and electrical fields. For example, in high-fidelity audio cables, oxygen-free copper ensures high-quality audio signal transmission and reduces signal loss.
Differences in thermal conductivity:
Red copper: Has excellent thermal conductivity and is often used in heat exchangers, radiators, and other heat-conducting devices. For example, in some industrial equipment, copper's thermal conductivity effectively transfers heat, improving equipment efficiency.
Oxygen-free copper: Has a slightly higher thermal conductivity than red copper and performs better in applications with extremely high thermal requirements. For example, in high-end electronic equipment, oxygen-free copper's high thermal conductivity helps dissipate heat and ensure stable operation.
Differences in applications and price:
Red copper has a wide range of applications, including general electrical, electronic, and industrial applications. Oxygen-free copper excels in high-frequency signal transmission. It can be used in high-end wires and cables, high-end electronics, vacuum tubes, and other products requiring high conductivity and signal transmission. It can also be used in fields with demanding material properties, such as communications and aerospace.
Oxygen-free copper does outperform ordinary copper in some aspects, but it cannot be universally stated that oxygen-free copper is superior to ordinary copper. The specific application scenario and requirements determine whether oxygen-free copper is superior to ordinary copper. In different applications, each has its own advantages.
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.
