1. High purification: The main purpose of high purifica […]
1. High purification: The main purpose of high purification is to improve the electrical and thermal conductivity of the material as much as possible. The copper content of industrial copper ranges from 99.90% to 99.95%, and then to 99.99% (4N) or even higher. For example, ultra-pure copper containing 99.9999% (6N) copper has stricter impurity content requirements. For example, the oxygen (O) content is reduced from 0.01%~0.05% to 0.001%~0.006%, until 0.0002%~0.0003%. Minimize the impact of impurities on electrical and thermal conductivity. Typical application examples are high-purity copper for network transmission connecting wires, high-purity oxygen-free copper for electric vacuum devices, precision guidance and high-fidelity signal transmission, and single crystal copper and ultra-pure copper for superconductors.
Compared with polycrystalline copper, the tensile strength of single crystal copper has decreased by 24.71%, the elongation has increased by 2.39 times, the reduction of area has increased by 4.14 times, and the resistivity has decreased by 31.7%, which is less than 1.72×10-8Ω·m , Its oxygen content is less than 5×10-6, hydrogen content is less than 0...5×10-6, and its density is more than 8.92t/m3.
Another aspect of the development of copper alloy materials in the direction of high purification is that the high purity of the copper alloy matrix is required in the microalloyed copper alloy to ensure that the material has a higher comprehensive performance.
2. Microalloying: The purpose of microalloying is to sacrifice the least electrical and thermal conductivity in exchange for other properties, such as a substantial increase in strength. Such as adding about 0.1% of iron (Fe), magnesium (Mg), tellurium (Te), silicon (Si)), silver (Ag), titanium (Ti), chromium (Cr) or zirconium (Zr), rare earth elements, etc. , Can improve its strength, hardness, resistance to softening temperature or cutting ability. Microalloyed copper is currently one of the hottest developments of copper alloy materials. Aerobic toughened copper and high-strength and high-conductivity copper alloys are the most important microalloyed copper.
The concept of aerobic copper is that relative to oxygen-free copper, its copper content is more than 99.90%, which is equivalent to general pure copper, but its oxygen content is controlled at 0.005%~0.02%, and the conductivity can be above 100% IACS. . This is because the appropriate amount of oxygen has a certain oxidation and chemical cooperation effect on the impurity elements between the crystals, which purifies the matrix to a certain extent. The biggest feature of aerobic copper production is the low cost of its raw materials, and the use of low-grade red copper materials to produce aerobic copper materials equivalent to high electrical and thermal conductivity.
High-strength and high-conductivity copper alloys are favored by material science and technology workers from all over the world due to their good comprehensive properties. They are the fastest growing type of copper alloys in recent years. The microalloying elements mainly include: P, Fe, Cr, Zr, Ni, Si, Ag, Sn, Al, etc. The representative alloy systems mainly include Cu-P, Cu-Fe-P series, Cu- Ni-Si series, Cu-Cr, Cu-Cr-Zr series, Cu-Ag, Cu-Ag-Cr, Cu-Ag-Zr series, Cu-Sn series, etc., as well as various rare earth-added alloy systems. The sum of the content of other components in the alloy can be at least 0.01%~0.1%, and the highest is generally not more than 3%. The common feature is that the material has high-strength and high-conductivity properties.
3. Complex multi-alloying: In order to further improve the strength, corrosion resistance, wear resistance and other properties of copper and its alloys, or to meet the requirements of certain special applications, it is added to the existing bronze, brass, etc. Five-element, six-element and other components, to achieve different functions of material such as high elasticity, high wear resistance, high corrosion resistance, and easy cutting. Multi-component (four or more components) alloying to become copper alloy development Another hot topic in China, new complex alloys are emerging in endlessly. Typical alloys include multi-element manganese brass, silico-manganese brass, boron-added tin brass, and lead-free free-cutting copper alloys. The common feature is high strength and high toughness, and the tensile strength is generally above 600~700MPa. For example, the new manganese brass HMn59-2-1-0.5 (Cu: 58%~59%, Mn: 1.8%~2.2%, Al: 1.4%~1.7%, Fe: 0.36%~0.65%, Si: 0.6% ~0.9%, Sn: 0.1%~0.4%, Pb: 0.3%~0.6%, Zn balance), the strength of the control tube is more than 600MPa, the elongation is more than 20%, and the hardness HB is more than 180. Aluminum brass HAl64-5-4-2 (Cu: 63.5%~65.5%, Al: 4.5%~6.0%, Mn: 3.0%~5.0%, Fe: 2.0%~3.0%, Pb: 0.2%~1.0% , Zn allowance), its strength reaches above 750MPa, and the hardness HB exceeds 220. New aluminum bronze QAl9-5-1-1 (Cu: allowance, Al: 8.0%~10.0%, Ni: 4.0%~6.0%, Mn : 0.5%~1.5%, Fe: 0.5%~1.5%), its strength is 650MPa, the yield strength is 400MPa, and the elongation is more than 14%. Using these materials to manufacture automobile synchronizer gear rings, high-pressure pump friction pairs or electrode copper wedges, its life span is one to several times longer than that of ordinary brass or bronze.
In recent years, as people's awareness of environmental protection has increased, environmental protection has become the theme of the development of world civilization. People pay more attention to the influence of harmful elements such as lead, beryllium, cadmium, and arsenic. The development of environmentally friendly copper alloy materials such as lead-free easy-cutting brass, beryllium-free high-elasticity copper alloy, and arsenic-free corrosion-resistant copper alloy has become important for copper alloy materials. One of the development directions.