Copper and copper alloys are a class of key materials with important applications. Due to its excellent thermal conductivity, electrical conductivity, ductility, corrosion resistance, etc., copper is a necessary material for certain applications in aerospace and weaponry.
In additive manufacturing, the application of copper materials is relatively late, but in recent years it has shown a rapid development trend. In particular, the application of copper alloy additive manufacturing in the defense and military industry has continuously made important progress, which has promoted the development of copper material additive manufacturing.
In the past two years, the additive manufacturing industry has clearly felt the increase in demand for copper alloys, and new users continue to develop copper alloy additive manufacturing applications. The materials have also shifted from the early easy-to-shape cast tin bronze to pure copper and various high-strength and high-conductivity coppers. . According to a research report, during 2019-2027, the global copper additive manufacturing market will grow at a compound annual growth rate of 51%. Although there are still many process and material problems in copper alloy printing, it is foreseeable that copper will have a place in metal additive manufacturing.
Application status of copper alloy materials at home and abroad
With the rapid progress of the high-tech industry, new materials are developing in the direction of ultra-high performance, high purity, and high iteration , which puts forward higher requirements for the integration, functionality, miniaturization, and reliability of related products. Advanced copper and copper alloys are used as core conductor materials, which are widely used in electronic information industry VLSI lead frames, electronic countermeasures, radars, high-power microwave tubes for defense equipment, high-pulse magnetic field conductor materials, overhead wires for high-speed rail transit, large Power frequency modulation and speed regulation asynchronous traction motor guide bars and end rings, resistance welding electrodes for new energy vehicles, battery materials, charging pile elastic materials, continuous casting machine molds for metallurgical industry, electric vacuum devices, switch contact bridges for electrical engineering and various Kind of wires and so on.
At present, many well-known foreign additive manufacturers have included copper materials in their product catalogs. More representatively, EOS announced the data manuals of pure Cu and CuCrZr in 2020, and launched the AMCM (EOS subsidiary, production customized equipment, Additive Manufacturing Customized Machine) version of two types of materials in 2021. SLM Solutions has successively launched CuSn10 and CuCrZr product data. In 2019, the company launched CuNi2SiCr products that take into account both strength and electrical and thermal conductivity, which can be used in molds and electrical fields and become a major product in additive manufacturing of copper alloy materials.
Material manufacturers TLS Technik, m4p, Sandvik, Makin and other companies have announced their own additive manufacturing copper alloy products. At present, copper and copper alloy materials for additive manufacturing are concentrated in pure Cu, CuSn10, CuCrZr and CuNi2SiCr. Although CuNiSn, CuCr, CuCrNb, CuAlFeNi and other materials also have relevant additive manufacturing research and applications, the degree of application is not as good as the first four types of products. Youyan Powder New Material Co., Ltd. (abbreviated as “Youyan Powder”, stock code 688456) is the largest copper powder supplier in China, with an annual sales of over 30,000 tons of copper and copper alloy powder. Its subsidiary, Beijing CommScope Xiwei has carried out the research and application of copper and copper alloy powder for additive manufacturing earlier in China. At present, it has formed a relatively complete series of special copper and copper alloy powder products for additive manufacturing, including pure Cu, CuSn10, CuCrZr, CuNi2SiCr, CuAlFeNi, etc., have achieved important applications in aerospace, Mold, electrical and other fields.
1. Pure Cu
Compared with copper alloys, the advantage of pure Cu is its electrical and thermal conductivity, because all kinds of copper alloys will inevitably lose electrical and thermal conductivity after adding elements to copper. Since pure copper has a low absorption rate at the conventional 1064nm wavelength, the so-called red wavelength, and it is not easy to achieve compactness, pure Cu printing has always been a problem. The current solution is to use a short-wavelength laser, such as TRUMPF’s 515nm green laser device, and the other is to increase the power, such as EOS’s AMCM device equipped with a 1Kw laser for pure copper printing. No matter what type of equipment is used for printing, to obtain high density or high electrical and thermal conductivity pure copper parts, the raw material powder needs to maintain high purity while also having powder characteristics that are easier to achieve densification, such as reasonable particle size distribution and flow Good performance and high loose packing density. As far as the preparation of pure copper powder is concerned, maintaining high purity of the material while maintaining high sphericity is the goal.
As a cast tin bronze, CuSn10 is easy to shape, and many models or crafts involving copper materials are printed with CuSn10. CuSn10 alloy has high strength, excellent wear resistance and corrosion resistance. It can be used to manufacture wear-resistant parts such as blades and gears, but its electrical and thermal conductivity is not high. Therefore, CuSn10 is generally not used for electrical or thermal conductivity requirements. CuSn10 is a conventional product in the current additive manufacturing of copper alloy materials.
Rocket motors are a typical application scenario for copper alloys. The material requirements for engine lining and related parts are extremely high. On the one hand, due to the extremely high combustion temperature of the combustion chamber (over 3000°C), on the other hand, high temperature, high pressure and high-speed gas have strong corrosion on the materials. CuCr alloy is a typical precipitation-strengthened copper alloy, and the addition of Zr element can promote the precipitation of Cr phase and improve the distribution of precipitated phases. At the same time, the copper-zirconium compound formed by Zr and Cu can play a role of precipitation strengthening. Therefore, CuCrZr alloy mechanics It has excellent performance and can be used in the manufacture of rocket engine parts. In recent years, domestic aerospace units have carried out more research and development work on the additive manufacturing of rocket engine thrust chamber parts. CuCrZr is currently an optional material. It is worth mentioning that copper alloy materials for rocket engine parts are still being updated and iterated. CuZr, CuCr, CuAgZr, CuCrNb and other materials have successively applied researches, especially the GRcop-42 which is being verified by NASA in the United States. (Cu-4Cr-2Nb at%), it is expected to upgrade the rocket engine combustion chamber material to a new level.
SLM Solutions launched the CuNi2SiCr copper alloy material product in 2019. This material is a heat-treatable hardenable alloy with high strength and a balanced combination of electrical conductivity and thermal conductivity. At the same time, the alloy includes nickel and silicon components, which has high resistance Corrosion and wear resistance. CuNi2SiCr itself is not a new component. This material corresponds to the American Standard C18000 alloy. SLM Solutions took the lead in using this material in additive manufacturing and carried out material identification and parameter verification work, adding an important member to the additive manufacturing copper alloy family . The strength of CuNi2SiCr after heat treatment is significantly higher than that of CuCrZr and other materials, while maintaining a certain degree of thermal conductivity and electrical conductivity. It has been able to meet some mold manufacturing requirements and conductive parts requirements, so it will have important applications in molds and electrical fields.
The R&D Trends and Problems of my country’s Advanced Copper Alloy Materials
(1) Technology research and development trends
In recent years, the overall level of my country’s high-performance copper alloys and their preparation technology has made considerable progress. The types of high-performance copper alloy products with independent intellectual property rights have been increasing, and the level of installed copper alloy materials processing has approached the international advanced level. The development trend of R&D and industrialization of advanced copper alloy materials presents the following characteristics.
(1) Development from a single performance requirement to a multifunctional characteristic requirement. For example, copper-based materials with high thermal conductivity and high electromagnetic shielding performance should meet the demand for conductor materials in high-precision fields such as pulsed strong magnetic field systems and particle acceleration electromagnetic transmitters; 380 km/h high-speed railway power grid contact line In addition to high electrical conductivity, it should also have higher strength, wear resistance and fatigue resistance; copper alloys for super-large-scale integrated circuits require high-strength, high-conductivity, heat resistance, bending resistance, and easy etching characteristics.
(2) Copper processing materials are developing in the direction of thinness, thinness, length and high precision. The demand for ultra-fine wires, ultra-thin ribbons, thin-walled tubes, ultra-long tubes, ultra-long tapes, threaded tubes, special-shaped tubes, special-shaped rods, special-shaped belts and other products continues to increase. For example, the lead frame reflects the multi-legged and high-density , Ultra-thin, miniaturization development trend.
(3) High purification of copper. The copper content of industrial copper is increased from 99.9% to 99.95%, and then to 99.99% or even higher, in order to improve the electrical and thermal conductivity of the material as much as possible. Ultra-pure copper with a copper content of 99.999 9% will minimize the impact of impurities on electrical and thermal conductivity.
(4) Material composite. The potential of a single material strengthening method is limited, and the use of composite methods to further improve the comprehensive performance of copper has become a research hotspot. For example, adding second-phase particles, whiskers or fibers to copper alloys to strengthen the copper matrix and develop new multifunctional copper-based composite materials, which are important for the design theory of high-performance copper alloys and practical applications in the high-tech fields. value.
(2) Problems faced
Although my country is the world’s largest producer of copper alloy materials, it is still not a strong country in copper alloy materials. my country’s aerospace, electronic information, marine engineering, high-end equipment and many other high-tech fields of high-performance copper alloys that are urgently needed still rely on imports; there are many copper alloy material manufacturers, low industrial concentration, weak product competitiveness, and meagre industry profits. , Unable to support the development of high-tech industries. The main issues involved in the copper alloy material industry are as follows.
(1) There are few varieties and grades of high-performance copper alloy materials, and the overall performance of some high-performance copper alloys is generally lower than that of similar imported products, such as the independently developed and produced Cu-Ni-Si and Cu-Cr-Zr lead frame strips. few.
(2) The stable production capacity of large-scale and high-quality copper alloy products needs to be improved urgently. For example, the performance stability, surface quality, and comprehensive finished products of high-precision elastic copper alloy strip products still need to make breakthroughs.
(3) The processing of high-performance copper alloys has serious environmental pollution and serious waste of resources; the efficient and short-process preparation technology is not yet mature, and the product quality and performance need to be improved.
(4) The lack of independent manufacturing technology for some high-end production equipment limits the development of new products. For example, most high-precision foil production equipment relies on imports.
(5) Some high-end copper alloy materials lack independent intellectual property rights and a public R&D platform, and the construction of databases on material performance, production technology, standards and specifications is lagging behind.
(6) The preparation technology of ultra-high purity, ultra-low oxygen content oxygen-free copper large-size homogenization still needs to be further improved, and the preparation technology of high-precision, large-diameter and long-life corrosion-resistant copper-nickel alloy needs to be deepened.
Compared with products such as titanium, aluminum, and high-temperature alloys, the additive manufacturing of copper and copper alloys is still immature. EOS has introduced the concept of similar technology reserve level (TRL) for material products in 2019. At present, two types of copper materials are marked as level 3, which belongs to the verification level, while products such as IN718 and AlSi10Mg are generally level 7-9. At this stage, additive manufacturing has gradually shifted from model verification to product manufacturing. Additive manufacturing materials will enter the stage of selecting or designing materials based on applications. The update iteration of copper and copper alloy materials is more obvious. It is foreseeable that with the continuous advancement of processes and materials, the application of additive manufacturing of copper materials will rise to a new level.
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