ABSTRACT: This paper is aimed at the typical demand of advanced copper alloy materials in China's emerging industries and major engineering fields such as electrics and electronics, new generation mobile communications, new energy vehicles, aerospace, and Rail Transit, the Development Status and gap of high strength and high conductivity copper alloy, wear resistant and corrosion resistant copper alloy, ultra high strength elastic copper alloy, advanced copper matrix composite, high precision copper and copper alloy fine wire and ultra thin foil are reviewed. On this basis, the typical market demand of the above-mentioned advanced copper alloys is analyzed, and the medium and long-term development goals and key technologies of China's advanced copper alloys are demonstrated. The study also proposes to promote the overall planning and integrated development of "production, teaching, research and Application Management" , enhance the capability of Equipment Development, technological R & D and market expansion, and strengthen the research and formulation of product standards, suggestions on the industrial development of establishing the training system of the young scientific and technological backbone talents. It is expected to promote the green, high-end and intelligent development of China's advanced copper alloy materials by improving the independent innovation system of copper alloy materials, equipment, technology and industrialization, guided by the key areas of the national economy and the needs of national defense construction.

Keywords: Copper Alloy; High Strength; High Precision; functional application;

1.Introduction

Such policy documents as the outline of the national medium-and long-term plan for the development of science and technology and the guide for the development of the new material industry clearly state that, new-generation information technology, advanced rail transport equipment, aerospace equipment, energy-saving and new energy vehicles are the key areas of high-tech development in China. One of the key basic materials in these fields is high performance copper alloys. High-performance copper alloys have a series of excellent properties, such as high electrical conductivity, high thermal conductivity, high strength, high corrosion resistance, and so on.

The output and consumption of copper products in China rank first in the world. According to the calculation of the total output and import volume including various commonly used copper products, the domestic satisfaction of general copper products has reached 96% . Advanced Copper Alloy materials and components play an important role in national security, major projects and economic construction. However, various high-performance copper alloy materials are heavily dependent on imports, such as new high-strength and high-conductivity Copper Alloy Strip, ultra-fine wire, ultra-thin strip and so on.

The development of advanced copper alloy materials and its new technology of high efficient and short process processing plays an important supporting role in promoting the development of strategic emerging industries and pushing China forward from a material power to a material power. In this paper, the development and application status of copper alloy materials in many fields are reviewed from the point of view of the application of copper alloys in national major projects and emerging industries, and on the basis of analyzing the development trend and typical market demand of advanced copper alloy materials, the medium and long term development goals and suggestions of advanced copper alloy materials are put forward.

2.Application status of copper alloy materials at home and abroad

With the rapid development of high-tech industry, new materials are developing towards ultra-high performance, high purity and high iteration. Advanced Copper and copper alloys, as core conductor materials, are widely used in electronic and information industry, lead frame of Very-large-scale integration, electronic countermeasure, radar, high power microwave tubes, high pulse magnetic field conductor materials, high-speed Rail Transit overhead conductors, high-power frequency and speed regulation asynchronous Traction motor guide bars and end rings, resistance welding electrodes, battery materials, charging post elastic materials for new energy vehicles, continuous casting machine for metallurgical industry, mould, electric vacuum device, switch touch bridge and all kinds of wires, etc. 

(1) High strength and high conductivity copper alloy

High-strength and high-conductivity copper alloy is mainly used in lead frame strip of integrated circuit, rail transit contact wire, high-voltage electrical contact and other components. There are more than 100 kinds of high-strength and high-conductivity copper alloy materials on the international market, which are mainly used in CU-FE-P, Cu-Ni-Si and Cu-Cr-Zr systems. In the field of CU-FE-P and Cu-Ni-Si alloys, a series of grades have been developed abroad, such as C19400(CUFEP) and C70250(CUNISI) of Universal Metalwork Co. , Ltd. , japan's joint-stock company Tamac194(CUFEZNP) , Furukawa Electric joint-stock Company's EFTEC6(CUFEP) , Kobe's joint-stock company's KLF5(CUFESNP) and Klf118(Cunisizn) , and Japan's joint-stock company's NKC114(Cunisizn) . As for the lead frame strip, the most widely used is still the medium strength and high conductivity Cu-Fe-P alloy (such as C19400, KFC, etc.) , which was first developed by Universal Metal Products Co. , Ltd. , the invention has the advantages of low cost, medium strength, high conductivity, high thermal conductivity, good solderability, wettability, processing formability, etc. . Chalco Luoyang Copper Co. , Ltd. , Zhongtong Huazhong Copper Co. , Ltd. , Ningbo Xingye Shengtai Group Co. , Ltd. and Ningbo Bowei Alloy Material Co. , Ltd. have realized the commercial production of C19400 alloy, has a major share of the domestic market. In order to ensure the comprehensive properties of CU-FE-P alloy, the softening temperature of Cu-Fe-P alloy was increased by nearly 50 °C. Ningbo Xingye Shengtai Group Co. , Ltd. , chalco Luoyang Copper Co. , Ltd. , Ningbo bowei Alloy Material Co. , Ltd. and Ningxia Dongfang Tantalum Co. , Ltd. have realized the industrialization of C70250 alloy strip.

Cu-Cr-Zr alloys are ideal materials for high speed rail contact wires and Very-large-scale integration frames. The PHC-120 contact wire developed by joint-stock Company in Japan belongs to this alloy system. In recent years, American, Japanese and German companies have developed heat-resistant Cu-Cr-X alloy lead frame strips, such as KME group's C18160, weyland group's C18080 and Mitsubishi's joint-stock Company's C18141, with tensile strength of 540 ~ 630MPA, the conductivity is 79% ~ 84% IACS (international standard for annealed copper) . The composition optimization and microstructure regulation of Cu-Cr-Zr alloys have been systematically studied in China, and the industrialization of Cu-Cr-Zr Alloy Strip with independent intellectual property rights has been realized by Ningbo bowei Alloy Material Co. , Ltd. 

(2)Wear and corrosion resistant copper alloys

The common wear-resistant and corrosion-resistant copper alloys include tin bronze, aluminum bronze, manganese white copper and complex brass. The tensile strength of the castings is 400 ~ 500 MPA, the hardness is 100 ~ 200 HBS (Brinell hardness) , the elongation is 6% ~ 10% , the tensile strength of the extruded materials is 600 MPA, and the hardness is over 200 HBS. The main overseas producers are Japan's Joint-stock Company, Sumitomo Heavy Industries joint-stock Company, the domestic Aluminum Luoyang Copper Co. , Ltd. , Luoyang Shuangruidate Copper Co. , Ltd. . The main corrosion-resistant copper alloys of Cuni series for marine engineering are B10(Cu-10Ni-1Fe-1Mn) and B30(Cu-30Ni-1Fe-1Mn) alloys. The maximum diameter of seamless corrosion-resistant cupronickel drainage pipe produced in Germany and Korea is more than 520 mm, and the wall thickness is 0.7 mm. In China, the development of large-diameter corrosion-resistant white copper pipe is relatively late, the corrosion resistance is unstable, the service life is low, and some high-end corrosion-resistant Cu-Ni-Fe alloy pipe products depend on imports. The tensile strength of CuNiSn alloy is up to 1000MPA, and the corrosion resistance of CuNiSn alloy is better than beryllium copper and aluminum bronze in seawater, acid, oil and gas and high load. At present, all the high-end high-strength CuNiSn alloys used in China are imported, among which the products of Materion Group of America, Joint-stock Company of Japan and Claire Special Metals (France) Co. . The relevant agencies in China are jointly working on the continuous casting technology and complete sets of equipment, the deformation heat treatment system, the deformation structure and the internal stress distribution characteristics of CuNiSn alloy under the special casting environment, as well as its control technology, the base of localization of the alloy was established.

3. Ultra high strength elastic copper alloy

Ultra-high strength elastic copper alloys generally refer to copper alloys with a strength of more than 1000 MPA and an elastic modulus of more than 125 GPA. The elastic copper alloys for high reliability connectors are mainly beryllium copper alloys. The production and application of beryllium copper alloy in developed countries have reached a very high level, and the related equipment and production technology are still being innovated In particular, the United States (represented by the Materion Group) and Japan (represented by the joint-stock company) are large-scale production, production technology and equipment level in the world's leading position. Beryllium copper alloy contains toxic material beryllium, the stress relaxation rate increases sharply at higher than 150 °C, which easily leads to the change of contact pressure of elastic components in working state, and leads to the failure of connectors. The development of a new type of copper alloy with high strength, high stress relaxation resistance, excellent formability and high reliability has become a hot spot in the field of elastic materials. Cu-Ni-Mn, Cu-ti and Cu-Ni-Sn alloys are age-hardening alloys. After deformation and heat treatment, the strength and elastic properties comparable to those of beryllium-copper alloys, as well as better corrosion resistance and stress relaxation resistance, can be obtained. These alloys have been developed by French, American, Japanese and other enterprises, and have partially replaced beryllium copper alloy industrial application. Some domestic copper processing enterprises are trying to manufacture Cu-Ti alloy products, but the key processing technology of large-scale production is still to be fully broken through, resulting in the existing Cu-Ti alloy materials can not be self-sufficient.

4. Advanced Copper Matrix composites

Advanced Copper Matrix composites are the key materials for lh-lox rocket engine linings, ehv switches, electrodes and other components. In the aspect of copper matrix composites with high conductivity, carbon nanotubes and graphene are introduced to develop carbon nanotubes/graphene reinforced copper matrix composites with high strength and high conductivity. The tensile strength is more than 500MPA, and the conductivity is 115% iacs. In the field of anti-electromagnetic shielding copper matrix composites, Japanese enterprises have developed a series of CFA alloys, such as CFA95, which has a shielding effect of 50ー80 db on magnetic field and more than 80 DB on electric field, and its conductivity is 60% ー70% iacs. Shaanxi Sirui New Materials Co. , Ltd. , Ningbo Jintian Copper (Group) Co. , Ltd. and other domestic enterprises are also building CuFe alloy manufacturing base. In the field of high strength, high conductivity and high temperature annealing softening copper matrix composites, SCM Metal Products Co. , Ltd. has developed various grades of Cu-Al2O3 dispersion strengthened copper alloys (such as C15710, C15720, C15760, etc. . The heat resistance of Cu-Al2O3 dispersion strengthened copper alloy is up to 900 °C, which is mainly used for electrode of electric welding, medical image device and electric vacuum device. Domestic institutions such as chalco Luoyang Copper Co. , Ltd. and Youyan Engineering and Technology Research Institute Co. , Ltd. have also launched independently developed dispersion strengthened copper alloy products, mainly used for welding electrode of automobile coating steel plate, battery nickel sheet, aluminum and aluminum alloy, etc. . In addition, some special functional copper matrix composites are also used, such as anti-corrosion CUCR contact materials, high thermal conductivity and low expansion CuW electronic packaging materials, ultra-high strength and high conductivity Cu-Nb composite materials (room temperature tensile strength can be greater than 1400 MPA, conductivity higher than 70% IACS) and so on.

5. High precision fine wire and ultra thin foil for copper and copper alloys

With the increasing popularity of micro-electronics, ultra-micro electronics, new generation mobile communication, intelligent robot and other products, the demand for ultra-fine and high-performance ultra-thin copper foil is increasing. In fine wire, the supply and demand of fine wire of different specifications in domestic market are very different: the supply of copper wire with diameter over 0.04 mm is more than the demand, the price is low and the competition is fierce; The domestic demand for ultra-fine (diameter 0.015 ~ 0.04 mm) copper conductors is larger than the production capacity, and more than 60% of ultra-fine copper conductors with diameter less than 0.015 mm rely on imports. In recent years, some domestic manufacturers have started the research and development of fine copper filament, but limited by the equipment and technology, product yield rate is low, uneven performance, still can not meet the needs of the micro-electronics industry. In the field of ultra-thin foil, many domestic high-grade Copper Clad laminates and printed circuit board rolled copper foil with high flexibility and high mechanical strength are required, most of the supply is dominated by foreign companies such as joint-stock Company, Joint-stock Company, USGS and Joint-stock Company. At present, it has been realized that the tensile strength of the foil is ≥500 MPA when the thickness of the foil is ≤33 m, the tensile strength is ≥150 MPA, the elongation is ≥10% and the bending times are ≥7.6108 under the heat treatment conditions of 135 °C and 30 min. Some domestic enterprises, such as China nonferrous metals corporation and Lingbao City Huaxin Copper Foil Co. , Ltd. , can produce high quality rolled copper foil of partial specifications on a large scale. In the aspect of surface treatment of rolled copper foil, the domestic enterprises only master the ashing treatment technology, but the blackening treatment technology is still to be developed.

3.Application demand analysis of advanced copper alloy materials in China

(1)High strength and high conductivity copper alloy

(2) Wear and corrosion resistant copper alloys

(3)Ultra high strength elastic copper alloy

(4)Advanced Copper Matrix composites

(5)High Quality ultra-fine conductive copper alloy wire

(6)High strength and high conductivity die cast copper alloy

(7)Ultra thin calendered copper foil for Electronics

(8)Environment-friendly free-cutting copper alloy materials

4.Development trend and problems of advanced copper alloy materials in China.

(1) Technology trends

In recent years, great progress has been made in the overall level of high-performance copper alloys and their preparation technologies in China, and the variety of high-performance copper alloys with independent intellectual property rights has been increasing, the level of copper alloy material processing and installation is close to the international advanced level. The developing trend of research and development and industrialization of advanced copper alloy materials is as follows. (1) from single performance requirements to multi-functional requirements. For example, copper-based materials with high thermal conductivity and electromagnetic shielding properties should meet the needs of conductor materials in high-precision fields such as pulsed high-intensity magnetic field systems and particle-accelerated electromagnetic emitters, in addition to the need for high electrical conductivity, higher strength, wear resistance and fatigue resistance are required; Very-large-scale Integration Copper Alloys require high strength and high conductivity, heat resistance, bending resistance, and easy etching. (2) copper processing materials are developing towards fine, thin, long and high precision. The demand for ultra-fine wire, ultra-thin Strip, thin-wall Tube, ultra-long Tube, ultra-long strip, threaded tube, special-shaped tube, special-shaped Bar, special-shaped strip and other products continues to increase, such as lead frame embodies the multi-foot, high-density, ultra-thin, micro-development trend. (3) high purification of copper. The content of copper in industrial copper was increased from 99.9% to 99.95% , and then to 99.99% or even higher. Ultra-pure copper containing 99.9999% copper will minimize the influence of impurities on the conductivity and thermal conductivity. (4) composite materials. The potential of the single material strengthening method is limited, so it becomes a research hotspot to improve the comprehensive properties of copper by using the composite method. For example, adding second phase particles, whisker or fiber to copper alloy to strengthen copper matrix, and developing new multifunctional copper matrix composites, it is of great value to the design theory of high performance copper alloy and the practical application in the field of high and new technology.

(1)Problems faced

Although China is the world's largest producer of copper alloy materials, it is still not a strong country of copper alloy materials. High-performance copper alloys, which are urgently needed in many high-tech fields such as aerospace, electronic information, ocean engineering and high-end equipment, are still more dependent on imports The copper alloy material production enterprise is numerous, the Concentration ratio is low, the product competitive power is weak, the profession profit is meager, can not support the high-tech industry development. The main problems 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 comprehensive properties of some high performance copper alloys are generally lower than those of similar imported products, such as Cu-Ni-Si, Cu-Cr-Zr lead frame and strip developed by ourselves. (2) the stable production capacity of large-size and high-quality copper alloy products needs to be improved urgently, for example, the performance stability, surface quality and composite products of high-precision elastic copper alloy strips still need to be broken through. (3) the processing technology of high performance copper alloy is not mature, and the quality and performance of the product need to be improved. (4) the lack of independent manufacturing technology for some high-end production equipment limits the development of new products, such as the dependence of most high-precision foil production equipment on imports. (5) some high-end copper alloy materials lack of independent Intellectual Property Rights and Public R & D Platform, and the database construction of material properties, production technology, standards and specifications is lagging behind. (6) the large-scale homogenization preparation technology of oxygen-free copper with ultra-high purity and ultra-low oxygen content needs to be further improved, and the preparation technology of high-precision, large-diameter and Long-life Corrosion-resistant cupronickel needs to be further developed.

Countermeasures and suggestions

 1. To promote the overall planning and integrated development of the "management of production, study, research and application" under the guidance and support of policies and in accordance with the layout of the country's scientific and technological fields, the cooperative mechanism of "production, teaching, research and application of tubes" will be implemented jointly by copper alloy preparation and processing enterprises, scientific research institutes and application units. Focus on the advantages of "production, study, research and application" , break through the key preparation and processing technology of high-end copper alloy basic raw material products, which restrict the development of major projects and emerging industries in China, and solve the "neck jam" problem, promoting the construction of advanced copper alloy manufacturing power. To establish and improve four platforms, namely, "Technological R & D and Innovation" , "personnel training and introduction" , "information and Exchange" , "policy support and guarantee" , in order to provide reliable and continuous technical and personnel support for the development of advanced copper alloy industrial clusters, to provide a model for the establishment of National Industrial Development Zones. 2. To enhance the capability of Equipment Development, Technology R & D and market expansion, to learn from the international advanced experience and development process, to rely on independent scientific and technological innovation, to establish industry big data to drive the whole manufacturing process of copper and copper alloy materials. With the development of industry-related equipment as the core, it covers advanced continuous casting and continuous rolling (continuous extrusion) units, continuous drawing and continuous plating units, continuous drawing and continuous plating units, ultra-fine drawing and wire annealing plating/coating units, etc. , reduce Energy consumption and raw material loss rate, improve product performance and quality stability, improve market competitiveness and share. 3. Strengthen the research and formulation of product standards for high-end manufacturing requirements for advanced copper alloy materials, and establish and improve the standard system for advanced copper alloy products and production technology. To establish national or industrial technical standards for new products such as ultra-fine copper wires (including tinned wires and enamelled wires) and special copper-based composites, improve standards and methods for recycling copper resources, and standardize the order from the source, to ensure the healthy and sustainable development of the industry. 4. The establishment of an advanced copper alloy training system for young scientific and technological cadres will enrich academic/technical discussions, strengthen exchanges between technical experts and young scientific and technological cadres, coordinate the application between the military and the people, and promote cooperation between enterprises across the ownership system. To promote the expert team to serve the enterprise's "wisdom" model, and make suggestions for the enterprise's products, to overcome specific technical problems as the goal to develop expert service production "precision poverty alleviation. Construction and promotion of Advanced Copper Alloy talents combined with "old, middle and young". 

Source: China Engineering Science, 2020 volume 22, No. 5 by: Jiang Yexin, Lou Huafen, Xie Haofeng, Li Tingju, Song Kexing, Liu Xuefeng, Yun Xinbing, Wang Hang, Xiao Zhu, Li Zhou