ABSTRACT: This paper introduces the application of continuous extrusion technology in the production of oxygen-free Copper Strip. The oxygen-free Copper Strip produced by this technology not only has excellent mechanical properties (Cu + Ag ≥99.99% , oxygen content ≤5ppm, conductivity ≥101% IACS) ; Moreover the production flow is short, the production efficiency is high, the finished product rate is high, the delivery time is short. Keywords: continuous extrusion; oxygen-free Copper Strip classification: TG372 DOCUMENT ID: a Article Id: 1671-6795(2011)04-0029-02

Oxygen-free copper tape is a high-tech, high-purity, high conductivity, low oxygen content and other special properties of materials, widely used in power, electrical, electronics, communications and other industries, for the manufacture of vacuum tubes, computers, miniature radiators, Flexible electronics, connectors, coaxial RF cables, pv soldered copper substrates, dry, transformer, winding and other high end product components [1.2]. With the development of the global economy in the direction of energy saving and environmental protection, the demand for oxygen-free copper strip is increasing, and its excellent product performance puts forward higher requirements for the processing difficulty of oxygen-free copper strip, in particular, the large length, high precision, high surface quality of the Strip processing, but also the need for advanced processing technology and equipment to ensure. The working principle of the continuous extrusion technology is shown in Fig. 1. The die cavity is located on the side of the extrusion wheel, and the billet is driven into the extrusion cavity by the rotating extrusion wheel, after a certain value is reached, the product is extruded from the die hole. The size and shape of the product depends on the mold, just need to replace the mold can produce different specifications of the product.

1. Manufacturing process

The technological process of producing oxygen-free copper strip by continuous extrusion is as follows: Continuous Casting oxygen-free Copper Rod by up-drawing and continuous casting

1.1 continuous casting oxygen-free copper rod with top lead

Using high purity electrolytic copper as raw material, the electrolytic copper was preheated, dried and melted. The crystallizer water pressure was 2ー4 MPA, the crystallizer water temperature was 35 °c ー50 °C, and the copper liquid temperature was 1150 °C ± 10 °C. The high quality of oxygen-free Copper Rod is ensured by on-line refining technology. The CU + Ag ≥99.99% , the oxygen content ≤5ppm and the electrical conductivity ≥101% IACS are obtained. The diameter of the oxygen-free copper rod is 20 ~ 30 mm.

1.2 continuous extrusion of copper strip stock

TheФ 20 ~ Ф30mm oxygen-free copper rod is straightened and fed between the compaction wheel and the extrusion wheel. The copper rod in the groove of the extrusion wheel is fed into the extrusion cavity continuously under the action of friction. The blank moves in a circle in front of the cavity block, after the friction shear deformation zone, upsetting deformation zone, adhesion zone, right angle bending extrusion zone and other areas, finally into the cavity through the die extrusion copper strip billet. After extruding the die, the copper strip is cooled by the vacuum anti-oxidation tube and the water tank, and dried to 20 °C ~ 30 °C. Continuous extrusion machine speed is 3 ~ 10r/min, shoe block pressing pressure is 30 ~ 40MPA, copper strip billet extrusion speed is 3 ~ 15m/min, copper strip billet size is 320 ~ 15mm.

2. Technological advantage

 2.1 traditional manufacturing process for oxygen-free copper strips

The traditional process for producing oxygen-free copper strip can be divided into two types: refining and horizontal continuous casting, as asThe two methods are simply called horizontal continuous casting method for cold rolling and semi-continuous casting method for hot rolling. The method of horizontal continuous casting —— Cold Rolling has been paid more attention because of its low investment, short process flow and high product rate, and because of the limitation of smelting process, its oxygen content is unstable, it is difficult to meet the requirements of high-purity and high-conductivity oxygen-free Copper Strip. The semi-continuous casting-hot-rolling process is used to make the metal plastic deformation under the condition of complete recrystallization. In this process, because of the large processing rate and full recrystallization, the defects such as shrinkage cavity, porosity and air bubble in as-cast microstructure can be compacted or welded, the grains can be refined, and the microstructure and properties can be improved remarkably. However, the hot rolling needs heating, the process is complicated, the capital investment is big, the energy consumption is high, the production cost is high.

2.2 advantage of continuous extrusion technology in producing oxygen-free Copper Strip

In view of the shortage of the traditional production technology of oxygen-free Copper Strip, the continuous extrusion method has the following advantages: 1 although the billet is not heated during continuous extrusion, the deformation temperature reaches above 600 °C under the action of the friction force in the extrusion groove, under the action of high temperature and high pressure, the extruded products have fine grain, compact structure, superior comprehensive performance and high quality. 2 continuous extrusion technology changes the useless friction force in pressure processing into the driving force and heating source of metal deformation, and the billet does not need to be heated;

3 The whole process of continuous extrusion is carried out under the sealed vacuum. After the Strip is extruded out of the die, it is cooled directly into the cooling groove by the anti-oxidation pipe. The surface is smooth, no oxide skin is produced and no milling surface is needed. The yield of the product can reach about 75% The oxygen-free Copper Strip produced by continuous extrusion technology uses the oxygen-free copper rod as raw material, and the purity and oxygen content of the oxygen-free Copper Rod are easier to control, it can meet the requirement of Tu0 oxygen-free Copper Band (Cu + Ag ≥99.99% , oxygen content ≤5ppm, conductivity ≥101% IACS) . The results of oxygen-free Copper Strip analysis are shown in Table 1, and the metallographic structure is shown in figure 2

The delivery time is short, the production cycle is about 7 days. The continuous extrusion technology for producing oxygen-free Copper Strip shortens the whole process flow, not only reduces the operating cost of the whole copper strip production line, but also contributes greatly to the realization of energy saving and emission reduction and green manufacturing.

3. Application

The production of oxygen-free copper strip by continuous extrusion not only has excellent mechanical properties by hot rolling, but also has the advantages of high purity, high conductivity and low oxygen content (Cu + Ag ≥99.99% , oxygen content ≤5ppm, conductivity ≥101% IACS) , can Be widely used in electric power, electrical appliances, electronics, communications and other industries production of high-end product components, such as photovoltaic copper tape, coaxial radio frequency cable, transformer copper tape, electronic stamping parts, precious metal composite tape, computer micro radiator, Flexible electronics, etc. .

4. Conclusion

The oxygen-free Copper Strip produced by continuous extrusion technology not only has compact structure, fine grain, good mechanical properties and high quality, but also has the advantages of high purity, high conductivity and low oxygen content (Cu + Ag ≥99.99% , oxygen content ≤5ppm, conductivity ≥101% IACS) . The technology has the advantages of short production flow, high efficiency, high finished product rate and short delivery time. In the power, electronics, electrical appliances, communications and other industries widely used to produce photovoltaic copper tape, coaxial video cable, transformer copper tape, electronic stamping parts, precious metal composite tape, computer micro-radiator, Flexible electronics and other high-end products.

 Source: Chinanews.com, by Luo Yuefeng