Aluminum rod manufacturing technology
Apr 20, 2021
Our country has at least 400 to 500 aluminum wire drawing machines, most of which are domestically made centralized wire drawing machines. Since they were used in the 1950s, there has been almost no essential improvement, which is comparable to the high speed of modern foreign drawing aluminum wires. Compared with the wire drawing machine, the gap is obvious. There are few high speed aluminum wire drawing machines imported from abroad in China, which play a major role in production. The domestic high-speed aluminum wire drawing machine is under active development. In small factories of township enterprises, there are still a certain number of low-efficiency single-die wire drawing machines, which should be replaced, modified or eliminated as soon as possible.
⑴ Aluminum rod manufacturing technology As mentioned above, there are three methods for manufacturing aluminum rods. The method of aluminum rod production in shaft furnace and continuous casting and rolling is the most advanced and most commonly used. However, since the birth of this method in the 1960s, There are few essential improvements, but as the industrial development has higher requirements for the quality of aluminum rods, more improvements are needed, especially when used in the manufacture of high-strength aluminum alloys.
From the early 1990s to the present, the continuous casting and rolling mills for manufacturing aluminum rods have been improved successively. The main improvements are:
① Use tilting holding furnace to replace the original open hearth furnace, which can ensure that the aluminum water in the furnace can be poured clean every time the furnace is opened, so that the chemical composition of each furnace can obtain a satisfactory result, which is more important for the manufacture of aluminum alloy ；
② The continuous casting machine is changed from two-wheel type to four-wheel type, so that the ingot will not be twisted when it leaves the casting wheel, and it will be straight and not skewed when entering the rolling mill. The cooling system of the casting wheel can be cooled on all four sides, the flow of the nozzle can be adjusted, and the cooling water surface is fan-shaped, so that the ingot cooling is very uniform;
③ Replace the previous unified Y-shaped structure with a new type of roller arrangement; the first two lanes are of two-roller vertical roller structure, and each subsequent lane still has a Y-shaped structure, so as to ensure that there is a large and sufficient pressure during the first two lanes. Therefore, the cross section of the ingot can be appropriately enlarged, and the aluminum rod can be fully deformed and has better performance;
④ Since the cross section of the ingot is appropriately enlarged, and it is possible to roll high-strength aluminum alloy rods, which have higher strength and greater resistance to deformation, increase the motor power of the main machine of the rolling mill;
⑤ In the manufacture of aluminum rods, the molten aluminum needs to be refined and degassed, and the harmful hydrogen in the aluminum is removed. Generally, flux refining is used. This degassing method is not thorough enough. Now, a continuous refining and degassing device is added. After that, the molten aluminum continuously passes through the refining device, and a mixed gas of chlorine and nitrogen is introduced to remove hydrogen and improve the quality of the aluminum rod.
Although the aluminum rod production is improved through the above-mentioned measures, there are still some problems on the equipment. The most obvious is that the fully automatic double-reel winding is not yet possible, which still brings trouble to the next process. In addition to the process equipment for manufacturing aluminum poles, it is also important to obtain electrical aluminum poles with excellent performance, and this technology should be combined with China's national conditions.
⑵ Optimized comprehensive treatment of rare earth to manufacture electrical aluminum. my country needs to use hundreds of thousands of tons of aluminum as wire and cable products every year. However, due to the high silicon content in my country’s aluminum ore, there is a lack of sufficient electrical aluminum ingots. Since the 1980s, When researching electrical aluminum conductors, Shanghai Cable Research Institute uses my country's rich rare earth resources to process ordinary aluminum ingots to reach electrical level. This is the so-called rare earth optimized comprehensive processing technology to manufacture electrical aluminum.
The optimized comprehensive treatment technology of rare earths uses aluminum continuous casting and rolling mills under the production conditions of the cable factory to produce electrical aluminum rods, and then draws, strands, and produces electrical aluminum wires with electromechanical properties that meet international standards. Overhead wire stranded by wire. The core technology of rare earth optimization comprehensive treatment method, including rare earth optimization, boronization treatment and iron control treatment. Rare earth optimization is to reduce the harmful effects of silicon impurity on conductivity. Boronization is mainly aimed at reducing the harmful effects of titanium, vanadium, manganese, and chromium impurities on conductivity. Iron control is to reduce the conductivity and increase aluminum under the conditions of not affecting corrosion resistance. The strength of the base. These three methods can be used individually or in combination according to different material sources, and they are used to achieve the result of manufacturing electrical aluminum conductors.
Since the use of rare earth optimization and comprehensive treatment to manufacture electrical aluminum, a misunderstanding has appeared in the society, and through certain occasions and methods, it is stipulated that the wires for 500kV lines or even 200kV lines should not use "rare earth aluminum wires". This misunderstanding is harmful. Yes, it blurs many scientific concepts and should be corrected. Aluminum conductors manufactured through the comprehensive treatment of rare earths are advertised as "rare earth aluminum wires". In fact, the addition of rare earths is only a means to make ordinary aluminum ingots capable of producing electrical grade aluminum conductors through comprehensive treatment. Therefore, in the misleading public opinion, the "rare earth aluminum wire" can increase the conductivity, but it only makes the aluminum wire made of ordinary aluminum ingots reach the electrical level, that is, the conductivity ≥ 61% IACS, or the resistivity ≤ 0.028264Ω· mm2/m, the same as the standard of electrical aluminum, has not been improved. Public opinion believes that "rare earth aluminum wire" can increase the strength. In fact, rare earths are added to make ordinary aluminum conductors reach the conductivity of electrical aluminum conductors. Under such rare earth content, the strength of rare earth aluminum wires is no better than that of ordinary aluminum. The wire and the electrical aluminum wire are high, but it only meets the strength requirements for the electrical aluminum wire. The good corrosion resistance of "rare earth aluminum wire" is also an unclear concept. The object of comparison should be electrical aluminum wire instead of ordinary aluminum wire. Secondly, it depends on different environments. The first corrosion in overhead wires It is not an aluminum wire, but a steel core. Therefore, light, medium, and heavy-duty corrosion-resistant steel-cored aluminum stranded wires appear, which are used in different occasions.
Using non-electrical grade aluminum ingots, through the optimization and comprehensive treatment of rare earths, electric aluminum wires with a conductivity of 61% IACS and above can be produced by using electrical aluminum ingots; flexible application in production can improve the process performance of metal processing , Improve the yield; in the case that ordinary aluminum ingots are difficult to produce smoothly due to insufficient iron-to-silicon ratio or inversion, the application of olefinic soil optimization can solve the problem smoothly; the aluminum-rare-earth master alloy can be made of aluminum-rare-earth master alloy by making full use of the scrap aluminum from the cable factory For production.
The optimized comprehensive treatment method of rare earth enables the aluminum ingots to obtain various properties of electrical grade aluminum conductors after treatment. This method is unique in my country. From the 1980s to the 1990s, most factories producing aluminum conductors in my country have mastered it. With this method, the performance of hundreds of thousands of tons in our country has been improved to a new level.
⑶ Aluminum alloy wire and its manufacturing technology. In the world, aluminum-magnesium-silicon type high-strength aluminum alloy wire has been used for more than 70 years. Due to its advantages and continuous improvement of its production process, it has more advantages. Actual use value. In Europe, represented by France, it is widely used on transmission lines, accounting for most of the total line length; Japan uses more than 50% of aluminum alloy transmission lines; the United States and Canada also have a large proportion; even in developing countries in Southeast Asia , India, Indonesia, the Philippines, etc. also use aluminum alloy for wire transmission lines.
If you compare the all-aluminum alloy stranded wire with the steel-cored aluminum stranded wire, under the same unit weight, the aluminum alloy conductor has the advantages of low DC resistance, large current carrying capacity, large tensile force, and large tensile unit weight ratio; it has the same advantages Compared with the current-carrying capacity, the aluminum alloy wire has the advantages of lighter weight, higher tensile force, and greater tensile force per weight ratio. In addition, the aluminum alloy wire is a single-material wire, which is easy to install and construct. It has the advantages of increasing the gear span, reducing the number of poles, or reducing the height of poles in line construction. In short, it can reduce the project cost, so it is welcomed by the power sector.
Since the mid-1960s, our country has begun to study aluminum alloy conductors on a large scale and has accumulated a lot of experience from the research process formula, process, special equipment, test technology, erection and operation, etc., which lasted more than 30 years. And formed a number of unique technologies in our country. However, high-strength aluminum alloy wires have not been widely used in China, and are only used in certain occasions. The main reason is that the alloy performance is not stable enough and the price is high. So the reason for this is that the aluminum alloy production factory built after the mid-1960s was destroyed in a natural disaster in the early 1970s, and when another aluminum alloy factory was rebuilt in the mid-1970s, it encountered that again. In the 1980s, it was impossible to have the world’s advanced technology and equipment for the production of aluminum alloys, and this situation remained until the mid-1990s.
In the newly constructed aluminum alloy factory in the mid-1990s, the production equipment adopted contemporary new equipment and introduced my country’s unique advanced production technology. The products produced not only meet the requirements of the standard, but also have a large margin, which is deeply appreciated. User praise. The main technological advances are:
① In addition to the tilting holding furnace and the continuous degassing refining device outside the furnace, the aluminum continuous casting and rolling also adds a continuous quenching device, so that the process of producing aluminum rods can be continuously completed at one time;
② Wire drawing machine, so that the aluminum alloy wire will not be twisted during drawing. The heat of the high-speed cable will also be utilized;
③ Continuous aging furnace, the furnace has an extremely high-precision furnace temperature control system, and uses the waste heat of the wire drawing machine to fully utilize the heat;
④ It adopts rare earth treatment, which has the characteristics of China's original creation.
On the basis of the above, at the end of the 1990s, improvements were made on the original basis and more modernized. Its technological advances include:
① A specially manufactured aluminum alloy continuous casting and rolling mill is used. On the basis of summarizing the previous advantages, a rapid heating device is added to keep the aluminum ingot at a constant temperature when it enters the rolling mill. The temperature measurement and display devices before and after the rolling mill are added to ensure that the aluminum alloy ingot is in the best state during rolling. Good take-up device enables the aluminum alloy rod to be wound and adhered, creating conditions for the next process;
② The wire drawing machine and the aging furnace adopt automatic rail connection;
③ Continuous aging furnace, using manipulators for loading and unloading, the furnace temperature is automatically displayed and can be adjusted at will.
After using these measures, the quality of the aluminum alloy wire will be better and more stable. When mass production, the price drops significantly, these two points just overcome the weakness of the restricted use of aluminum alloy wires in China.
In addition to aluminum-magnesium-silicon type high-strength aluminum alloys, heat-resistant aluminum alloys have also been developed. There are two types of heat-resistant aluminum alloys, the conductivity of which is 58% IACS and 60% IACS, the tensile strength is 160N/mm2, and the long-term working temperature is 150°C. Heat-resistant aluminum alloy wires are used in power stations and substations; especially in urban reconstruction, they can be used as capacity-increasing wires to facilitate the transformation of old lines. Another development direction of aluminum alloy is high-strength heat-resistant aluminum alloy, high-strength and high-conductivity aluminum alloy. In short, aluminum alloy varieties have formed a series in our country, and the main problem is how to further recommend and apply them in engineering.
my country has a specialized factory for the production of high-strength aluminum alloys. Since the mid-1990s, the quality of the aluminum alloys produced is in full compliance with the items specified in the IEC, ASTM and GB standards, and the performance is good. Shanghai is currently planning to build another factory specializing in the production of aluminum alloy wires, which will provide high-quality aluminum alloy wires for the power industry, which is expected to be available in 2000.
④ Aluminum profiles The aluminum profiles in the wire and cable industry mainly include: fan-shaped cross-section profiles as cable cores, flat wires for transformers, and arch, Z-shaped, and head-shaped profiles for transmission lines. They need to be several kilometers in length without joints, and the cable cores should also be flexible wires. These products are usually made of aluminum rods by rolling and drawing. The cords need to be annealed, and the surfaces of these products are easily scratched.
