Abstract: This paper briefly introduces the development status and trends of aluminum and aluminum alloy tubes, rods, wires, and wire rods, and focuses on the development of aluminum and aluminum alloy extrusion, cold-rolling and drawing of tubes, tubes, rods, and models. The development characteristics, level, product variety, process technology, tool and die technology and equipment status of heat treatment and wire straightening and wire straightening and other aspects. In recent years, the production technology and equipment of aluminum alloy tubes, rods, wires and wires at home and abroad have achieved considerable development and reached a very high level. Aluminum extrusion technology status and development direction
1.1 Status of Aluminum Extrusion Technology
1.1.1 Development of Process Equipment to Large-scale, Modernization, Precision and Production Line Automation
Extrusion equipment mainly refers to the extruder and its associated equipment, which is an important indicator reflecting the level of extrusion technology. According to rough statistics, there are more than 6,000 extrusion presses of different types, structures, uses, and pressures in various countries in the world, of which more than 600 are from the United States, 400 are from Japan, 200 are from Germany, 400 are from Russia, and 3,000 are from China. Most of them are small and medium sized extruders between 6MN and 25MN. With the development of the modern transportation industry such as large transport aircrafts, bombers, missiles, warships and other military industries, underground railways, and high-speed trains, a large number of structural components such as integral panels are needed, so the extrusion machine has grown toward large scale. In the 1950s, the United States Air Force decided to use government funds to build a series of heavy-duty extruders and forging presses. The United States Air Force's "heavy press plan" originally planned to manufacture 17 large-scale presses and then reduced it to nine, of which 350 MN vertical forging-extruding machines and 120 MN and 80 MN aluminum alloy horizontal extruders each had two units.
After decades of development, the world has officially put into operation about 20 sets of large-scale extrusion presses with a capacity of 10,000 tons or more. The countries in possession are the United States, Russia, China, Japan, and Western Europe. The larger one is the 200MN extrusion machine of the former Soviet Union’s Kuibyshev aluminum processing plant. In the United States, in 2004, a 125MN hydraulic press was transformed into the world’s largest 150MN hydraulic press. Japan was in the late 1960s. A 95 MN self-suppressing press was built. The German VAW Bonn plant put into operation a 100 MN double-acting hydraulic press in 1999. Italy completed and commissioned a 130 MN copper and aluminum hydraulic press in 2000. . According to reports, several industrially developed countries abroad are developing more pressure and more innovative forms of extrusion presses, such as 350 MN horizontal extrusion presses and 450 MN to 600 MN grades of large diameter extruded pipe forgings. Pressure combined hydraulic press and so on. In terms of extruder body, in recent years, foreign countries have developed steel composite frames and prestressed "T" head-board column structure racks and prestressed concrete racks. A large number of flat extrusion cylinders, fixed extrusion gaskets, and movable molds have been used extensively. Shelf and built-in stand-alone perforation system. In the form of transmission, self-propelled oil drive system has been developed. Even the 100 MN ~ 150 MN extruder has adopted the oil pump direct drive. Modern extruders and their auxiliary systems use PLC (program logic control) systems and CADEX control systems to achieve speed control, isothermal-isokinetic extrusion, automatic tool loading and unloading, and even full machine automation. control. Pre-machine equipment for extruders (such as long billet auto-control furnaces, billet blading equipment, billet transport equipment, etc.) and after-machine equipment (such as traction equipment, precision water, fog, air quenching equipment, front beam saws, activity work Benches, cooling beds and transverse conveyors, tension levelers, finished saws, artificial aging furnaces, etc. have been automated and continuously operated. Extrusion equipment is moving toward assembly, integration, and standardization [1-6].
In order to further adapt to the light weight and high speed of modern military equipment and the modern transportation industry, aluminum profiles are being developed toward large-scale, integrated, and thin-walled. As a result, countries around the world are raising the heat of a heavy-duty extruder, and it is predicted that the 21st century will be the century of large-scale extruders.
1.1.2 Breakthrough progress in large-scale high-quality circular, flat extrusion barrels and special mold technology
From the point of view of design calculation, structure selection, loading and unloading methods, mold making techniques, development of new materials, and improvement of mold life, there is a great development in extrusion tooling technology. Developed tongue molds, flat-flow split molds, yoke molds, anterior chamber molds, diversion molds, removable molds, wide spread molds, and water-cooled molds. At the same time, various types of movable molds and tools have emerged for automatic loading and unloading. The mechanism greatly simplifies the loading and unloading operations of the tool and mold and saves the auxiliary time. In order to produce flat-width, thin-walled, large-section aluminum alloy profiles, high-compression round extrusion cylinders and high-quality flat extrusion cylinders are required. Due to their short service life, the design and manufacture of large, high-pressure flat extrusion cylinders Has become a worldwide technical problem. In recent years, as a result of advances in computers, finite element calculations, tooling materials, and heat treatments, breakthroughs have been made in the design and manufacture of large flat extrusion cylinders. Russia, the United States, Germany, Japan and other countries have developed large-sized flat extrusion cylinders with specifications of 850mm×330mm, 1100mm×300mm, etc., with a specific pressure of more than 600MPa, and the service life is said to be about 10,000 times; China has successfully developed 670mm × 270mm × 1600mm large-scale high-quality flat extrusion tube. Large-scale extrusion tools have also made great progress in the automation of loading and unloading, and have created conditions for the automation of the whole machine. In terms of tool and die materials, high-alloyed chromium-nickel die steels, such as the 2779 (Germany), H11, H13 (United States), SKD61 (Japan), AXMBΦ (former Soviet Union) and other steel types, and new heat treatment methods, such as The application of vacuum quenching, ion nitriding treatment and surface hardening treatment has greatly advanced the quality of tool and die materials. EDM and WEDM (fast walking and slow walking) technologies are used for mold making, which not only improves the precision and hardness of the die hole, but also reduces the surface roughness of the working belt, and greatly improves the efficiency of the production of the mold. It has created the conditions for the automation of model making. Electronic computers are used in the design and manufacture of extrusion tooling (CAD/CAM technology), which opens up a new path for the automation of the design and manufacturing of tooling and moulds, as well as the improvement of the quality and life of tooling.
1.1.3 The extrusion process continues to improve and improve
In recent years, in addition to improving and perfecting forward and reverse extrusion methods and processes, many new processes and new methods have been developed to strengthen the extrusion process, and practical applications have been obtained. Like tongue die extrusion, plane die assembly extrusion, variable section extrusion, water cooled die extrusion, flat extrusion, wide extrusion extrusion, precision gas, water (mist) cold in-line quench extrusion, semi-solid extrusion, High-tech extrusion, cold extrusion, high-efficiency reverse extrusion, isothermal extrusion, special tension-roll straightening, deformation heat treatment and other new technologies and new processes, to expand the variety of aluminum profiles, increase extrusion speed and overall production efficiency, It is of positive significance to improve product quality, explore the potential of aluminum profiles, reduce extrusion forces, save energy, and reduce costs.
1.1.4 The product structure of aluminum extrusions has been greatly improved
Since the 1960s, the average growth rate of aluminum alloy extrusion materials has reached 9.5% per year. This not only exceeds the growth rate of other aluminum alloy processing materials (eg, twice that of rolled steel), but also greatly exceeds that of steel materials. Growth. According to incomplete statistics, the production capacity of extruded aluminum alloys in the world has reached about 20 million t/a, and the annual output in 2006 has reached 12 million tons. As the use of civilian aluminum materials increased greatly, and the proportion of military extrusion materials accounting for the total amount of aluminum extrusion materials has dropped to less than 5%, resulting in a significant increase in the proportion of soft alloys, the proportion of hard alloy greatly reduced. In the 1990s, for example, the ratio of soft and hard alloys in American aluminum extrusions was 10:1, and that in Japan was 20:1. The development of aluminum alloy profiles is fast, and its output accounts for about 85% of the entire extruded material. As the aluminum extrusion material is being developed towards large-scale, flattened, and integrated, the proportion of large profiles has been increasing, which has reached about 10% of the total output of the profile. At present, there are more than 50,000 types of aluminum profiles. Among them, there are more than 1,000 kinds of large profiles, including a variety of complex profile profiles, gradually changing profile profiles and profiled sections, large-scale integrated ribbed panels and profiled hollow profiles. The larger width of the extruded profile can reach 2500 mm, with a larger area of ​​up to 1500 cm2, a larger length of up to 25 m to 30 m, and a heavier weight of up to 2 t. The width/thickness ratio of the thin-walled wide profile can reach 150-300, and the number of holes in the hollow profile with holes can reach as many as tens. The larger outer diameter of the aluminum alloy bar and pipe is 800mm, the outer diameter of the reverse extruded pipe is 1500 mm, the smaller wall thickness of the pipe is 0.1mm, and the length is up to 1000m. As the output, variety and specification of aluminum alloy extrusion materials are continuously expanding, their application range is becoming more and more extensive.
1.1.5 Current Status of Aluminum Extrusion Technology in China
China's aluminum extrusion production was blank before 1949. After 1949, China began to establish aluminum extrusion industry, and now has established a complete extrusion industrial system, the larger water pressure extruder is 125MN, and 75MN, 80MN and 100MN and 125MN hydraulic drive are designed and manufactured separately. Extruder. The number of domestic aluminum alloy extruders has reached 3,000, and the structure and degree of automation have been greatly improved and improved. The automatic speed control devices for hydraulic presses for individual drives have reached a high level. Extrusion technology continues to innovate and extrusion processes continue to improve. The output, variety and specifications of extruded aluminum alloys continue to increase. According to preliminary statistics, in 1980, the output of aluminum alloy extruded materials in China was 152,900 tons. In 2005, it increased to more than 3.52 million tons, accounting for about 60% of the total output of aluminum materials, and the number of varieties has exceeded 10,000. The width is 932mm, the large sectional area of ​​the profile is up to 400cm2, the length is up to 10m～30m, and the 16-hole hollow wallboard profile with the width of 680mm can be extruded by the flat extrusion method. The seamless profile is produced by the special-shaped needle piercing method. Hollow rotor girder profiles, with self-designed and manufactured 670mm × 270mm × 1600mm flat extrusion cylinders and flat ingots, fixed extrusion gaskets, for the high-speed railway and subway developed a successful large-scale aluminum alloy rail vehicles and other profiles. China's current production of bar larger diameter Φ620mm, pipe specifications range Φ5mm × 0.5mm ~ Φ620mm × 115mm. Of course, compared with industrialized countries, China's aluminum extrusion technology still has a certain gap.
1.2 Development Direction of Aluminum Extrusion Technology
In the development of metal extrusion processing theory and technology need to consider the main items are: (1) reduce power consumption, energy saving; (2) reduce external friction, improve deformation efficiency; (3) improve accuracy; (4) Use anisotropy, internal stress, deformation heat treatment and other methods to improve the overall performance of the product; (5) Effective use of waste and the development of comprehensive utilization techniques to improve the recovery rate and yield; (6) To prevent defects or use defects; (7) Improve Tooling quality and service life; (8) Reduced processes; (9) Increased productivity per unit of time and labor savings to achieve high speed, automation, and continuous production; (10) Cleaner production, improved environment, and reduced labor intensity; (11) ) Lower costs and lower costs; (12) Develop new uses, new features, special features, and versatile new materials.
2 Progress of aluminum tube cold rolling technology
Pipe rolling is one of the main methods for producing seamless pipes. In pipe rolling, according to the different deformation temperatures of the pipe blanks, it can be divided into hot rolling and cold rolling. At present, in the production of aluminum tubes, hot rolling has been replaced by extrusion in most cases. The tube obtained by hot extrusion is cold-rolled to obtain a finished tube.
The surface of the pipe obtained by cold rolling is smooth, uniform in structure and performance, and accurate in wall thickness. Compared with the stretching method, the cold rolling method also has the advantages of high pass rate, high production efficiency and the like. Through the rolling method can also produce a variety of special-shaped pipe, variable section pipe, tapered pipe and other economic section pipe.
There are many kinds of cold rolling mills. At present, there are periodic two-roll cold rolling mills and periodic three-roll cold rolling mills. In addition, there are planetary cold rolling mills, continuous cold rolling mills, multi-line cold rolling mills, and transverse multi-roller spinning machines. These new cold-rolling mills have the advantages of high production efficiency, large processing rate, etc. However, due to the complex manufacture of equipment and tools, the difficulty in replacing pipe specifications, and the cost of equipment and tools, have not been widely adopted.
The periodic two-roll cold-rolling mill was first appeared in the United States, and its structure has been improved to a very good extent. The product specifications can reach the outer diameter of Φ12mm to Φ457mm and the wall thickness of 0.2mm to 15mm. Common cold-rolling mills include Russia's X ПT cold-rolling mill and China's LG cold-rolling mill.
Cold rolling mills consisting of three or more rolls are called multi-roll cold rolling mills. Multi-roll mills can be divided into three, four, and five rolls. Generally, a pipe with a diameter of Φ8 mm to Φ60 mm is rolled with four rollers and a pipe with a diameter of Φ60 mm to Φ120 mm is rolled with a four-roll or a five-roll cold-rolling tube mill.
Spinning is a method of forming a thin-walled rotating body workpiece. It uses a tool such as a revolving wheel to perform the feeding motion, and pressurizes the metal blank that rotates along the same axis along with the core mold, so that it produces continuous local plastic deformation and becomes a desired hollow rotary body part. Spinning processing includes ordinary spinning and strong spinning.
Spinning method can be used to produce dozens of alloys of dozens of sizes of pure aluminum, hard aluminum and super hard aluminum. Large-diameter thin-walled hollow rotary parts with a diameter of more than 8000 mm can be controlled and the thickness can be controlled within ±0.01 mm. Within.
The tools used for rolling and spinning pipes mainly include rollers, core rods, mandrels, and rotating wheels. The design and manufacture of these tools is one of the key technologies for tube forming. It requires the use of advanced tool steels, high-speed steels, carbides, and other materials. The hardness after heat treatment should reach HRC 60-65.
3 The progress of aluminum extrusion technology
Stretching is widely used in the production of aluminum and aluminum alloy tubes, rods, types, and wire rods. It is generally conducted at room temperature, so it is often called cold drawn.
3.1 Wire Stretching Technology
Aluminum and aluminum alloy wire can be divided into three major categories: rivet wire, electrode wire and electric wire. Wire drawing blanks generally have extruded blanks, rolled blanks and cast blanks. Aluminum wire is generally used for rolling billets and casting billets; while small batches, alloys, and rivets and wire rods with many specifications are mainly used for extrusion of billets.
In general, bars of Φ ≤ 7 mm are called wire rods, but some of them have a diameter of about 10 mm; the smaller diameter of wire rods can be determined according to the purpose, and the wire is generally about 0.5 mm, and some can be reached. Below 0.1mm. Wires can be supplied individually or in rolls.
Stretching is the key technology of stretching process. It is necessary to calculate the stretching model according to the conditions of the equipment, alloy, product variety and specifications, etc., in order to formulate a reasonable stretching process.
The wire drawing die is divided into an inlet cone, a lubricating cone, a working cone, a sizing zone, and an outlet cone. The drawing die is generally made of cemented carbide. The large-size wire die is also made of alloy tool steel. The small-size wire die is sometimes made of diamond.
In order to smoothly pass the front end of the wire blank through the die hole, the front end of the wire blank should be milled on the mill head.
Aluminium and aluminum alloy wire stretching can be performed on a single stretching machine or on multiple stretching machines. A wire drawing machine is a drawing machine where the wire passes through only one mold from the inlet to the outlet. It is mainly used to produce alloy wires with larger diameter, higher strength, and poorer plasticity. The multi-pull machine is a wire drawing machine that can continuously stretch the wire through several molds with gradually decreasing specifications, and is mainly used for producing aluminum alloy wires and pure aluminum wires with small specifications and medium strength. Modern wire drawing machines have chain drive and hydraulic drive; there are single-wire stretchers and multi-stretchers; linear stretchers, and wire-drawing machines.
3.2 Pipe Stretching Technology
Aluminum and aluminum alloy pipe commonly used in the stretching method can be divided into two categories: without core stretching (pulling) and with core stretching (lining). According to the different types of cores, the lining can be divided into short core stretching, long core stretching, floating core stretching and expanding expansion. Currently, these kinds of stretching methods are used in the world.
Pipe extrusion process points are: 1 to prepare high-quality billet, such as cast billet, continuous casting and rolling, multi-roller slanting billet, extrusion billet and secondary extrusion billet, etc.; 2 tensile mold, according to the stretching method , the alloy composition and status of the blank, equipment performance, etc., to carry out a strict calculation of the mold, to develop a reasonable process specification; 3 rational design and manufacturing tooling, pipe drawing the main tool is the mold and the core head. Tubular drawing tools, drawing dies, full-diameter dies, expanding dies and cores can all be made of hard alloys, especially in small-sized and commonly used medium-sized tools and tools. The use of cemented carbides is gradually increasing. However, it should be noted that the use of carbide dies and full-diameter dies should be properly sheathed.
Aluminum alloy pipe stretching equipment can be divided into linear stretching machine and disc stretching machine according to the pull-out products. The linear stretching machine has chain, wire rope and hydraulic three transmission methods, of which the chain stretching machine is widely used. The disc type stretching machine is suitable for the production of long tubes because it can fully exert the advantages of the moving core stretching process, but it is still rarely used in China.
The chain stretching machine has a single-stranded pipe stretcher and a double-stranded pipe puller. The modern chain stretching machine is equipped with various advanced auxiliary devices, including the feeding mechanism, the tube blank core rod mechanism, the automatic drawing of the stretching trolley, the pulling hook, the unhooking, the carriage returning to re-bite, etc., and the stretching speed can be auto-adjust.
In order to increase the production efficiency of the stretching machine, modern stretching machines are moving in the direction of multi-line, high-speed, and automation. Multi-stretching stretches three wires at the same time, with up to nine tubes. The stretching speed can reach 150m/min, and some of the processes such as loading and unloading are fully automated.
China's double-stranded pipe stretcher has formed a series of 15 specifications ranging from 5kN to 6000kN. The general specification range of aluminum and aluminum alloy pipes is Φ5m×0.5mm～Φ300mm×(3～5)mm; the smaller ones can be made of capillary materials, and the larger outer diameter can reach Φ500mm or more.
4 Aluminum alloy tube, rod, type, wire heat treatment technology and equipment
The heat treatment methods for aluminum and aluminum alloy tubes, rods, wires, and wires include annealing, quenching, and aging.
Annealing can be divided into homogenization annealing, semi-finished or intermediate annealing and finished (complete) annealing, the main purpose of which is to improve the material's plasticity or control performance level. Quenching can be divided into online quenching and off-line quenching. A sophisticated on-line gas, mist and water quenching device has been developed in foreign countries to achieve high-quality quenching of large-scale, complex hollow and solid profiles, producing asymmetrical and complex profiles up to 30m, width 1000mm and uneven wall thickness. Dimensional accuracy, shape tolerances and mechanical properties can meet the requirements of technical conditions. In-line quenching is mainly used for alloys with less susceptibility to quenching such as 6××× and 7005. In China, on-line quenching is widely used in the T5 and T6 states of 6××× alloys, but the precision on-line quenching system is still immature and is under development. Off-line quenching is to cool the extruded product into a vertical or horizontal quenching furnace and re-solution heat it, and then quickly quench it with water cooling. This is a very mature process, which can precisely control the temperature, quenching transfer time up to 15s, and can well ensure the product's performance, especially for hard alloys such as 2××× and 7×××, due to quenching. The sensitivity is very high and the solution quenching method must be used. For some products of 6×××, 4×××, 8××× aluminum alloys, the important applications should also be quenched by off-line quenching.
Time-effect can be divided into two categories: natural aging and artificial aging. Artificial aging can be divided into first-level aging, multi-level aging, over-ageing, and under-ageing. The aging process is mainly to strictly control the temperature and time.
At present, heat treatment equipment has developed rapidly. Precise online gas, fog, and water quenching devices have begun to spread around the world. The vertical quenching furnace has reached a high of 40m. Southwest China Aluminum (Group) Company has a 35m high quench furnace with a temperature difference of ±2.5°C. Horizontal quenching furnaces have also been successfully developed abroad. The aging furnace has also made great progress. At present, the world's long artificial aging furnace reaches 40m. Our country has several 30m-long artificial aging furnaces put into use, and the temperature difference can be controlled within ±3°C. The aluminum alloy ingot processing device with a 75t to 100t ingot homogenization furnace and a water-mist rapid cooling system has been widely used in the world, and China is also constructing a large homogenization furnace of 50t to 70t. A wide variety of annealing furnaces, including electric, fuel, and gas types, are commonly used throughout the country.
5 Aluminum alloy pipe, rod, type, wire material finishing and straightening technology and equipment
The process of finishing and straightening aluminum alloy tubes, rods, wires, and wires includes correction and straightening, sawing and surface treatment. Surface treatments are discussed in other papers and are not described here.
Aluminum alloy extrusion straightening is divided into pull straightening, roll straightening, twisting straightening, pressure straightening, partial straightening, and Dinggong straightening. Straightening is performed on a stretch straightening machine, mainly to eliminate defects such as bending waves and unevenness in the longitudinal direction of the product. At present, there are several types of pull levelers in the world, such as gantry type and monorail type. The large tonnage is 400 MN. It mainly stretches large section bars and profiles and thick-walled pipes. China's larger bar straightening and straightening machine is Zhongwang Group's 24MN stretching machine, which is equipped with 125MN extrusion machine. Southwest Aluminum (Group) started production of a 15MN draw straightener in 1970, supporting 125 MN hydraulic presses.
Roller leveler is mainly used to eliminate the defects such as bending, unevenness, angles that do not meet the requirements, and parallel or flared in the transverse direction of the product. At present, there are several types of roller levelers in the world, such as gantry type and cantilever type. The larger roller-height width can reach 1500 mm, some can reach 2500 mm in width, and the length can be straightened to 30m. The straightening accuracy can be achieved. Conditional requirements. In addition, 6, 7, 8, 9, and 10 roll straighteners can be used to roll the tubes and bars.
The pressure straightening machine is mainly used for partial straightening, and the large pressure straightening machine is a 5MN vertical press.
The sawing of products can be divided into scrap saws, semi-finished hot saws and finished saws. Semi-finished products are better to choose the synchronous heat saw, finished saws generally use high-speed precision saws, precision up to ± 1mm. Sawing requires accurate, smooth, and burr-free, depending on the blade.
6 Conclusion
(1) The extrusion method is still the main production method for aluminum and aluminum alloy tubes, rods, wires, and wires. Its products have large coverage, many varieties, high efficiency, excellent quality, and high added value. They are favored by people in recent years. Come, its production process technology, process equipment, tooling and die technology have all achieved rapid development.
(2) Extrusion-cold-stretching method is an important production method for aluminum and aluminum alloy tubes, rods and wires. Cold rolling, drawing process, tooling and equipment are in the direction of large-scale, precision, automation and modernization. development of.
(3) Heat treatment and straightening and straightening of aluminum and aluminum alloy tubes, rods, patterns, and wire rods are important production processes and have a major impact on product quality. In recent years, the process and equipment have made great progress.
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