Aluminum profile processing
Aluminum processing, using plastic processing methods to process aluminum ingots into materials, mainly including rolling, extrusion, stretching, and forging. Aluminum processing began to be produced industrially in the early 20th century, and before the 1930s, copper processing production equipment was basically used, with products mainly used in aircraft manufacturing. After the 1960s, aluminum production developed rapidly, with an annual growth rate of approximately 4-8%. The products were widely used in industries such as aviation, construction, transportation, electrical, chemical, packaging, and daily necessities. The output is second only to steel and ranks second in metal materials. In the mid-1950s, China built a relatively large aluminum processing plant, forming a production system. The products have been serialized, with seven alloy series available, capable of producing eight types of products including plates, strips, foils, pipes, bars, profiles, wires, and forgings (free forgings, die forgings).
Chinese name: Aluminum Processing
The main methods include rolling, extrusion, stretching, and forging
Purpose: To process aluminum ingots into materials using plastic processing methods
The product is mainly used for aircraft manufacturing
catalogue
1 Development
2 Introduction
3 Melting and Casting
▪ smelt
▪ casting
- Production of foil materials
5 Wire production
6 Forging production
7 Other productions
8 Related processes
develop
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From the macro perspective of economic growth, the meso perspective of industry evolution, and the micro behavior of enterprise development, we have found that the current trend of the aluminum industry moving from primary electrolytic aluminum smelting to deep processing will become an inevitable trend. Aluminum processing products are generally priced in the form of “aluminum price+processing fee”. When there is a rapid increase in downstream demand and structural increment, companies with technological advantages, channel advantages, cost advantages, and location advantages can not only ensure their processing rates, but also have the possibility of increasing them. If combined with capacity expansion factors, the growth of performance will be rapid and significant.
In recent years, China’s aluminum profile industry has grown rapidly and has fully developed into a fiercely competitive industry. As of the end of 2010, there were 824 aluminum profile enterprises above designated size in China. After rapid development and fierce market competition, the basic pattern has taken shape. At present, there are many aluminum foil production enterprises in China, with low industry concentration. No enterprise has a significant market share, nor can any enterprise have a decisive impact on the development of the entire industry. In 2010, the national aluminum foil production was about 2 million tons, with more than 250 enterprises engaged in aluminum foil production, with an average output of about 8000 tons. The average scale was relatively small, and there were many small enterprises, resulting in excessive competition in the low value-added product field.
With the rapid development of China’s metal doors and windows, building curtain walls, transportation industry, chemical industry, power equipment industry, national defense and military industry, the demand for aluminum profiles will continue to grow. At the same time, new products, new processes, and new uses of aluminum profiles will continue to emerge, promoting technological progress and sustained healthy development of the industry. From 2011 to 2015, the aluminum profile industry will still show a good development trend.
With the rapid growth of China’s aluminum profile industry, the sales revenue of the aluminum profile industry will also increase year by year. According to statistical data, from 2005 to 2010, the compound annual growth rate of sales revenue in China’s aluminum profile industry was 35.20%. Based on the current domestic and international economic situation, combined with sales revenue data of China’s aluminum profile industry from 2005 to 2010 and China’s economic growth data, it is roughly estimated that the compound annual growth rate of sales revenue of China’s aluminum profile industry from 2011 to 2015 is 20%. In 2015, the sales revenue of China’s aluminum profile industry will reach 1.0498 trillion yuan. With the rapid development of the downstream industry of aluminum foil, its demand for aluminum foil will continue to increase. By 2012, the consumption of aluminum foil will reach 1.8 million tons, and by 2013 it will reach 2.1 million tons, with a compound annual growth rate of 17% from 2011 to 2013.
brief introduction
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The plastic processing of aluminum and aluminum alloys should ensure that the product achieves stable, consistent required dimensional accuracy, mechanical properties, and good surface quality. Attention should also be paid to preventing mechanical damage and corrosion, controlling grain size and microstructure. These quality requirements are mainly ensured by production processes and equipment. Aluminum and its alloys generally have good plasticity and are easy to plastic process. The phase composition of hard aluminum is complex, with brittle structures such as low melting phase and intermetallic compounds. Its plastic processing has some characteristics, such as homogenization treatment to eliminate internal stress and intragranular segregation generated during ingot cooling; The surface of the ingot needs to be milled to remove surface segregation caused by low melting phases. Some aluminum alloys also need to be coated with aluminum to improve their corrosion resistance and processability. Aluminum alloy has overheating sensitivity and the heating temperature must be strictly controlled.
Melting casting
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smelt
It provides ingots for plastic processing. Smelting furnaces often use gas or oil reflector furnaces, with a general capacity of 20-40 tons or more; Resistance heating reflex furnaces are also used, with a capacity of generally around 10 tons. In order to shorten the furnace loading time, improve melting efficiency, reduce gas absorption and oxide film entrapment, tilting top loading circular furnaces have been adopted in industry. It is best to use rapid analysis instruments to analyze the alloy composition during melting and adjust it in a timely manner. To ensure the purity of the melt, prevent harmful gas pollution, and control chemical composition, in addition to shortening the melting time as much as possible, it is advisable to cover it with powdered flux mainly composed of potassium chloride and sodium chloride, with a general dosage of 0.4-2% of the weight of the furnace charge. The melting temperature is usually controlled between 700-750 ℃.
After melting, the metal needs to be refined and filtered to remove harmful gases such as hydrogen and non-metallic inclusions, in order to improve the purity of the metal. Refining usually uses solid refining agents or gas refining agents. Solid refining agents are generally dominated by chlorides, and refining agents using hexachloroethane instead of chlorides are also used. In the early days, chlorine gas with strong activity was used as a gas refining agent. Although the purification effect was good, it caused serious environmental pollution. Therefore, nitrogen chlorine mixed gas, inert gas, and three gas (N2, Cl2, CO) refining agents were developed with good results. To ensure the refining effect, the oxygen and moisture content in the refining gas should generally be less than 0.03% by volume and 0.3 grams per cubic meter, respectively. The dynamic vacuum degassing method also has good degassing and sodium removal effects.
Filtering is the process of passing molten metal through a filter made of neutral or active materials to remove suspended impurities from the melt. Glass wire mesh, microporous ceramic tubes and plates, and alumina particles are commonly used as filter beds for filtration. Electric flux refining and flux layer filtration can also be used.
casting
Casting generally adopts vertical or horizontal water-cooled semi continuous casting method. To improve the microstructure and surface quality of vertical casting ingots, electromagnetic crystallization groove, low crystallization groove, and hot top casting method have also been developed (see metal solidification). The water-cooled semi continuous casting method is to introduce liquid metal into a water-cooled crystallizer through a flow channel, allowing the liquid metal to cool and form a solidified shell. The ingot is then pulled out of the crystallizer by the base of the casting machine or uniformly lowered by its own weight to form a billet. The process parameters vary greatly due to differences in alloy composition and ingot size. Generally, the casting speed and cooling speed should be increased as much as possible, and the height of the crystallization tank should be reduced. The casting temperature is usually 50-110 ℃ higher than the liquidus line of the alloy. In addition, the continuous casting and rolling process of aluminum strip has also been developed.
Plate and strip production adopts flat roll rolling, with basic processes including hot rolling, cold rolling, heat treatment, and finishing. For hard aluminum alloys such as LY12 and LC4 with complex chemical compositions, homogenization treatment should be carried out before hot rolling. The processing temperature is generally 10-15 ℃ lower than the eutectic temperature of the low melting point phase in the alloy, and the insulation time is 12-24 hours. The aluminum cladding of hard aluminum alloy is achieved by placing aluminum clad plates on both sides of a milled ingot and using hot rolling welding. The thickness of the aluminum coating layer is generally 4% of the thickness of the sheet metal. Hot rolling is generally carried out above the recrystallization temperature. Hot rolling can be carried out on a single stand reversible rolling mill or on multiple stands for continuous rolling. To improve the yield and production efficiency of large ingot rolling, ingots weighing 10-15 tons or more should be developed. Factories with an annual output of less than 100000 tons generally use four roll reversible hot rolling and adopt hot rolling technology, with a hot-rolled strip thickness of about 6-8 millimeters. Factories with a production capacity of over 100000 tons often adopt single stand, two stand, three stand, or five stand continuous rolling after the four roll reversible hot rolling mill is opened, and carry out hot finishing rolling. The thickness of the strip can reach 2.5-3.5 millimeters. Hot rolled strip is used as a cold-rolled billet after being coiled. To ensure optimal plasticity of the metal, hot rolling should be carried out in a single-phase microstructure state. The hot rolling temperature for LY11, LY12 and other alloys is 400-455 ℃. The deformation rate of the first few passes is generally within 10%, and gradually increases thereafter. The deformation rate of pure aluminum and soft aluminum alloys can reach 50%, while that of hard aluminum alloys is around 40%. The total deformation rate of hot rolling can reach over 90%.
Cold rolling is often carried out at room temperature, and thin sheets and strips with precise dimensions, smooth and flat surfaces can be obtained through cold rolling, as well as work hardened sheets and strips with specific mechanical properties. Cold rolling mainly adopts the strip method production process, using four roll reversible rolling mills or four roll irreversible rolling mills for cold rolling. Currently, irreversible rolling mills are being developed for cold rolling. The rolling mill is equipped with hydraulic pressing, hydraulic bending rolls, automatic thickness control system or automatic thickness control system for measuring roll gap, and plate shape control instrument. It is controlled, recorded, and stored by a microcomputer to obtain plate and strip with precise dimensions and flat plate shape. For example, the tolerance of 0.18mm strip can reach ± 5 microns. Small factories also use the block method to produce sheet metal. The cold deformation rate of aluminum after annealing can reach over 90%. Multiphase hard aluminum alloy has obvious cold work hardening and requires intermediate annealing. The cold deformation rate after intermediate annealing is 60-70%. Hot rolling uses lotion lubrication, and cold rolling has developed from lotion to full oil lubrication. Adopting a multi-stage cooling system with individually controlled nozzles to reduce friction between aluminum plates and rollers, cool rollers, control roller profiles, wash away aluminum powder and other impurities to achieve good surface quality and plate shape.
After cold rolling and heat treatment, the strip is often refined on a roll straightening machine or on a continuous straightening machine train. The flat quenched plate should be processed within the aging incubation period, usually completed within 30-40 minutes after quenching. The total deformation of the quenched plate during flat calendering should not exceed 2%.
The successful continuous casting and rolling of aluminum plates and strips in 1955 can produce thin plates and aluminum foil blanks. China began using this method to produce thin plates in the early 1970s.
Production of foil materials
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Aluminum foil can be divided into industrial aluminum foil and packaging aluminum foil. Industrial aluminum foil has a relatively pure chemical composition and a thickness of 0.005-0.2 millimeters. It is mainly used as a capacitor, insulation material, moisture-proof material, etc. in the electrical and electronic industries. The thickness of packaging aluminum foil is generally 0.007-0.1 millimeters, and there are various products such as flat foil, printed foil, colored printed foil, and laminated aluminum foil. It is mainly used as packaging material for food, tea, paper cigarettes, etc. The minimum thickness of aluminum foil produced by strip production method can reach 0.0025 millimeters, and the width can reach 1800 millimeters. Aluminum foil rolling is seamless rolling, and the rollers are always in an elastic flattened state. During rolling, the thickness of the foil material is controlled by adjusting the rolling force, rolling speed, and controlling the tension. During rough rolling, the rolling force is used to control the thickness of the foil material; During precision rolling, the thickness of the foil material decreases with the increase of rolling speed; The greater the tension, the smaller the thickness; To prevent breakage, the tension is usually selected as 0.2-0.4 of the conditional yield strength σ 0.2 of the foil material. During low-speed rolling, “thick oil” or “thin oil” is often added to the lubricating oil to adjust the rolling thickness of the aluminum foil. Lubricants and rolling mill conditions have a significant impact on the quality of foil materials. The aluminum foil blank comes from cold-rolled aluminum coils, which are generally pre annealed at 340-480 ℃ with a thickness of 0.4-0.7 millimeters. The deformation rate during rolling is about 50%, and the total deformation rate can reach over 95%. Foil materials with a finished thickness of less than 0.01-0.02 millimeters should be rolled together and double layered.
wire rod production
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Mainly produced using stretching technology. The products include rivet wires, welding rods, and wires. The billet is produced by extrusion, rolling, or continuous casting and rolling methods. Squeezing method produces billets with high flexibility and good product performance. Rolling method and continuous casting and rolling method are suitable for the production of billets of a single alloy variety, with high production efficiency.
Forging production
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Mainly used in aircraft and machine manufacturing. Forged parts are divided into free forgings and die forged parts, and their blanks are cast and extruded blanks. The largest forging hydraulic press is 70000 tons, and the projected area of the maximum forging size is 4.5 square meters. The critical deformation rate of aluminum alloy is about 5-15%. To avoid the formation of coarse grains, the deformation rate of forging should generally be greater than 15%. To reduce uneven deformation, multi-directional free forging is often used.
Other production
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02:15
Incredible metal extrusion process, the coin sized aluminum sheet was stretched into a 20 centimeter high aluminum bottle
The usual production process for pipes, bars, and profiles is to first use hot extrusion to make billets, and then roll (or stretch), finish, and heat treat them to make finished products. It can also be directly produced into finished products by hot extrusion method, which has now developed from short ingot to long ingot extrusion. According to the extrusion pressure of the extruder, a uniform diameter ingot is used, and various profiles and pipes are extruded by the splitter combination die and tongue die. The length of the product can reach more than 60 meters, and after stretching and straightening, it is cut into the required length. The maximum extruder used for aluminum production is 20000 tons. Can be extruded into ribbed tubes with a diameter of 800 millimeters. Architectural profiles are extruded products developed in the 1960s, accounting for over 35% of the total extruded products, of which 80% are used for door and window frames. Almost all building profiles are made of aluminum magnesium silicon alloys (LD30 and LD31). This product undergoes anodizing and coloring treatment, forming various colored oxide films on the surface, with good corrosion resistance, making doors and windows beautiful, durable, and well sealed. In addition to hot extrusion, methods such as cold extrusion, isothermal extrusion, residue free extrusion, and static liquid extrusion have also been developed (see aluminum oxidation coloring).
Aluminum and aluminum alloys are extruded using forward and reverse extrusion methods. The appropriate extrusion speed should be selected based on different alloys. In order to obtain aluminum alloy extruded products with good organization and performance, the extrusion coefficient (λ) of profiles and bars is greater than 8-12 during a single extrusion process, and the λ of billets used for forging is greater than 5. The extrusion die has a significant impact on the quality of extruded products. Flat molds are commonly used for extruding bars and profiles, while conical molds are commonly used for pipes. Hollow profiles and pipes with complex shapes are widely extruded using splitter combination molds and tongue shaped molds. Some use liquid nitrogen cooling extrusion molds to extend mold life and ensure product accuracy. One mold can extrude 30 tons of aluminum material. Some extruded products of aluminum alloys are prone to “coarse grain rings”, which means that after heat treatment, a layer of coarse grain area appears around the product. High temperature extrusion can alleviate this phenomenon. After solid solution aging treatment, some aluminum alloy extruded products that can be strengthened by heat treatment have increased strength but decreased plasticity.
The pipe stretching adopts multiple rapid and drum stretching methods. The diameter of the moving core head coil stretching machine drum can reach 630-2900 millimeters, and the diameter of the stretched pipe blank can reach 40-50 millimeters. The stretching force of the pipe is 16-18 tons, the stretching speed is 24 meters per minute, and the processing rate is generally 25-40%. This process can produce pipe lengths of up to 6000 meters.
relational process
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The heat treatment that ensures the final performance of the product is called finished product heat treatment, including finished product annealing, solution treatment, quenching, natural aging, and artificial aging treatment; In addition, graded aging and deformation heat treatment processes have been developed. Time treatment not only improves the mechanical properties of the product, but also enhances its stress corrosion resistance and fracture toughness. The transfer time from solution heating to quenching should generally be controlled within 30 seconds. The cooling rate of quenching should ensure the acquisition of supersaturated solid solution while not causing excessive quenching stress and bending deformation in the product. Rolling and sheet metal are carried out in box type furnaces, well type furnaces, vertical sheet metal continuous annealing furnaces, or air cushion continuous annealing furnaces with strong circulation ventilation
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