What Is Aluminum Fabrication?

Aluminum processing, aluminum billets are processed into materials by plastic processing methods, the main methods are rolling, extrusion, stretching and forging. Aluminum processing began to be produced industrially in the early 20th century. Before the 1930s, copper processing equipment was basically used, and the products were mainly used in aircraft manufacturing. Since the 1960s, aluminum production has developed rapidly, with an annual increase of about 4 to 8%. Products are widely used in aviation, construction, transportation, electrical, chemical, packaging and daily necessities industries. The output is second only to steel, ranking second in metal materials. China built a larger aluminum processing plant in the mid-1950s and formed a production system. The products have been serialized and there are seven alloys. It can produce plate, strip, foil, pipe, rod, profile, wire and forgings. (Free forgings, die forgings) eight categories of products.

Aluminum processing

(Method of processing aluminum)

From the macro level of economic growth, the meso perspective of industry evolution, and the micro behavior of enterprise development, we all find that the current aluminum industry's transition 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 fees". When the total downstream demand and structural increase are rapidly increasing, companies with technological advantages, channel advantages, cost advantages, and location advantages not only have processing fees It can be guaranteed, and there is also the possibility of improvement. If the factors of capacity expansion are added together, the growth of performance will be rapid and significant.

In recent years, China's aluminum profile industry has grown rapidly and has completely developed into a highly competitive industry. As of the end of 2010, there were 824 aluminum profiles enterprises above the designated size in China. After the rapid development stage and the fierce market competition, the basic pattern was initially formed. At present, there are many manufacturers in the aluminum foil industry in China, and the industry concentration is low. No one company has a significant market share, and no one company can have a decisive influence on the development of the entire industry. In 2010, the national aluminum foil output was about 2 million tons, and there were more than 250 companies engaged in aluminum foil production, with an average output of about 80,000 tons. The average scale is small, there are many small enterprises, and there is excessive competition in the field of low value-added products. .

With China's metal doors and windows, building curtain walls, transportation,

Aluminum and

Aluminum foil can be divided into industrial

It is mainly produced by the stretching process. Products include rivet wires, electrodes and wires. Billets are produced by extrusion, rolling or continuous casting and rolling. The extrusion method produces billets with greater flexibility and better product performance. The rolling method and the continuous casting and rolling method are suitable for the production of a single alloy variety with high production efficiency.

Mainly used in aircraft and machine building. Forgings are divided into free forgings and die forgings, and the billets are cast and extruded billets. The largest die forging hydraulic press is 70,000 tons, and the maximum projected area of the forging is 4.5 m2. The critical deformation rate of aluminum alloy is about 5 to 15%. In order to avoid the formation of coarse crystals, the deformation rate of die forging should generally be greater than 15%. To reduce uneven deformation, multi-directional free forging is often used.

The usual process for the production of pipes, rods, and profiles is: firstly use hot extrusion to make blanks, and then roll (or stretch), finishing and heat treatment to make finished products. It can also be directly made into finished products by hot extrusion. Now it has been developed from short ingots to long ingots. According to the extrusion force of the extruder, a uniform diameter ingot is used. The length of profiles and pipes can reach more than 60 meters. After stretching and straightening, it can be cut to the required length. The maximum extruder for aluminum production is 20,000 tons. Can be extruded into a ribbed tube with a diameter of 800 mm. Building profiles are extruded products developed in the 1960s, which account for more than 35% of the total extruded products, 80% of which are used for door and window frames. Almost all of the building profiles are aluminum-magnesium-silicon series alloys (LD30 and LD31). This product undergoes anodizing and coloring treatment, and various color oxide films are formed on the surface, which has good corrosion resistance, and is beautiful and durable for doors and windows, and has good sealing performance. In addition to hot extrusion, cold extrusion, isothermal extrusion, no residue extrusion, and hydrostatic extrusion have been developed (see oxidation coloring of aluminum).

Extrusion of aluminum and aluminum alloys uses forward extrusion and reverse extrusion. The appropriate extrusion speed should be selected according to different alloys. In order to obtain an aluminum alloy extruded product with good structure and performance, the extrusion coefficient () of the profile and bar is greater than 8-12 when the finished product is extruded at one time, and the lambda for forging is greater than 5. Extrusion dies have a great influence on the quality of extruded products. Extruded bars and profiles are commonly used with flat dies, and tubes are usually tapered. Extruded hollow profiles and pipes with complex shapes are widely used with split die and tongue die. Some use liquid nitrogen to cool the extrusion die to extend the life of the die and ensure the accuracy of the product. One die can extrude 30 tons of aluminum. Some aluminum alloy extruded products are prone to "coarse crystal rings", that is, a layer of coarse grains appears around the product after heat treatment. High temperature extrusion can alleviate this phenomenon. Some heat-treated reinforced aluminum alloy extruded products have increased strength and reduced plasticity after solution aging treatment.

The tubing is stretched by a number of rapid and coiled stretchers. The diameter of the spools of the travelling core coil stretcher is 630-2900 mm, and the diameter of the stretched tube blank can be 40-50 mm. The tensile force of the drawn pipe is 16 to 18 tons, the stretching speed is 24 m / min, and the pass processing rate is generally 25 to 40%. The length of the pipe produced by this process can reach 6000 meters.

The heat treatment that guarantees the final performance of the product is called finished product heat treatment, which includes finished product annealing, solution treatment, quenching, natural aging and artificial aging treatment. In addition, graded aging and deformation heat treatment processes have been developed. Aging treatment not only improves the mechanical properties of the product, but also improves the stress corrosion resistance and fracture toughness of the product. Generally, the transfer time from solution heating to quenching should be controlled within 30 seconds. The cooling speed of quenching should not only ensure that supersaturated solid solution is obtained, but also not cause excessive quenching stress and bending deformation of the product. The strip coil and plate are annealed in a box furnace, well furnace, vertical plate continuous annealing furnace or air-cushion continuous annealing furnace with strong circulation ventilation. The new furnace uses a protective atmosphere. Quenching is generally heated in a salt bath. The new process uses air cushion type continuous quenching furnace for quenching.

1.2 Classification according to the force and deformation mode of the workpiece in the deformation process

1.3.2 Classification according to the force and deformation mode of the workpiece during deformation

According to the force and deformation mode (stress and strain state) of the workpiece during the deformation process, aluminum and aluminum alloy processing can be divided into rolling, extrusion, drawing, forging, spinning, forming (such as cold stamping, cold transformation) , Deep drawing, etc.) and deep processing.

1.3.2.1 Rolling

Rolling is a plastic deformation process in which a billet is pulled into a rotating roll by friction, and the cross-section is reduced, the shape is changed, the thickness is reduced, and the length is increased by the pressure applied by the roll. According to the different rotation directions of the rolls, rolling can be divided into vertical rolling, horizontal rolling and diagonal rolling. During longitudinal rolling, the rotation direction of the work roll is opposite, and the longitudinal axis of the rolled product and the axis of the roll are perpendicular to each other. It is the most commonly used method for flat roll rolling of aluminum alloy plates, strips and foils. The rotation direction is the same, the longitudinal axis of the rolled product and the roll axis are parallel to each other, and it is rarely used in the rolling of aluminum alloy plate and strip. During diagonal rolling, the rotation direction of the work roll is the same. slope. In the production of aluminum alloy pipes and some special-shaped products, two-roller or multi-roller diagonal rolling is often used. Depending on the roll system, aluminum alloy rolling can be divided into two-roll (pair) system rolling, multi-roll system rolling and special roll system (such as planetary rolling, V-shaped rolling, etc.) rolling: according to the shape of the roll Different, aluminum alloy rolling can be divided into flat roll rolling and slot roll rolling. According to different product types, aluminum alloy rolling can be divided into plate, strip, foil rolling, bar, flat bar and profile rolling, pipe and hollow section rolling.

1.3.2.2 Extrusion

Extrusion is a method of loading ingots into an extrusion cylinder and applying pressure on the metal through an extrusion shaft to extrude them from die holes of a given shape and size to produce plastic deformation to obtain the required extruded product. processing methods. The direction of metal flow is different when pressing. Extrusion can be divided into forward extrusion, reverse extrusion and joint extrusion. During forward extrusion, the movement direction of the extrusion shaft is the same as the flow direction of the extruded metal, while during reverse extrusion, the movement direction of the extrusion shaft is opposite to the flow direction of the extruded metal. According to the heating temperature of the ingot, extrusion can be divided into hot extrusion and cold extrusion. During hot extrusion, the ingot is heated above the recrystallization temperature to perform extrusion, and cold extrusion is performed at room temperature.

1.3.2.3 drawing

Drawing is that the drawing machine (or drawing machine) pulls aluminum and aluminum alloy blanks (wire blanks or tube blanks) from the mold L of a given shape and size through a clamp to obtain plastic deformation. The required processing methods of tubes, rods, shapes and wires. According to the variety and shape of the products produced, stretching can be divided into wire stretching, pipe stretching, rod stretching, and profile stretching. Tube stretching can be further divided into hollow drawing, core head stretching and swimming core head stretching. The main elements of drawing processing are drawing machine, drawing die and drawing roll. According to the stretching die, stretching can be divided into single-mode stretching and multi-mode stretching.

1.3.2.4 Forging

Forging is a processing method in which a forging hammer or press (mechanical or hydraulic) applies pressure to aluminum and aluminum alloy ingots or forging billets through a hammer or indenter to cause plastic deformation of the metal. There are two basic methods of aluminum alloy forging: free forging and die forging. Free forging is to place the workpiece in a flat anvil (or anvil) for forging; die forging is to place the workpiece in a mold of a given size and shape, and then apply pressure to the workpiece to forge and deform to obtain the required die forging .

1.3.2.5 Other plastic forming methods of aluminum

People have also researched and developed a variety of new aluminum processing methods, which are mainly:

Pressure casting methods, such as low, medium and high pressure forming, extrusion forming, etc.

Semi-solid forming methods, such as semi-solid rolling, semi-solid extrusion, semi-solid drawing, liquid die forging, etc.

(3) Continuous forming methods, such as continuous casting and continuous extrusion, high-speed continuous casting and rolling, and Conform continuous extrusion.

Composite forming method, such as lamination rolling method, multi-blank extrusion method, etc.

Deformation heat treatment method.

Among aluminum and aluminum alloy processed materials, rolled materials (plates, strips, strips, foils) and extruded materials (tubes, rods, shapes, wires) are the most widely used and have the largest output. According to statistics, the annual output of these two types of materials They account for 58% and 39% of the world's total annual output (average) of aluminum, and the remaining aluminum processed materials, such as forged products, account for only a few percent of the total aluminum output.

1.3.1 Classification according to the temperature characteristics of the workpiece during processing

1.3 Classification and characteristics of aluminum processing methods

There are many plastic forming methods for aluminum and aluminum alloys, and they are generally classified according to the temperature characteristics of the workpiece during processing and the force and deformation mode (stress-strain state) of the workpiece during the deformation process.

1.3.1 Classification according to the temperature characteristics of the workpiece during processing

According to the temperature characteristics of the workpiece during processing, aluminum and aluminum alloy processing can be divided into hot processing, cold processing and warm processing.

1.3.1.1 Hot working

Hot working refers to the plastic forming process of aluminum and aluminum alloy ingots above the recrystallization temperature. During hot processing, the ingot has higher plasticity and lower resistance to deformation. It can use smaller capacity equipment to produce products with larger deformation. In order to ensure the organization and performance of the product, the heating temperature, deformation temperature and deformation speed, the degree of deformation, and the temperature at the end of deformation and the cooling rate after deformation should be strictly controlled. Common hot-working methods for aluminum alloys include hot extrusion, hot rolling, hot forging, hot upsetting, liquid die forging, semi-solid forming, continuous casting and rolling, continuous casting and rolling, and continuous casting and extrusion.

1.3.1.2 Cold working

Cold working refers to the plastic forming process completed below a temperature at which no recovery and recrystallization occurs. The essence of cold working is a combination process of cold working and intermediate annealing. Cold working can reach the final product with smooth surface, precise dimensions, good microstructure and properties that can meet different performance requirements: the most common cold working methods are cold extrusion, cold top forging, cold rolling of tubes, cold drawing, cold rolling of strip and foil, Cold stamping, cold bending, spinning, etc.

1.3.1.3 Warm processing

Warm working is a plastic forming process between cold and hot working. The main purpose of warm working is to reduce the deformation resistance of the metal and improve the plastic properties (workability) of the metal: the most common methods of warm working include warm extrusion, warm rolling, and warm forging.