If you want to know about the metal Aluminum, it is the material shaping the future of automobile industry and actually other industries. The application of aluminum extrusion technology in industries is the innovation we all need.
Aluminum extrusion involves a mechanical process to change the shape and appearance of aluminum metal. The extrusion process requires an ingot or aluminum billet, which is ideal for extrusion due to its malleability.
As a result, these features have helped increase the market share of extruded aluminum profiles from to 34%.
The hot extrusion method was first invented in the early 19th century by a man named Alexander Dick. This industry has always been developing and keeping pace with modern technology over the years.
Since aluminum parts can be produced by both hot and cold aluminum extrusion methods, various industries have shown great success in extrusion methods. The emergence of the extrusion industry led to significant progress in the production of parts for various industries. With the outbreak of World War II, military and aircraft factories increased the market demand for this industry dramatically.
Aluminum extrusion was a big step for the production of highly specialized parts in various aluminum alloys, which today is constantly updating its production process. aluminum in industry
Excellent plasticity is the main feature of aluminum that makes it well suited to the process of extrusion at the suitable temperature. Only a small section of hard work is done at this temperature and finally the hot work is executed to complete the ultimate product of extruded aluminum.
Extrusion of aluminum profiles is actually a hot work process in which aluminum sheets are pressed and passed through a section with a specific shape called a mold.
The output products are included pipes, rods and aluminium extrusion profiles have a definite shape along their entire length. The primary aluminum billet can be cylindrical or rectangular, produced by semi-continuous casting. The billet may be machined and homogenized before the extrusion process.
Extrusion of aluminum profiles and sections are divided into two categories: direct extrusion and indirect extrusion.
In direct aluminum extrusion, the semen passes through the perforated chamber, in a special way, by pressing on the aluminum billet. The billet temperature is kept at a temperature of about 400 ° C.
The rate at which a material exits the aluminum mold is called the extrusion rate, which depends on the type of alloy. This rate can be a few tens of meters per minute for softer alloys such as 6000 series aluminum or less than 1 meter per minute for harder alloys such as 2000 and 7000 series alloys.
In direct extrusion, most of the pressing force, about 30%, is used to overcome the frictional force between the billet and the holding chamber. Most long profile aluminum profiles are made this way.
In the process of extrusion or indirect extrusion, the mold is placed at the end of the hollow cylinder and by moving the hollow cylinder, the mold puts pressure on the billet inside the chamber and the desired extruded product is removed from the end of the cylinder. In this method, the billet is stationary relative to the chamber, resulting in much less friction.
Indirect extrusion is mostly used to produce symmetrically shaped aluminium extrusion profiles , hard alloy aluminum pipes and rebars such as the 2000, 5000 and 7000 series which have more capacity for the worker.
Extruded aluminum, like rolling, requires a series of secondary operations. As:
Depending on the critical quenching rate of aluminum alloys and the required mechanical properties, extruders can be quenched by natural cooling, water spraying or immersion in water. The quenching process can be accompanied by natural or artificial aging.
Heat treatment can be done after extrusion of aluminum and at the end of the process. For hardened old alloys, heat treatment involves all steps: heat treatment, quenching, and natural or artificial aging.
It means smoothing and controlled traction if necessary.
Cut with a saw
An extruded aluminum profile may be rejected for the following reasons: (Rejected profile means that it either does not meet engineering standards or does not have the characteristics required by the customer).
Causes incontinence, incontinence, internal cracks and so on.
This means that either the mold or the billet is not pre-fit properly or the dimensional accuracy is not considered.
Such as improper extrusion pressure, increased friction at the bearing location, lack of speed control and etc.
Two very important and influential factors in the material flow pattern are:
You can see the four main patterns of material flow in direct extrusion in the figure below, which adds to the non-uniformity of material flow from left to right. (The following figure is one of the most famous patterns that have been mentioned in many articles and books with the focus on extrusion).
Pattern S: The highest probability of uniform material flow. In this case, the material flow is very uniform and homogeneous, and regardless of the friction between the joint of the mold chamber and the mold. This flow pattern prevails when the surface of the mold chamber and the molds are completely lubricated.
Pattern A: This state of material flow occurs when there is no friction between the billet and the chamber, but there is considerable friction at the surface of the mold and the billet. This type of material flow creates a dead zone and the deformation zone becomes slightly larger than before.
Pattern B: In this case, there is friction both between the billet and the chamber and at the surface of the mold and the billet. In addition, the dead zone is not completely rigid and can affect the flow of material to some extent, which was not the case in the previous two models.
Pattern C: The same mode B, except that the friction is very high and the shear stress in the peripheral areas, which is obviously colder, is much higher than the center. (Simply put, materials form much harder in the billet environment than in the center). The cone of the dead area is much larger in this case and extends from the top to the bottom of the billet.
The most common defect observed in aluminum extrusion operations, especially in the case of 2000, 6000 and 7000 group alloys, is the defect of forming tubes. In this case, according to the figure, a circular separation is created between the inner core and the outer area of the billet at the cross section (behind the billet).
The friction between the billet and the chamber causes the surface layers of the billet to remain in contact with the wall of the chamber, while the aluminum billet core cuts beneath it and moves forward. Due to the creation of a dead zone in this case, the material flows into a conical shape.
Cracks can be produced and spread in the center of the extruded aluminum profile, which is called the blast center or the center of the crack in extrusion. These cracks are caused by tensile hydrostatic stress in the center of the deformation zone in the mold.
In addition, the larger the feed angle of the mold, the more heterogeneous the deformation. On the other hand, in order to experience more deformation, we need to increase the contact level. Therefore, by reducing the angle of the feeder, the depth of the feeder as well as the length of the contact surface of the billet with the mold must be increased. Note the following figure.
Extrusion aluminum has the ability to make further desired changes on the cross-sectional area of the profiles and other lateral aluminum extrusion services can be applied to it during the process. For example, to create hollow internal parts, pins or punching pins are inserted into the mold.
After the extrusion process, there are several options for painting aluminium extrusion profiles surfaces, which can include aluminum anodizing services, aluminum polishing and aluminum powder paint services.
Today, aluminum extrusion is used for a wide variety of purposes, including the construction of thermal break double glazed windows, partition profiles.
These various applications are due to the beneficial properties of aluminum, from strength to rust resistance and its ability to be recycled repeatedly without loss of strength.
All these capabilities have made aluminum extrusion an acceptable and suitable solution for the increasing needs of manufacturing.
Among the aluminum extrusion services is the design and manufacture of aluminum molds. After this stage, the aluminum billet is heated to 800 ° F-925 ° F.
The aluminum billet is then transferred to a loader, where lubricants are used to prevent the billet or ingot from sticking to the extrusion press, or handle.
Using the press, a lot of pressure is applied to the billet, which causes Aluminum ingots pass through the mold with pressure. To avoid the formation of oxides, nitrogen in liquid or gaseous form enters this chamber and flows in different parts of the mold. Nitrogen creates an inert atmosphere and increases the life of the mold.
During the cooling stages, the aluminum extrusion profile passes through the receiving table or the output roller table, and finally, after opening the mold, it takes the form of a mold.
It is then placed on a cooling table. On this table, there are fans that cool the newly produced part. After the cooling process is completed, the special extruded aluminum profile is transferred to a special table for stretching and hardening, and then the hardened extrusion is transferred to the saw table.
It is cut depending on the customer’s needs. The last step is to perform Edging operations in Edge furnaces with a temperature of 180 degrees.
The change in the length of the output product is considered when the extrusion of 6063 alloy with a thin section in the form and length of the aluminum billet is done and the temperature and thickness of the bottom of the billet are determined. The following factors can cause changes in the output of the product.
Number of extruded billets Due to the high pressure and temperatures used in the extrusion, the mold faces tend to twist.
Such torsion in the mold usually occurs close to the mold output and causes the extruded profile to change of thickness in the sections of aluminum profiles, it is observed that most of the twisting occurs in the center of the mold and decreases towards the perimeter of the profile.
The degree of mold molding is a function of the temperature rise in the mold, the design of the extrusion mold and the holding tool. Increasing the billet temperature during extrusion affects the mold temperature.
Researchers have performed studies on the extrusion of aluminum. Alloys and shown that the maximum temperature in the billet occurs during extrusion, at the corner of the mold or very close to its outlet.
Due to the transfer of heat from the billet to the mold and tools and finally to the atmosphere, a certain time is required for the mold temperature to reach a steady state during a certain length of the billet and a certain temperature from it and also at a certain extrusion ratio.
In such cases, the aluminum extrusion mold reaches a certain degree of hardness. As the temperature in the mold increases, its hardness decreases. This is due to the relationship between the hardness of steel 1113 and temperature. Due to the reduction in hardness, more twist is expected in the mold.
The extrusion of metals and the function of each of the extrusion sections of aluminum are as follows.
The production of aluminum parts by extrusion method has many advantages that certainly cannot be covered in all its angles in such a short article, but we can mention a few important cases.
One of the advantages of this process, compared to other shaping methods, is the high ability to produce parts with complex cross-sections, as well as shaping the piece at brittle and fragile angles, which according to the design with other methods can certainly not be used in these angles and twists. Parts acquired.
Homogeneity of parts produced
This method also creates high quality and smooth cross sections and makes the material stronger. In the aluminum extrusion method, the raw materials not only do not lose their physical capabilities, but this method also helps to further convex and shape the structure of the aluminum alloy.
Extrusion production is more beneficial for applicants and producers in terms of financial and associated costs in the production process. Other methods of producing aluminum parts, according to studies, have put more pressure on manufacturers in terms of financial burden.
Very high production power and efficiency
Extrusion presses آل Aluminum alloys, this ability has been seen in their design to produce continuous shifts continuously and without interruption, and this is one of the tangible advantages of this method in the production of aluminum parts.
Given that the temperature and pressure in the production of parts with the same design and design are constant and these two variables in a certain period of time in the evolution of each other produce parts.
Therefore, all parts have a very high quality integrity, which leads to the output of products with the best quality level in terms of appearance and technical characteristics.
Extrusion, in the service of the environment
In aluminum extrusion, there is no industrial wastewater and smoke and production takes place in a clean environment. Aluminum extrusion has no waste and effluent, and therefore this method reduces environmental pollution.
Steps in the extrusion industry of aluminum alloys
Forming aluminum alloys in the aluminum extrusion industry is a specific process that enters the mold by pressure with hydraulic force and leaves the mold as extruded products in different shapes. Extrusion rods are made in certain sizes and powers, this difference is directly related to the size of the billet that must be extruded.
The 4000 press with LOEWY brand, which is made in the USA, is the most powerful press of the aluminate industrial production complex. This press can produce all groups of alloys. The nominal daily production capacity is between 20 and 40 tons of profile types. Of course, this statistic varies in some alloy groups. Press 4000 has the ability to produce pipes up to 410 mm in diameter and belts up to 400 mm wide.
One of the unique capabilities of this press is the production of seamless pipes in the aluminum extrusion industry. This press has the ability to extrude the billet from 8 inches to 18 inches. Next to this huge press, there is a 500 ton stretching machine that is responsible for pulling the sections produced by the 4000 press.
Aluminum billets are the main raw materials in the extrusion industry of aluminum alloys. Billets in different diameters and alloys are produced by smelting furnaces and depending on the needs and production plan, which is announced by the production planning department. They are cut and delivered to the extruder billet preheating operators.
The billets are first raised to 380 ° C in preheated furnaces that are either electric or gas, depending on the type of extruded alloy, which are driven into the ROM by the loader after confirmation of the billet temperature by a quality production supervisor.
All kinds of frictional forces during the aluminum extrusion process increase the pressure on the hydraulic press. Due to the tension friction between the mold and the billet, smoothing must be done between the two, which is very important. Lubrication between the billet and the mold is done in different ways and has a great effect on reducing the pressure of the machine and the pressure on the mold.
After the billet temperature reaches the desired and standard production level, the billet is coated with graphite using graphite to prevent it from sticking to the mold. Graphite also plays a lubricating role. Graphite types play an important role in the set of vital requirements in the optimal production by extrusion.
At this stage, the billet is transferred to the container. The container of the device is made of several thick layers and is usually able to withstand very high radial stresses.
The ROM then pushes the billet forward until the billet enters the container, then the trap is placed behind the billet and the mandrel presses on the billet by the force of powerful hydraulic cylinders. Due to the applied pressure, the temperature rises and paste-like materials pass through the mold and form the shape of the profile.
When aluminum passes through the mold, liquid nitrogen is passed around the mold, which increases the life and durability of the mold. When the extruded material is removed from the press, the desired temperature is controlled and adjusted by sensors installed in the press.
The main purpose of knowing the temperature is to perform extrusion operations at maximum speed. The amount of heat output of aluminum extrusion depends on the aluminum alloy.
After the extrusion operation, the product is transferred to the hot table and cut by powerful saws in this section and quickly transferred to the cold press table. After the hot cutting stage, the parts are cut by the cold saw according to the lengths specified in the production coordinates.
They are cut and delivered to the heat treatment, anodizing or packaging and transportation sections, depending on the continuation of the work program.
Temperature is one of the main pillars of extrusion production of aluminum alloys. When the temperature rises, the stress of the material decreases and, of course, the extrusion operation becomes easier.
On the other hand, increasing the temperature and not controlling and closely monitoring the under during production may bring the billets to the melting temperature and cause material wastage.
On the other hand, when we increase the speed of the ROM, it increases its pressure and temperature. At lower ROM speeds, the heat generated for transfer has more time. To reduce production waste, temperature, pressure and speed must be controlled at all stages of production. The complexity of the relationships between these three variables has made the aluminum extrusion tolerance very high and controlling them helps to produce the desired profile.
One of the most important factors influencing the extrusion process of aluminium extrusion profiles is the role of the mold and, of course, the role of hot-rolled steel in mold making.