The content of this article explains the use, manufacture, and types of aluminum channels.
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An aluminum channel is a structurally sound metal component that is made by the extrusion process to produce shapes, forms, and designs for a wide variety of applications. The major benefit of aluminum channels is their weight, which is one third the weight of steel without sacrificing durability and reliability. Aluminum channels have inside radius corners that give them their channel shape.
There are an endless number of ways that aluminum channels can be used, especially where corrosion resistance and lightweight materials are needed. They are commonly found in store mounting fixtures, framing to protect edges and faces, LED light applications, and framing for truck beds. There are two alloy grades of aluminum that are used for aluminum channels, which are 6061 and 6063.
Several types of aluminum channels are available that can be cut to any size to fit the needs of a variety of applications and come in thicknesses from 0.01 inch to as high as 5 inches. The versatility and adaptability of aluminum channels are why they are so widely used in construction projects.
Aluminum channels are the best choice for applications that require strength with the extra benefit of corrosion resistance. Since they can be configured, shaped, and adapted to fit any application, they are one of the most commonly used construction materials.
Angle aluminum channels form a right angle and are the least complex but most cost effective form of aluminum channels. They are an extruded shape made from a variety of aluminum alloys. Aluminum angle channels have several uses but are widely used as trim and finishing. They can have several types of finishes to enhance their visual appeal.
Aluminum angle channels can be found on the edge of roofs, handrails, and the corners of buildings. Due to aluminum’s corrosion resistance and its ability to withstand harsh weather, angle aluminum channels are used to seal corners of buildings as a means of protection.
The right angle corner of angle trim can be squared to form a sharp right angle or round to form a smooth angle, as seen in the image below. The legs of the right angle on angle channels can have varying lengths ranging from 1//8 inch up to 4 inches.
The shape of all C channels is mostly the same. There are variations in the types of interior and exterior corners and flanges. The three basic types of C channels are Aluminum Association, American Standard, and Canadian. C channels for the Aluminum Association are thicker with rounded corners on the inside. With American Standard C channels, the rounded corners have flanges that progressively get thinner toward the top.
Another version of C channels has the initial U shape with a web and flanges. Additionally, the tops of the flanges are bent inward, leaving a space between them to place a nut channel. As with U channels, C channels have a variety of web widths and flange lengths that can be seen in the images below.
C channels can be used to protect the edges of millwork, be an addition to wood panels, used as store fixtures, and framing. In many cases, C channels are used as an aesthetic addition to a project to give the project a sophisticated appeal.
The profile of a F shaped aluminum channel has the appearance of the letter F. In some ways, a F channel resembles a U channel with an extended web that does not have a flange. One of the flanges of a F shaped channel is positioned like a U channel on its edges. The second flange is a distance down from the first flange from which the web extends. The length of the extended web varies depending on the design of the channel. This is also true for the web distance between the flanges.
The many varieties of H aluminum channels are used for decorative and structural purposes. They are a very stable channel that makes them ideal for use for railings, trim, and door frames. H aluminum channels come with several types of finishes, which adds to their adaptability as a decorative and aesthetic touch.
Aside from their use for appearances, H aluminum channels can be used for structural purposes because of their stability, durability, and design. They come in different widths, wall thickness, and design features such as battens to enhance their hold.
H aluminum channels are available in a lower case h shape and the upper case H. Lowercase h channels are used to stretch a ceiling system by being attached to the perimeter of a room.
Furring is a construction method used to level walls and ceilings with furring channels. A hat channel has a hat shaped profile with two horizontal flanges that are used for the furring process to fur out walls, masonry walls, or ceilings. They are a corrosion resistant framing component with exceptional durability and resilience that completes the furring process. Hat channels have a high strength to weight ratio and are an affordable structural component.
Hat channels and Z channels are used to level uneven walls and ceilings since they have the added benefit of providing protection for interior and exterior framing from fire, moisture, and corrosion. Aside from their protective characteristics, hat channels assist in keeping buildings structurally sound by preventing unevenness in walls and ceilings.
The I shape aluminum channel looks very similar to H channels, with the exception that it is used as an I beam. It is known as the American Standard I beam and has rounded edges. The web is very wide, while the flanges that cross the web are shorter by comparison. The durability, sturdiness, and resilience of I channels make them ideal as cross beam supports.
J aluminum channels are a vital part of vinyl siding projects and are used to mount siding on corners. They are necessary for every corner of a house where siding meets the ground, roof, and openings. J channels provide an airtight barrier against ambient weather conditions and are easy to install since they require minimal tools, which creates a cost savings in labor and materials.
The various uses of J aluminum channels have increased since its introduction in the 1950s. The J shape of J aluminum channels is due to the 90o bend on one side of its framing profiles.
T slot aluminum channels have one or more T shaped slots where T shaped attachments can fit and be able to slide up and down. The use of T slot channels allows for the creation of complex configurations without the need for clamming or welding. T slot channels assist in eliminating the costs of riveting and welding since they can be easily connected using mounting bolts.
As with all aluminum channels, T slot channels have excellent durability with the ability to be removed, changed, and reconfigured, which is not possible with permanently welded metals.
U shaped aluminum channels are one of the most common forms. The wall thicknesses of U shaped channels vary according to how they will be used, with thicknesses ranging from 1/16 inch up to 1/4 inch. A U shaped channel is defined by its web and flanges or its bottom and sides. Both parts of a U shaped channel can be of different dimensions, such as a short web with long flanges or a wide web with short flanges, as seen in the diagram below.
In Z shaped aluminum channels, the legs or flanges extend in opposite directions from the web to create the Z profile. They are used for metal roofing or for wood roofing in unique or unusual situations. Z channels act as receivers for panels, ridge caps, and headwall flashing and prevent leaks due to their directional installation. They are used as replacements for J channels because they are a little smaller than the width of panels.
There are numerous varieties of Z channels, with some being referred to as clips while others are bars. Clips have a very small web, while bar Z channels have the typical Z profile.
The ten basic aluminum channels described here are only a sampling of the many aluminum channels that are available. Each year new and unique shapes are being discovered that are increasing the use of this highly durable and useful product.
Aluminum, since the beginnings of its mass production, has become a vital part of construction and industrial and commercial products. Its excellent strength to weight ratio as well as its appearance has made it the number one choice for a variety of projects. Also, aluminum is in line with the environmental concerns of the 21st century due to its ability to be recycled, repurposed, and reused multiple times.
Most attractive to builders and designers is aluminum’s low cost, making it possible to produce complex and intricate products at prices that fit consumer budgets. Regardless of the many positive features of aluminum, a vital part of its production is the many available finishes.
There are a couple of reasons designers and engineers decide to have aluminum finished.
Aluminum produces an oxide film when it is exposed to the air. In most cases, this is sufficient for protection against corrosion and harmful conditions. When faced with extreme environments, it is necessary to have additional protection, which can be provided by the proper finish.
The application of a finish allows designers to choose an appearance that best fits their designs. The wide variety of aluminum channels makes it possible to add them as a finishing touch or highlighted feature. The proper finish then becomes an additional positive quality.
There are a wide variety of mechanical methods used to finish aluminum channels. The purpose of mechanical finishing can be to create a smoother surface or pattern. The types of mechanical finishes include:
The process of pretreating is used in conjunction with strip cleaning prior to the coating process. It can be completed chemically or by an electrolytic process. The chemical process is the most common to satisfy various federal regulations and the needs of architectural, construction, and transport applications. The pretreatment process is performed with precision to avoid contamination of the aluminum surface.
Pretreatment offers these functions and benefits:
Although pretreatment may seem to be a minor part of aluminum channel processing, it serves a necessary and important function.
Bright dipping is a chemical process for polishing aluminum before being anodized and enhancing aluminum channels. It is a process that is performed at high temperatures and must be strictly controlled to ensure the proper chemical balance between nitric acid, phosphoric acid, aluminum in suspension, gravity, and temperature.
The outcome of bright dipping is a very high and bright luster to aluminum channels. The harder the temper of the aluminum alloy, the brighter the finish will be. The process smooths the surface of the aluminum at the microscopic level but does not remove scratches or other blemishes. For aluminum channels, the process is normally performed on aluminum alloy 6063 T6.
As with some of the other processes, anodizing is an electrochemical process but is more passive than the more aggressive chemical methods. The outcome of anodizing is the conversion of the substrate of the aluminum channel to a layer of aluminum oxide. Aluminum has a natural oxide layer that forms when it is exposed to the air. The natural layer of oxide is uneven and thin, offering inconsistent protection.
The application of a controlled electrical charge in an acidic electrolytic bath creates a regular and uniform layer of oxide for better protection from corrosion and wear. The addition of anodic layers allows aluminum channels to undergo secondary processing, such as the use of colorants and lubricants.
Regardless of its drawbacks, liquid paint remains an option for finishing aluminum channels. For liquid paint to be applied, the surface of aluminum channels has to be pretreated with sprays to adhere to the paint. The choice of liquid paint includes a richer and wider array of colors that are brighter and more distinctive. The choices of paints include acrylics, polyester, silicone polyester, and polyvinylidene fluoride (PVDF).
The choice of a liquid paint for aluminum channels is dependent on the amount of corrosion resistance required and the needs of the application. In the case of aluminum angles for building construction, liquid paints can include paints that match the colors of the sides of the structure.
Powder coatings of aluminum channels are ideal for protecting them from harm from the elements as well as deterioration from corrosion. It is a combination of phosphates and metal particles. The types of coating materials vary from one producer to another with the overall effect of the coating being the same. Aside from the exceptional protection from corrosion, powder coatings protect aluminum channels from rust and the results of exposure to harsh weather.
The application of a powder coating does not prevent the application of paint to the surface of aluminum channels and comes in a variety of colors. A powder coating can last as long as twenty years without needing to be replaced or refinished.
Aluminum is the second most used metal for construction after steel. Channels in the shapes of C, J, and U are the most commonly found in construction projects due to their tensile strength, reliability, and sturdiness. All aluminum is alloyed with other metals to enhance its durability and performance. Every alloy has a number and is designed to serve a particular function.
The various grades of aluminum are numbered from 1 to 8, with one being unalloyed while the other seven grades are alloyed with other metals such as copper, magnesium, silicone, zinc, and nickel. The combinations of alloyed metals enhance the properties of raw aluminum and give it different characteristics.
Grade 6063 has medium strength and is commonly used for the extrusion of aluminum channels. It can be extruded into shapes with thin walls that are very small. The lustrous finish of grade 6063 has made it an excellent choice for architectural projects.
Aluminum grade 6063 is known as the architectural alloy due to its high tensile properties, excellent ability to be finished, and an exceptionally high degree of corrosion resistance.
The silicon content of 6063 makes the grains of the alloy finer, which increases 6063’s fluidity. Its magnesium content gives it strength and endurance.
The properties of 6063 include:
As with 6063, the alloying elements of grade 6061 are silicon and magnesium at percentages of 1% for magnesium and 0.6% for silicon. This combination of alloys makes 6061 resistant to corrosion, stress, and cracking and gives it good formability and weldability. Aluminum grade 6061 is used for structural applications due to its superior strength.
Grade 6061 has all of the same features and characteristics as grade 6063 in regard to its weldability, corrosion resistance, and being able to be coated and polished. Unlike grade 6063, 6061 is not easy to bend or cold work and requires a great deal of force to be shaped. Cold forming of aluminum grade 6061 requires great care and precision to ensure quality and proper performance.
Grade 7075 is a high strength aluminum alloy with good stress corrosion cracking resistance. It is widely used in the aerospace industry due to its excellent strength to weight ratio. When grade 7075 is subjected to below zero temperatures, its strength increases. The primary alloy ingredients of grade 7075 are zinc and copper mixed with magnesium, iron, silicon, manganese, chromium, and titanium, which are included in small quantities.
Much like other grades of aluminum, grade 7075 can easily be anodized. It has a high machinability rating, meaning that it can be shaped, chipped, and manipulated. Of the aluminum alloys, grade 7075 is the most durable, corrosion resistant, and resistant to cracking. Unlike 6063 and 6061, grade 7075 is not able to be welded except using special welding processes.
Grades 6063 and 6061 are the two most popularly used aluminum alloy grades, with grade 7075 being used for its strength, endurance, and other factors. These three alloys are not the only ones used to make aluminum channels. Other grades include 2024, 5083, 7050, 5086, 5456, and 6082. The manufacture of aluminum channels provides for the selection of the correct alloy necessary to meet the needs of an application.
There are five aluminum temper classifications: F, O, H, W, and T that indicate the class of treatment. The letter designation is followed by a number to indicate the strength or depth of the treatment. The temper designation is added to the alloy number to let producers and users know what mechanical properties have been added to the alloy
In the case of aluminum grades 6063 and 6061, they will have a tempering designation of T-5 or T-6, indicating the grade of thermal treatment they have received.
The most common method for the formation and production of aluminum channels is extrusion, which is a process where an aluminum alloy is forced through a die that has the cross sectional profile of the channel. The process of extrusion is very simple and lacks complexity. It involves applying force to the raw alloy and pushing it through a hole or profile in the shape of the aluminum channel.
There are two types of aluminum channel extrusions: solid and semi-hollow. A solid extrusion is without voids or openings such as angle channels. Semi-hollow extrusions are partly closed voids such as C channels.
The process for extrusion begins with a round die made from high grade steel. For most common aluminum channels, the dies already exist and simply need to be pulled from storage. The die is preheated to 400o C up to 500o C to maximize its useful life and ensure even metal flow. Once the die is at the appropriate temperature, it is placed in the extrusion press.
Aluminum for the manufacture of aluminum channels comes in the form of solid cylindrical blocks or billets. They are heated to 750o C up to 930o C to make them malleable for the extrusion process. The heating process heats the billet to a point just below its melting point to make it pliable enough to be forced through the die.
The malleable heated billet is mechanically transferred to the extrusion press where it is treated with a release agent or lubricant before being loaded. The release agent or lubricant aims to prevent the billet from sticking to the ram or the die.
The loading process for the billet can be seen in the diagram below. The billet is loaded into the extrusion press chamber and forced through the die. The flow direction in this example is from left to right, with the extruded aluminum channel exiting on the right.
The force of the hydraulically driven ram is applied at up to 15,000 tons of pressure to push the billet through the die. As the pressure rises, the billet material expands, filling the walls of the extrusion chamber and is crushed against the die. The force makes the billet smaller and wider until it completely fills the chamber leaving the soft aluminum only one place to go, which is through the die. The desired shape is squeezed out to form the fully shaped aluminum channel profile.
As the extruded channel emerges from the die, it is gripped by a puller that guides it along with the runout table. Part of the movement along the runout table involves quenching or cooling the channel using a water bath, spray mist, air, or fans. Once the channel has reached the length of the table, it is cut by a hot saw to make room for the next extrusion.
The extrusions are mechanically removed from the runout table to a cooling table where they sit until they have cooled to room temperature. During the extrusion process twisting will have occurred to the profiles, which has to be removed. The imperfections caused by the twisting and turning of the channels are corrected by a stretching and straightening process.
Stretching and straightening are achieved by a mechanism that grips the aluminum channel at either end. It is then pulled and stressed until it is fully straight and brought to the proper tolerance and specifications.
When the extrusions have reached room temperature, they are cut to the appropriate lengths by the finishing saw, which are normally circular saws.
After the aluminum channels are cut to length, multiple processes may be applied including anodizing, powder coating, and aging. The final stages of processing are dependent on the final purpose of the channels and the types of protection they will need.
Since the introduction of aluminum at the beginning of the twentieth century, it has become an important part of many aspects of society, from aluminum cans to structural I beams for buildings. The unique characteristics of aluminum, being very light but strong, has made it easy to conform it to a variety of applications.
A crucial and essential use for aluminum is channels that are used as the structure for display cases, corners for buildings, and decorative touches for architects. The versatility and durability of aluminum channels has made them a central part of engineering plans and designer diagrams.
The varying characteristics of aluminum channels have made them a valuable and critical solution for different processes and applications.
Aluminum has twice the conductivity of copper by weight, making it an ideal material for use in large capacity overhead power lines.
The malleability of aluminum gives the impression that it isn’t very strong. Actually, its malleability is what makes it so useful and versatile. Unlike other metals, aluminum maintains its strength regardless of the conditions, while other metals become brittle in cold weather and are vulnerable to corrosion. It has one third the weight of steel with a better weight to strength ratio. Aluminum channels are ideal for conditions where lightweight load bearing is necessary.
One area where aluminum channels are widely used is in conditions where weight and rigidity are necessary for protection. Aluminum channels have a greater and more substantial advantage over copper for those conditions.
Much of the selection of aluminum channels for construction projects is based on aluminum’s high resistance to rust and corrosion. While other metals may become weathered and suffer wear in harsh conditions, aluminum channels can endure and maintain their strength.
Aluminum channels are used in modern electronics due to its inability to be influenced by applications where magnetic properties can cause failures and problems.
Aluminum channels are safe to use in applications that are highly flammable or potentially explosive.
In the modern era, all raw materials are assessed for their ability to be recycled, which has become a major social, commercial, and industrial thrust. This aspect of aluminum is one of the reasons that it is so widely used since aluminum components, parts, and channels can be returned to manufacturers for repurposing, reprocessing, and remanufacturing as raw materials.
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