This article will take an in-depth look at steel channels.
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This chapter will explore the concept of steel channels, their manufacturing process, and the reasons steel is chosen for channel construction.
Steel channels are "C"-shaped hot-rolled carbon steel sections featuring a vertical web and rounded corners on the top and bottom flanges. They include a wide web and two flanges, which can be either parallel or tapered. The strength and durability of steel make it an ideal material for manufacturing metal channels.
Steel channels are utilized for their structural strength in constructing building frames, braces, and supports for various machines and heavy equipment. In the construction industry, they are employed to reduce sound by placing them between the two sides of plasterboard walls. The channels help attenuate sound waves by dampening vibrations caused by sound on either side of the wall. This is just one of many applications for steel channels, which are renowned for their toughness and durability.
A steel channel is a component made from hot-rolled mild steel, featuring interior corners with a defined radius. This design imparts the necessary strength and rigidity for supporting steel angles and various building applications. With the appropriate tools and dimensions, steel channels are relatively straightforward to fabricate. They are typically produced according to ASTM A36 dimensional standards.
After hot-rolling, steel channels often undergo additional inline fabrication processes. They are coated or galvanized to enhance their resistance to corrosion. Steel channels can be cut, drilled, or machined to meet specific requirements and are also readily weldable. Large channels are frequently produced using the laser fusion technique.
Steel is considered the optimal material for manufacturing metal channels due to its excellent mechanical properties.
Roll shaping a sheet or strip of metal produces metal channels. Roll forming is the process of continuously bending a metal strip as it goes between a series of rollers, also known as supports, that distort a piece of the metal until the required shape is attained. After the shaping and configuring is completed, the formed parts are cut to the desired lengths. Roll forming is a low-cost method for mass-producing parts that don't require any extra processing or finishing. Roll forming allows for the creation of an infinite number of metal channel profiles.
Hot rolling is a metalworking process conducted above the recrystallization temperature of the material. This method often results in mechanical properties that are unidirectional and can introduce deformation-induced residual stresses. Additionally, non-metallic inclusions may sometimes affect directionality. Residual stresses frequently arise from non-uniform cooling, which is typical in shapes with irregular cross-sections, such as I-beams and H-beams.
Cold rolling involves rolling the metal at temperatures below its recrystallization temperature, typically at room temperature. This process enhances the surface finish and maintains tighter tolerances. It utilizes four-high or cluster mills due to the smaller size and increased strength of the workpieces compared to hot-rolled materials. Common cold-rolled products include sheets, strips, and rods, which are generally smaller and more precise than their hot-rolled equivalents.
All roll-formed products, including metal channels, begin with a computer-aided design (CAD) that includes details such as geometry, length, and metal design features. The objective is to present the design as a unified structure to simplify manufacturing. CAD’s flexibility allows the part to be created by either inputting its dimensions or drawing it directly within the software.
The software produces a nested and separated representation of the metal channel based on the provided data. These diagrams illustrate the part's development through each stage of the roll forming process. The roll forming progression data can be directly extracted from CAD and converted into G codes, which are then used by a CNC roll forming machine.
The initial stage of the roll forming process involves placing a coil of metal onto an uncoiler, also referred to as a decoiler. The decoiler supplies the roll of sheet metal to the roll forming machine in a continuous feed. In the image below, the uncoiler or decoiler is positioned to the right of the roll forming machine.
Inline pre-processing often involves punching slots, holes, notches, or custom designs into metal channel roll-formed parts. A programmable machine—whether mechanical, pneumatic, or hydraulic—uses hardened tools with sharp cutting edges to apply force to the metal sheet.
The roll forming machine is equipped with precisely engineered dies in each stand to facilitate the roll forming process. These specialized tools are designed to meet the exact specifications of the metal channel being formed. The roll forming dies are arranged in stations, with each station featuring a roller that progressively shapes the metal sheet.
The roll forming process starts once the dies are installed in the machine and the CAD program is uploaded. As the metal strip comes out of the uncoiler, it undergoes pre-processing before being directed onto an entry guide or table, which ensures it enters the first pass in a square and straight manner. This step is crucial for ensuring the quality of the final product. Depending on the complexity of the metal channel, the process may involve anywhere from a few to thirty or more passes.
Roll forming can begin and end in various ways. Some processes start with straightening, while others perform this step at the end. Once the channel has been formed, the finished length is fed out and cut to precise specifications before being collected on a table or set of rollers, regardless of the method used.
Steel channels are produced by transforming steel into linear roll-formed channel shapes using high-speed roll forming techniques. The shapes and dimensions of these channels are tailored to meet the specific requirements of their intended applications. Steel channels serve various functions, such as providing continuous support and reinforcement for other components.
The process begins with a basic design consisting of a web and legs on both sides. During roll forming, metal strips are shaped into different configurations specifically designed for their intended uses. Steel channels are most commonly found in C channel structures.
In what used to be just a flying cutoff die operation, inline post fabricating can now comprise a variety of die operations. Inline post-fabrication dies may now perform all the hole punching and other notchings previously performed in the pre-punch process. This decreases the number of dies needed and enables tighter tolerances on the notching sites without the distortion that would occur if the U channel or J channel was pre-punched and then bent.
Achieving tight tolerances and higher speeds in inline fabrication requires advanced inline flying die accelerators and die boosters equipped with precise length measurement systems for post-punching and pre-punching presses. The die accelerator can perform up to 12 different functions within a single die, running pre-punching and post-punching/cutoff presses concurrently. J channel thicknesses can vary from 0.003" to 0.150".
Thicknesses up to 0.250" are feasible with 1/4 and 1/2 hard aluminum. When a thickness greater than 0.030" is needed, certain decorative pre-coated metals are generally not recommended unless larger-than-standard corner radii are acceptable. Some coatings, like pre-finished Hot Dip Galvanized coatings, can be used up to 0.125" thick. Special tooling costs may arise for unique corner radii, Ampco bronze for highly polished stainless steel that cannot be covered with a protective strippable PVC, or legs bent to angles other than 90 degrees, along with other advanced forming requirements.
Tooling is typically necessary when there are returns at the top of each leg, unless the size corresponds to existing dies. New dies might be needed for Z channels with a short web between the legs, though these are generally less costly than those required for channels with longer webs. Z channels are especially prevalent in the framing and metal building industries. Although Z channels can have similar inward flanges, this is not a common feature.
In other industries, these channels are known as Purlins. Some channels are so large they are referred to as panels. Purlins can be made from various metals, including aluminum and stainless steel, and are typically pre-finished with coatings like galvanized or other rust-resistant finishes.
C channels are among the most common types of metal channels, used for supporting structures such as buildings, walls, roofs, and ceilings. Roll-forming can be used to create C channels in a variety of specific shapes, sizes, and dimensions, all reflecting the channel's C-shaped profile.
Modern inline post-fabricating processes can now incorporate multiple die operations, extending beyond the traditional flying cutoff die. Post-fabrication dies handle hole punching and notching that were previously done during pre-punching. This advancement reduces the need for multiple dies and allows for tighter tolerances on notching positions, minimizing distortion compared to pre-punching followed by bending.
For precise tolerances and increased speed in inline fabrication, advanced inline flying die accelerators and boosters are employed. These systems utilize precise length measurement tools in both post-punching and pre-punching presses. A die accelerator can execute up to 12 distinct functions within a single die while simultaneously managing pre-punching and post-punching/cutoff operations.
C channels and box channels typically have thicknesses ranging from 0.003" to 0.150". Metal C channels and aluminum box channels can achieve thicknesses up to 0.250" with 1/4 and 1/2 hard aluminum. For metal thicknesses exceeding 0.030", decorative pre-coated metals are generally not recommended unless larger corner radii are used.
However, up to 0.125 mm of coating can be utilized, such as a hot dip galvanized coating that has been pre-finished. The length of a box channel or a C channel can range from 3 to 15 feet (9 to 4.5 m) within close tolerances, up to 40 feet (12 m) long.
A hat channel consists of two horizontal outward flanges (the brim) and two vertical flanges. From a three-dimensional view, the top of a hat channel displays a flat, horizontal surface. It features a square base with either straight or angled sides. The sides flare outward from the center toward the top, resembling the profile of a wide-brimmed hat. Similar to a C channel, a hat channel begins as a U shape in the roll forming process, with the top edges bent outward. Its design and structure make hat channels ideal for roof framing applications, and they are commonly referred to as hat purlins, which are key components in roof structures.
A metal U channel formed through roll forming, featuring a horizontal bottom web and two vertical legs with outward flanges, is referred to as a hat channel. The outward flanges are sometimes called wings or fins. Because hat channels require minimal forming, they can be produced with lower tooling costs compared to many other roll-formed products. They can be formed with widths up to 19" and thicknesses up to 0.060", or with widths up to 14" and thicknesses up to 0.150".
Hat channels can be as small as 0.250" wide when the material is thin enough to be roll formed. Hat channels can be roll-formed to be as high as 5.25" and as low as 3/16"; and even less with thinner metals. There is no need for blind or air forming while roll forming hat channels; hence, tight tolerances are easy to achieve. As a result, the roll dies used to produce the hats will completely enclose all sections of the headwear. Other, more intricate profiles require blind or air shaping to create the desired shape.
A J channel's configuration is achieved by making one of the channel's sides longer than the other, resulting in a profile that resembles the letter J. Although the basic J channel comes in a range of sizes and applications, other types of J channels are tailored to meet specific application needs. Simple J channels without a hem, hemmed J channels, and J channels with a flat part that can be screwed or nailed on are the three most frequent types.
This section will explore the various applications, uses, and advantages of steel channels.
Steel channels can be used as rafters on light-duty roofs, running from the eaves to the ridge and providing support for the roof deck. Steel channel, rather than wood rafters, allows smaller and lighter rafters to sustain the same weight. Steel channel is stronger, lasts longer than wood, and is resistant to rot, fungal decay, and moisture. I-beams are commonly used as rafters and ridges on heavy-duty roofs, and a steel channel is installed perpendicularly on top of the rafters every few feet from the ridge down to the eave. The steel channel bridges the spaces between the rafters, allowing them to be spaced further apart, and also serves as an attachment point for the steel deck.
Solar panels must be lightweight yet durable enough to survive extreme environments. Metal channels are appropriate in these situations since they meet both requirements. Metal channels' tensile strength ensures that they can withstand the harsh conditions in which solar panels are mounted. Metal channels are lightweight, allowing solar panel manufacturers to install their goods in a wide range of situations.
Steel channel is a "C"-shaped hot-rolled carbon steel built with a vertical web and inside radius corners on the top and bottom horizontal flanges. Steel channels consist of a wide web and two flanges, which could be parallel or tapered. Steel's strength and durability make it excellent for use in the production of metal channels.
A steel channel is a structure made of hot-rolled mild steel. The interior corners of steel channels have a specified radius. This provides the strength and rigidity it needs to sustain steel angles and building projects. With the correct equipment and proportions, they're fairly simple to prepare. Steel channels are usually manufactured to ASTM 36 dimensional specifications.
It is thus critical to choose a steel channel cognizant of the steel channel type, its characteristics, applications, and benefits.
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