Classification And Dimensions of Channel Steel Materials

Definition and Core Characteristics of Channel Steel

Channel steel, also known as U-channel or C-channel, is a long strip of steel with a U-shaped or C-shaped cross-section, classified as a complex-section steel product. Its distinctive geometry consists of a vertical web with two horizontal flanges projecting from the same side, creating a trough-like profile. This cross-sectional design provides an excellent strength-to-weight ratio, making channel steel a preferred material in construction, mechanical engineering, and vehicle manufacturing. The open channel shape also features a flat back surface on the web, which facilitates easy bolting or welding against other structural members. Channel steel is manufactured primarily through hot rolling, with raw material billets consisting of carbon structural steel with carbon content not exceeding 0.25%, or low-alloy steel billets. The material is required to possess good welding, riveting, and comprehensive mechanical properties to meet the demands of structural applications.

Classification of Channel Steel by Production Method and Profile Type

Channel steel can be classified into two main categories based on the manufacturing process: hot-rolled channels and cold-formed channels. Hot-rolled channels are produced by heating steel billets to high temperatures and passing them through rolling mills to achieve the desired U-shaped cross-section. Cold-formed channels are manufactured by bending flat steel strips at room temperature through a series of forming rollers, and they can be further divided into equal-side channels, unequal-side channels, inner-coiled channels, and outer-coiled channels. Within the hot-rolled category, channels are further classified by flange geometry. American Standard C-channels feature tapered inner flange surfaces with a slope of approximately 16.67% (2-in-12), while MC-channels (Miscellaneous Channels) have wider or deeper flanges that fall outside the standard C-series proportions. European channels include UPN profiles with tapered flanges and UPE profiles with parallel flanges. Chinese standards classify channels as ordinary channels and light channels (designated with "Y"), with specified inner arc radii for leg edges.

American Standard Channel Sizes: C-Sections and MC-Sections

Under the American standard system (ASTM A6/AISC), structural channels are designated by the letter "C" (for standard channels) or "MC" (for miscellaneous channels), followed by the nominal depth in inches and the weight per foot in pounds. For example, C8×11.5 indicates a channel with a nominal depth of 8 inches weighing 11.5 pounds per foot. C-channels are produced in depths ranging from 3 to 15 inches. Common C-channel sizes include C3×4.1 (3.00 inches deep, 1.410 inch flange width, 0.170 inch web thickness) through C15×50 (15 inches deep, 3.716 inch flange width, 0.716 inch web thickness). MC-channels offer wider flange options for heavier structural demands; common sizes range from MC6×12 to MC18×58. For metric applications, C-channel dimensions are also available in millimeter designations. For instance, C75×6 has a depth of 76mm, flange width of 35mm, and weighs 5.9 kg/m; C150×12 has a depth of 152mm, flange width of 51mm, and weighs 12.2 kg/m; and C380×74 has a depth of 381mm, flange width of 95mm, and weighs 74 kg/m.

European Standard Channel Sizes: UPN and UPE Profiles

European standards (EN 10279 and EN 10365) define two primary channel profiles: UPN (tapered flange channels) and UPE (parallel flange channels). UPN channels have a U-shaped cross-section with tapered inner flanges and slightly outward flange tips, distributing material efficiently to balance weight against structural performance. The size range for UPN channels extends from UPN 50 to UPN 400, with the number indicating the nominal depth in millimeters. The web thickness for UPN profiles typically ranges from 6 to 8.5mm. UPE channels share the same U-shaped cross-section but feature parallel flanges, which simplify bolted and welded connections and reduce fitting time on site. UPE profiles range from UPE 80 to UPE 400, with web thicknesses of 4.5 to 5.2mm. The tapered flange geometry of UPN channels provides a slender profile suitable for architecturally exposed steelwork, while the flat flanges of UPE channels make them ideal for applications requiring precision fit-up and numerous beam-to-channel connections.

Chinese Standard Channel Sizes: GB/T 707 Specifications

Under the Chinese national standard GB/T 707, channel steel is designated by model numbers representing the nominal height in centimeters. For example, a "5#" channel has a nominal height of 50mm, with corresponding flange width and web thickness specified in the standard. The size range covers models from 5# to 40#, with common dimensions including: 5# (50mm height, 37mm flange width, 4.5mm web thickness), 6.3# (63mm height, 40mm flange width, 4.8mm web thickness), 8# (80mm height, 43mm flange width, 5mm web thickness), and 20# (200mm height, 73mm flange width, 7mm web thickness). Within the same height designation, there are typically multiple variants distinguished by letters such as "a" and "b", representing different flange widths and web thicknesses. The Japanese Industrial Standard JIS G3192 specifies SHF series channels, with SHF100 having a height of 100mm, flange width of 50mm, and web thickness of 5mm. Chinese channels are prioritized for cost efficiency in infrastructure applications, while JIS channels are optimized for seismic resistance. GB standard channels are available in lengths typically ranging from 6 to 12 meters.

Material Grades and Quality Standards

Channel steel is manufactured from various material grades depending on the regional standards and application requirements. Under ASTM standards, ASTM A36 is the most commonly specified grade for structural carbon steel channels, offering a minimum yield point of 36 ksi (250 MPa) and tensile strength of 58–80 ksi (400–550 MPa), with a maximum carbon content of approximately 0.26%. For higher strength requirements, ASTM A572-50 (50 ksi yield) is a common alternative. Other available grades include ASTM A529-50, A529-55, and A992. Under European standards, common grades include S235JR, S275JR, and S355JR. Chinese standards specify grades such as Q235, Q235B, and Q345B. Japanese and other international standards include SS400 and SM400 series grades. For stainless steel applications, channel sections are available in grades 201, 304, 316, and 316L. The selection of material grade depends on the required yield strength, environmental exposure, weldability, and cost considerations for each specific application.