Angle iron is one of the most common forms of structural steel manufactured today. Angle iron, also frequently referred to as steel angle, is a structural component defined by its specific L-shaped cross-section. While the name “angle iron” is historical, dating back to when wrought iron was the primary material for this shape, modern versions are almost exclusively steel alloys.
Defining the Angle Iron Shape and Nomenclature
Angle iron’s unique L-shape consists of two flat surfaces, known as “legs,” that meet at a 90-degree corner. This geometry allows the material to resist significant bending forces along multiple axes, providing structural utility. The product is also commonly known in the industry as L-bar, structural angle, or angle stock. Specifications are determined by the length of the two legs and the material thickness, sometimes called the web or gauge.
Angle iron is categorized as either “equal leg,” where both sides of the L-shape are the same length, or “unequal leg,” where one side is intentionally longer than the other. This difference in leg length allows engineers to select a profile that provides more directional strength for specific load-bearing applications.
The Standard Composition: Mild Steel vs. Other Alloys
The vast majority of angle iron is made from mild steel, a form of carbon steel containing a low percentage of carbon, typically between 0.05% and 0.25%. This low carbon content makes the material highly ductile and easy to work with, offering excellent weldability for fabrication projects. A common grade used for standard structural angles is ASTM A36 steel, known for its minimum yield strength of 36,000 pounds per square inch (psi).
While mild steel is the default, specialized applications may require different alloys. Aluminum angle provides a significantly lighter component for aerospace or transportation uses. Stainless steel angles are also manufactured for environments where resistance to corrosion is paramount, such as in food processing plants or marine settings.
Corrosion protection for standard mild steel angle is often achieved through galvanization, which is a surface coating rather than an alloy change. The galvanizing process involves dipping the finished steel angle into a bath of molten zinc, creating a protective zinc layer on the surface. This zinc coating acts as a sacrificial anode, shielding the underlying steel from rust and extending its service life, especially in outdoor or humid conditions.
Where Angle Iron is Used
In building construction, angle iron is frequently used as a lintel, a horizontal support spanning the opening above a window or door to carry the weight of the masonry above. It also functions as a reinforcement component for steel frames and vertical columns.
Angle iron is a staple in general fabrication for creating shelving units, storage racks, and industrial workbenches due to its ability to handle heavy loads. In manufacturing, it is utilized for building machine frames, equipment supports, and sturdy transport racks. Smaller angle sections are employed in everyday applications like bed frames, fence posts, and as simple structural brackets to reinforce corners and joints.