Structural steel is metal used in construction materials. Fundamentally, it is defined as steel optimized for use in building construction—differentiated from a steel grade one might use to engineer tools, or stainless steel popularly used in kitchen surfaces and appliances.

Structural steel is generally a carbon steel, meaning it has a chemical composition containing both iron and carbon. Structural steel is any category of steel with a carbon content of up to 2.1% of its total weight. The higher the carbon content, the higher a piece of steel’s yield strength—meaning it is less ductile, or less likely to bend or warp when pressure is applied.

A wide variety of shape options further allow structural steel products to support building and design. The shape is integral for the correct distribution of load weights and pressures, with the proper selection ensuring that a building is durable and safe. Different shapes of structural steel each have unique mechanical and chemical properties that make them appropriate for different applications. These shapes include:

Angles.
These perpendicular, L-shaped cross-sections, either with equal or unequal legs, are commonly found in corners of structures and other places to supplement main pillars and beams.

Tubing.
Hollow tubing made from hot-rolled steel coils and sold in round, square, and rectangular shapes is easily fabricated and welded according to need. It's a lightweight structural alternative to solid structural steel products.

I-beams.
II-These beams are one of the most common structural steel products for both beams and columns. The two parallel elements of the "I" or "H" cross-section are known as flanges, and the connecting element is known as the web.

Wide flange beams.
With a much longer web than in I-beams, the flanges of a wide flange beam are almost perpendicular to the web.

Channels.
Structural channels are hot-rolled into a C-shape, which, like I-beams, have a wider angle of attachment between the flanges and the web. They provide structural support in addition to a main load-bearing beam, most commonly for bracing or framing.

Plates.
Carbon-steel plates can withstand massive amounts of weight and pressure, making them perfect for ocean vessels. These are heavy-duty, wide surface areas of solid, continuous structural steel meant to span large areas.

Bars.
Short for merchant bars, these are hot-rolled and cold-finished carbon types of bars with different properties, dimensions, and shape sub-categories, such as round, square, and flat cross-sections.