With its close tolerances, good finish and dense structure, square steel tube is favoured for many mechanical applications across a wide range of industries such as construction, automotive and agriculture. They offer a high strength-to-weight ratio at a relatively low cost. No matter your use case, steel tubes are easily welded, drilled, formed or punched.

Some other examples of square tubing applications are building construction, railings, and signposts. In construction, square tube steel is used for frameworks, support columns, and bridge components due to its ability to bear heavy loads and resist deformation. When it comes to railings and fencing, square tubing delivers a clean, modern appearance while providing durability and safety. In signage, the structural integrity of square tube steel ensures long-lasting support for signposts in outdoor environments. They are measured by their outside dimensions and their wall thickness.

Square Tube Metal Types

Square tube is available in the following metal types:

Aluminum – Looking for something lightweight and resistant to corrosion? Aluminum square tubing is the superior choice. This extruded aluminum is commonly found in fabrication projects such as support columns, gates, handrails, etc. You can identify an aluminum square tube by its square corners, inside and out, with no visible weld seam.

Mild Steel – Made from low-carbon steel, mild steel square tube is easy to machine, weld, and form. Its consistent square shape and uniform wall thickness provide stability and load-bearing capacity, which are essential for construction projects such as building frameworks, support columns, and railings. Its high strength-to-weight ratio makes it suitable for industrial applications, including automotive components, agricultural equipment, and machinery.

Stainless Steel – Stainless steel tubing is ideal for any structural application requiring greater strength and corrosion. Its durability and ability to withstand harsh conditions make it a preferred choice for construction, marine, and chemical processing industries. It can also be used in fabrication projects in chemical, acidic, fresh and saltwater environments. Stainless steel square tube is particularly suitable for applications in food processing and pharmaceutical industries, as its non-reactive nature ensures hygiene and safety.

How Square Tube is Manufactured

There are three main methods for manufacturing tubing:

Seamless – Can be Produced Through Extrusion

Seamless square tube is created using a solid steel billet that is heated and then pushed or pulled over a form to make a hollow structure without any welded seams. This process can also involve extrusion, where the heated billet is forced through a die to shape the tube. The absence of welded seams gives seamless tubes superior structural integrity, making them ideal for high-pressure applications and environments. Seamless square tube is commonly used in oil and gas, aerospace, and heavy machinery manufacturing industries.

As-Welded – or Electric-Resistant Welded (ERW)

In the “as-welded” process, also known as electric resistance welding (ERW), steel sheets are rolled into a square or rectangular shape and then fused along the edges using electrical resistance. Although the welded seam can be a point of weakness in some cases, modern welding techniques ensure high-quality bonds that meet industry standards. As-welded square tube is commonly used in construction, furniture manufacturing, and many other structural applications where extreme strength is not required.

Draw-Over-Mandrel (DOM)

DOM square tube is produced by taking an electric resistance welded tube and drawing it over a mandrel (a precision steel rod) while passing it through dies to achieve tighter tolerances, improved surface finish, and a more uniform structure. This additional process removes the weld seam flash, effectively giving it the appearance and qualities of a seamless tube. DOM tubing is suitable for demanding applications in industries such as automotive (e.g., hydraulic cylinders), machinery, and robotics.

Which process is used depends on the metal type. Aluminum tubing is either extruded or cold drawn. Stainless tubing can be welded — roll-forming strips of stainless steel into a tube shape and then welded (same as hot rolled welded) — or seamless (through the extrusion process).

Whether you are looking for square aluminum tubing, stainless steel square tubing or even square steel tubing, we have it all. We carry many stock lengths, but can also cut the square tube steel to fit your exact specifications.