Steel tubing size options include rectangular, round, and square. Structural carbon steel shapes are ideal for construction. The variety of shapes available, from I-beams to angle, as well as pipes and tubes all have high cross-sectional stiffness due to their second moment of area. Structural shapes can come in many materials, carbon steel is a good choice for when your project requires a high strength material and low-luster isn’t a concern. Our most popular structural grade is ASTM A500 carbon steel tubing. ASTM A500 is a standard specification for cold-formed welded and seamless carbon steel structural tubing in round, square and rectangular shapes. A500 is the most common specification in North America for Hollow Structural Sections (HSS).

Carbon Steel Tube and Pipe Properties and Composition:

As the carbon content rises, steel has the ability to become harder and stronger through heat treating, but this also makes it less ductile. In carbon steels, a higher carbon content reduces weldability and lowers the melting point.
Steel is commonly considered carbon steel when no minimum content is specified for any alloying element (for example, aluminum, chromium, nickel, molybdenum, vanadium, etc.) or any other element added to obtain a desired alloy effect. The manganese does not exceed 1.65%, the specified minimum for copper in not below .40% or exceed .60% and silicon does not exceed .60%.

Carbon levels are divided as follows:

• low carbon = .06% to .25% carbon content (mild steel)
• medium carbon = .25% to .55% carbon content (medium steel)
• high carbon = >.55% to 1.00% carbon content (hard steel)

Carbon grades are available in the following grade series:

• 10XX = non-resulpherized carbon steel, with manganese 1.00% maximum (for example 1018, 1045 and 1050).
• 11XX = resulpherized carbon steel (for example 1117, 1141 and 1144).
• 12XX = rephosphorized and resulpherized carbon steel (for example 12L14 and 1215)

The second two numbers in AISI-SAE designations indicate the approximate carbon content for steel (for example, in 1018 the carbon range is .15% to .20%; .18% [shown as "18"] is the approximate carbon content).