ASTM A500 structural tubing, explained

ASTM A500/A500M covers cold-formed welded and seamless carbon steel structural tubing in round, square, rectangular, and special shapes, for welded, riveted, or bolted construction of bridges and buildings and for general structural purposes. In typical North American practice — reflected in Steel Tube Institute and AISC design resources built around A500 product — it is the specification most commonly cited when a drawing calls out a hollow structural section (HSS). That is a market observation, not an ASTM requirement; the governing specification is always the one on your drawing.

The two decisions that matter most on an A500 order are the grade (A, B, C, or D — each with different strength requirements, and Grade D requiring heat treatment) and the shape and size, because those drive design capacity, availability, and cost. Everything else — tolerances, testing, certification — follows from stating those clearly against the current edition.

The specification's scope covers tubing produced in welded and seamless sizes with a periphery of 88 in. [2235 mm] or less and a specified wall thickness of 1.000 in. [25.4 mm] or less. Welded product is made from flat-rolled steel by the electric-resistance-welding (ERW) process; the longitudinal butt joint must be welded across its thickness so the structural design strength of the section is assured.

A500 is a structural specification: its qualification basis is tension and flattening testing, chemistry limits, and workmanship — not the surface-finish and dimensional-refinement emphasis of a mechanical tubing specification such as ASTM A513. Selecting between the two by nominal size alone, without confirming the governing specification, is a common and avoidable purchasing error.

The standard itself notes that A500 product may not be suitable for dynamically loaded elements in welded structures where low-temperature notch toughness (typically measured by Charpy impact testing) matters. Other ASTM standards with CVN requirements — including A1085 with its optional Charpy supplement — may be more suitable there.

• Cold-formed welded (ERW) and seamless carbon steel structural tubing
• Round, square, rectangular, and special shapes
• Four grades: A, B, C, and D — Grade D requires heat treatment
• Structural design qualification, not mechanical-tubing surface or dimensional refinement

For building work in the United States, the design standard (such as AISC 360) and the project specification usually determine which grade you order. As a typical market observation — consistent with Steel Tube Institute producer guidance and current AISC design tables, which assume Grade C properties for shaped HSS — Grade C is the most commonly produced grade for square and rectangular HSS, and material is frequently supplied dual-certified against Grade B. None of this is an ASTM requirement: confirm what your local service centers actually stock before designing to a less common grade.

Grade names in A500 are strength classes, not manufacturing routes. Unlike ASTM A513's Types 1–6, an A500 grade does not tell you how the tube was made — welded and seamless product can both be certified to the same grade.

Identify the standard and edition, grade, shape, outside dimensions, wall thickness, length, quantity, certification, and any supplementary requirements. Because the inch-pound and SI systems in A500/A500M are separate standards, state which applies — the inch-pound units govern unless the “M” designation is specified in the order.

The specification and ordering guide on this site walks through each line item and the questions a producer or service center will ask if you leave it out.

Start at the grades page if you are selecting a strength class, or the shapes page if you are choosing between round, square, and rectangular sections. Use the comparison pages when weighing A500 against A513, A53, or A1085. Use the calculator for theoretical weight, the tolerances page to understand dimensional acceptance, and the manufacturing page to understand how cold-formed structural tube is actually produced.