What are the steel grades and shapes covered under A500 steel hollow sections?

ASTM A500 is the most widely used North American specification for cold-formed welded and seamless carbon steel hollow structural sections (HSS). Engineers, fabricators, and procurement teams reach for A500 whenever a project calls for load-bearing tube — building frames, bridges, transmission towers, equipment skids, conveyor supports, sign structures, and architectural exposed tubing. Yet the same question comes up at the quoting stage again and again: which steel grades and which shapes are actually covered under A500 steel hollow sections?

This guide walks through both halves of that question. We will look at the four grades (A, B, C, D) defined by the standard, then the four shape families it allows (round, square, rectangular, and special), and finish with practical selection notes drawn from real structural and EPC work.

1. What ASTM A500 Actually Covers

ASTM A500 / A500M is titled "Standard Specification for Cold-Formed Welded and Seamless Carbon Steel Structural Tubing in Rounds and Shapes." Two facts in that title matter:

• Cold-formed, not hot-formed. The tube is produced from steel that is shaped at or near room temperature. Cold work raises the yield strength of the base steel substantially, which is why an A500 Grade C tube is markedly stronger than a hot-formed A53 pipe of the same wall thickness.
• For structural use, not pressure or fluid service. A500 is meant for load-bearing members. If you are conveying gas, oil, steam, or water, you are in the A53 / A106 / API 5L family instead. Picking A500 for a pressure line — or picking a pressure pipe for a column — is one of the most common specification mistakes on EPC projects.

At EZ Steel Industrial's A500 product page, each tube is shipped with a mill test report that records grade, size, and heat number, so traceability from raw coil to erected member is preserved.

2. The Four Steel Grades Under A500

A500 defines four grades. Their chemical composition is broadly similar (carbon capped at 0.26% for most grades, controlled sulfur and phosphorus), so the practical differences are mechanical: yield strength, tensile strength, elongation, and whether heat treatment is required.

A few selection rules of thumb drawn from project experience:

• Grade B is the default. Most building columns, parking structures, and equipment skids specify A500 Grade B. It is the most readily stocked grade and the easiest to source in non-standard lengths.
• Grade C is the heavy lifter. When a column must carry higher axial load or a longer unbraced length, designers move to Grade C. The roughly 10% bump in yield strength reduces wall thickness or increases capacity at the same weight.
• Grade D is the cold-region choice. Grade D is mandatory for low-temperature impact performance and must be heat treated. It is more expensive and has longer lead times, so it is only specified where the design code actually requires it.
• Grade A stays light. Grade A is still useful for non-structural guardrails, fence posts, and lightweight architectural members where the higher ductility is a benefit.

For projects that mix structural tubing with other carbon-steel products — for example, when an HSS column is welded to a base plate that comes from the A36 / A572 plate family — it pays to keep all of the [carbon & carbon alloy steel](https://www.ezindustrialtube.com/products/carbon_carbon_alloy_steel/) packages on one mill test certificate. EZ Steel Industrial groups these items under a single [structure works](https://www.ezindustrialtube.com/products/structure_works/) subcategory for that reason.

3. The Shape Families A500 Allows

The standard covers four shape families, and each has its own dimensional envelope and tolerance band.

3.1 Round HSS (HSS-Round)

Round A500 tubing is the most common shape and is produced in the widest size range. Outside diameters typically run from about 1/2 in. up to 88 in. (DN8 to DN2200), with wall thickness from roughly 1.65 mm to 25.4 mm depending on the manufacturing route. Round HSS behaves predictably in compression and is favored for columns, pile sleeves, and architectural exposed members where a clean circular profile matters.

3.2 Square HSS (HSS-Square)

Square A500 tubing is widely used as columns, vertical posts, and torsion members. Standard mill sizes cover side lengths from roughly 1-1/2 in. to 16 in. (about 38 mm to 400 mm). Because all four faces are equal, square HSS is easy to connect with welded or bolted gusset plates and gives architects a tidy visual line.

3.3 Rectangular HSS (HSS-Rectangular)

Rectangular A500 tubing trades equal sides for a longer strong axis. The standard envelope goes up to roughly 300 × 500 mm (about 12 × 20 in.). Rectangular HSS is the natural choice for beams, girts, door headers, and trusses where bending governs the design rather than compression.

3.4 Special Shapes

A500 also allows elliptical, oval, and other custom profiles when the producer and buyer agree on the geometry. These are typically made to order and are used in architectural features, special-purpose machinery frames, and aesthetic applications where a standard round or square section is not sufficient.

3.5 Manufacturing Routes

Two manufacturing routes are permitted under A500:

• Welded tubing is formed from a flat steel strip, with the longitudinal seam welded by electric-resistance welding (ERW) or another accepted process. This is the most economical route and the most common in standard sizes.
• Seamless tubing is produced by piercing a solid billet, then rolling and sizing. Seamless A500 is used when the project calls for higher wall thicknesses, better uniformity under heavy loading, or when welding is not desired in the forming process.

Both routes are accepted by the standard; the grade and shape you need, not the manufacturing route, usually drives the order.

4. Tolerances, Testing, and What to Confirm on the Mill Certificate

Beyond grades and shapes, the items that most often trip up an order are dimensional tolerances and the testing regime. A500 sets tighter tolerances than most pressure-pipe standards:

• Outside dimension tolerance of about ±1% for rounds and ±0.75% on the flat side for square and rectangular sections.
• Wall thickness tolerance of about ±10% nominal.
• Straightness, twist, and corner radius limits that depend on the largest nominal dimension.

For heavy structural orders, the mill test report should always record the heat number, the grade, the dimensional results from the lot, and the results of the mechanical tests (yield, tensile, elongation). When the order is destined for a project in a cold climate, also confirm that the specified grade — usually D — is referenced on the certificate, so the heat-treatment step is visible in the traceability chain.

5. How A500 Compares to Related Specifications

A500 is often specified alongside other carbon-steel structural or piping standards. The most common comparisons:

• A500 vs. A53 / A106. A53 and A106 are pressure-pipe standards for fluid service; A500 is for structural members. The yield strength of A500 Grade C (317 MPa) is roughly 28% higher than A53 Grade B (248 MPa), which is why A500 is preferred wherever load-bearing capacity is the design driver.
• A500 vs. EN 10219. EN 10219 covers cold-formed welded structural hollow sections in Europe and mandates a Charpy impact test at -20 °C on every grade. A500 leaves impact testing as a supplementary requirement, only enforced in Grade D, so projects with European codes sometimes need to layer on additional testing when sourcing from an A500 producer.
• A500 vs. GB/T 3094. The Chinese GB/T 3094 standard covers cold-formed welded steel tubes for general structural use. Grades such as Q345 (yield ≥ 345 MPa) are close to A500 Grade C in strength, but GB/T 3094 is less explicit about low-temperature performance and dimensional tolerance bands, so the standards are not always interchangeable without a customer-side review.

6. Selecting the Right Grade and Shape Combination

For most projects, the choice collapses to a short list of decisions:

1. Load and code. Use the structural code (AISC, Eurocode, GB 50017, etc.) to set the required yield strength, then map to Grade B or Grade C.
2. Temperature and toughness. If the design temperature drops below about -30 °C or the code calls for guaranteed impact values, move to Grade D and require the heat-treatment and impact data on the certificate.
3. Member behavior. Use round HSS for compression members and exposed architectural work, square HSS for torsion and bi-axial bending, and rectangular HSS where one axis must be much stiffer than the other.
4. Procurement. Confirm size availability, length capability, and whether the mill test report is delivered with the shipment. Bundled orders for the full [carbon & carbon alloy steel](https://www.ezindustrialtube.com/products/carbon_carbon_alloy_steel/) package — including flanges, fittings, and gaskets — reduce the number of suppliers on a structural project.

7. Closing Notes

ASTM A500 is a focused standard. It covers four grades (A, B, C, D) and four shape families (round, square, rectangular, and special), produced by cold-formed welding or seamless methods, all intended for structural rather than pressure service. Once you anchor on that scope, the rest of the specification — tolerances, testing, marking, traceability — falls into place. For EPC contractors, structural engineers, and project buyers, the practical checklist is short: pick the grade from the load and temperature case, pick the shape from the member behavior, and confirm the mill test report covers the lot that is actually shipped.

EZ Steel Industrial supplies A500 hollow structural sections in grades A, B, and C in round, square, and rectangular shapes, with full mill test reports and bundled project packaging available through the [structure works](https://www.ezindustrialtube.com/products/structure_works/) category. For project-specific sizing or low-temperature Grade D enquiries, the technical team can be reached through the contact details on the website.