ASTM A500 grades

A500 defines four grades — A, B, C, and D — distinguished primarily by their tensile requirements, with minimum yield and tensile strength rising from Grade A through Grade C. Grade D carries its own requirements and, uniquely in the family, requires heat treatment. The exact strength values, and the fact that round sections and shaped (square/rectangular) sections carry different yield requirements within the same grade, are controlled content in the purchased standard.

Commercially — as a typical market observation, not an ASTM requirement — Grade C is the most common current North American production grade for square and rectangular sections, and much of the market ships with dual certification (meeting both B and C); this is consistent with Steel Tube Institute producer guidance and with AISC design tables assuming Grade C for shaped HSS. In our purchasing experience, Grade A is rarely stocked and Grade D typically carries special-order lead times because of its heat-treatment requirement. Availability varies by region and supplier; confirm with your service center.

The grades share the same shapes, size range, and manufacturing provisions. What changes is the required strength level and, for Grade D, the mandatory heat treatment. Because the yield requirement differs between round and shaped sections within a grade, always read the certification against the shape you are buying.

• Grade selection interacts with the design standard — confirm what your structural calcs assume
• Dual-certified B/C material is common; the mill test report states what was met
• Do not assume a stocked size is available in every grade

A mill test report for dual-certified material lists the measured chemistry and tensile results and identifies every grade the heat satisfies. Design to one grade and record it; taking credit for the higher strength of a dual-certified stick is a design decision that belongs to the engineer of record, not the purchasing department.

If your project requires traceability, state the certification requirement on the order rather than assuming a report will follow the material through distribution.

The most frequent errors we see in practice: writing “A500” with no grade and letting the supplier choose; carrying Grade B forward from an old drawing when current production has typically moved to C; assuming round and shaped sections of the same grade have the same yield requirement; and specifying Grade D without confirming the typically longer heat-treatment lead time with the producer.