What does the H in A36 H-Beam signify regarding its production standard?

The "H" in "A36 H-Beam" signifies the product form or shape, not a sub-grade of A36 chemistry. It indicates that the A36 material has been rolled into a specific structural shape with an "H" or "I" cross-section (wide flange beam). The production of these shapes is governed not only by the material standard (ASTM A36) but also by a separate dimensional and tolerancing standard. The primary standard for structural shapes in the U.S. is ASTM A6 / A6M, "Standard Specification for General Requirements for Rolled Structural Steel Bars, Plates, Shapes, and Sheet Piling". This companion standard specifies the permitted variations in cross-sectional dimensions (depth, flange width, thickness), straightness, weight, and camber for all structural shapes, including H-beams, channels, and angles. Therefore, a complete specification for an A36 H-beam involves both standards: the material must meet ASTM A36 for chemistry and mechanical properties, and the physical dimensions must conform to ASTM A6/A6M.