Hot-rolling is the definitive and universal production method for A36 structural shapes like H-beams. The process involves shaping steel at temperatures above 1700°F (925°C), which is above its recrystallization temperature. This process fundamentally defines the beam's characteristics:
Grain Structure & Properties: The high-temperature working refines the steel's grain structure, resulting in a uniform, relatively stress-free condition with good toughness and ductility. The mechanical properties are achieved directly from this controlled rolling and subsequent air cooling.
Surface Condition: The process creates a blue-gray oxide layer called mill scale. While providing some temporary protection, this scale must often be removed by blasting or grinding prior to painting or welding for optimal results.
Dimensional Capability & Tolerances: Hot-rolling is the only practical method to produce the large cross-sections and long lengths of structural H-beams. Dimensional tolerances are governed by ASTM A6 and are looser than for cold-finished products but are perfectly suitable for structural erection.
Economy: It is a highly efficient, continuous process, making A36 H-beams a cost-effective structural solution.
In essence, the "as-rolled" condition specified for A36 H-beams is a direct outcome of the hot-rolling process, balancing performance, size capability, and economy.