scope:

This specification covers hot-wrought, special quality, carbon steel bars and bar size shapes produced to mechanical property requirements and intended for general constructional applications.

The bars are available in nine strength grades designated 310, 345, 380, 415, 450, 485, 515, 550, and 620 [45, 50, 55, 60, 65, 70, 75, 80, and 90] corresponding to the minimum ultimate tensile strength in MPa [ksi]. The chemical composition is selected by the manufacturer to develop the required mechanical properties.

Hot-wrought, special quality, carbon steel bars subject to mechanical property requirements are hot wrought in straight lengths only. Sections and sizes available are covered in ASTM A 29/A 29M.

Some applications may require one or more of the available designations shown under Supplementary Requirements.

Note 1-Merchant quality, hot-wrought carbon steel bars subject to mechanical property requirements are covered in M 227M/M 227.

This specification is applicable to orders in either SI units (as M 255M) or inch-pound units (as M 255). SI units and inch-pound units are not necessarily equivalent. Inch-pound units are shown in brackets in the text for clarity, but they are the applicable values when the material is ordered to M 255.