ASTM A573 covers structural carbon-manganese-silicon steel plate made to fine-grain practice, and it exists specifically to deliver better notch toughness than a plain structural plate at atmospheric-temperature service. It's a general structural specification rather than a pressure vessel one — think storage tanks, structural weldments, and fabricated equipment where fracture resistance at ambient and modestly cold temperatures matters more than certification for a boiler code. Fine-grain melting practice is what separates A573 from ordinary structural carbon steel: finer grain size directly improves Charpy impact performance without requiring alloy additions.

The specification defines three grades — 58, 65, and 70 — with the number again indicating minimum tensile strength in ksi. All three share the same basic carbon-manganese-silicon chemistry; the difference between grades is primarily in carbon and manganese content, with higher grades running slightly richer in both to reach higher strength. Plate thickness under A573 is capped at 1.5 in. [40 mm], reflecting its role as thinner structural plate rather than heavy pressure vessel stock. Because it isn't heat-treated, A573 machines similarly to other as-rolled or normalized carbon steel plate.

All three A573 grades machine as fine-grain, as-rolled or normalized carbon-manganese-silicon plate — there's no heat-treated hardness to contend with, and cutting forces scale gently with grade as carbon and manganese content step up from Grade 58 to Grade 70. The fine-grain melting practice that gives this steel its toughness advantage doesn't meaningfully change machinability; it affects fracture behavior at the microstructural level rather than bulk hardness or abrasiveness.

As with other hot-rolled plate, the as-rolled surface — mill scale and any decarburized skin — is the most abrasive part of the workpiece, and the first pass into that surface typically sees faster edge wear than subsequent passes into clean material below it. Chip formation is continuous-to-segmented depending on feed and geometry, consistent with other low-to-medium carbon steels in this strength range, and a standard chipbreaker geometry controls chip length without difficulty.

Because Grade 70 carries noticeably more carbon and manganese than Grade 58, expect modestly higher cutting forces and slightly faster tool wear at the top of the range; a coated carbide grade with good abrasion resistance covers the full grade spread without needing to switch tooling between grades. Rigid setups and steady chip load matter more for surface finish and tool life on this family than any special grade-specific tooling strategy.