ASTM A573 is a structural carbon-manganese-silicon steel plate specification built around one specific goal: better notch toughness than a standard structural plate like A36, without stepping up to a full low-alloy grade. It's offered in three grades — 58, 65, and 70 — named for their minimum tensile strength in ksi. The numbers in this page's designation correspond to Grade 65, which carries a specified tensile range of 65–77 ksi and a 35 ksi minimum yield. The old catalog data behind this page did not reliably confirm what the "81" in its title referred to, so that portion is not repeated here as a verified fact.

What A573 adds over a plain structural plate is a tighter, more deliberate chemistry — controlled manganese and silicon levels combined with a total aluminum addition — aimed at refining grain size and reducing the risk of brittle fracture at lower service temperatures or under impact loading. That makes it a common choice for pressure vessel shells, structural weldments, and fabricated equipment where a designer wants meaningfully better toughness margins than A36 without the cost or machining difficulty of a low-alloy or quenched-and-tempered plate. It's still a weldable, formable carbon steel at its core — the notch-toughness improvement comes from process and chemistry control, not from alloying it into a different material class.

A573 Grade 65 machines the way most carbon-manganese structural plate does — moderate hardness, predictable chip formation, and no unusual metallurgical surprises. The controlled manganese and silicon that give this grade its improved notch toughness don't meaningfully change how it responds to a cutting edge; the alloying is aimed at fracture behavior in service, not at raising hardness or abrasiveness the way a true alloy addition would. Shops that regularly cut A36 or similar structural plate will find A573 behaves very similarly at the machine.

Chip control is generally good with a standard chipbreaker geometry, and cutting forces stay moderate across the plate's practical thickness range. As with any plate product, the as-rolled surface carries mill scale that's more abrasive than the base metal underneath, so the first pass into an unmachined face tends to dull an edge faster than the numbers for the bulk material would suggest — many shops treat that initial scale-breaking pass differently from subsequent finishing passes.

A sharp edge and steady feed keep surface finish consistent and avoid the mild built-up-edge tendency that softer carbon steels can show at low cutting speeds. A general-purpose P-range carbide grade with a wear-resistant coating handles turning, facing, drilling, and edge-prep work on this plate without needing anything specialized.