Form:

This specification covers a premium aircraft-quality, low-alloy steel in the form of bars, forgings, mechanical tubing, and forging stock.

Application:

Primarily for parts, such as bearing components, for service up to 500°F (260°C) and requiring a through-hardening steel capable of developing hardness not lower than 60 HRC in cross-sections 3 inches (76 mm) and under.