This specification covers a nitriding grade of premium aircraft-quality, low-alloy steel in the form of bars, forgings, mechanical tubing, and forging stock. These products have been used typically for nitrided parts such as bearings, operating under heavy loads and high speeds at moderate temperatures, and subject to very rigid inspection standards, and requiring highest surface hardness, high core toughness, and less distortion than parts made from steel requiring quenching to case harden, but usage is not limited to such applications