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This specification covers standard specification for alloy steel bars, suitable for surface hardening by nitriding, designated as Classes A, B, C, and D. Class A and Class D bars are general-purpose bars; Class B bars are free-machining bars; Class C bars contain nickel and are characterized by higher core strength. All classes shall be furnished in the hot-rolled, quenched, and tempered condition. The steel shall be made by the electric-furnace process only. The microstructure resulting from heat treatment shall not show free ferrite in amounts exceeding the prescribed values. The maximum depth of total and partial decarburization of hot-rolled bars and heat-treated bars shall not exceed the amounts prescribed. Heat or cast analysis shall be performed on four classes of steel, wherein the material shall conform to the required chemical composition for carbon, manganese, phosphorus, sulfur, silicon, chromium, aluminum, molybdenum, selenium, and nickel. After quenching and tempering, the steel shall conform to one of the specified hardness ranges.