This specification covers standards for hot-wrought, special quality microalloyed carbon steel bars intended for use in applications where as-rolled mechanical properties are desired. A typical end use includes hydraulic cylinder shafts. The typical chemical composition of microalloyed carbon steel shall contain carbon, manganese, phosphorus, sulfur, and vanadium. Heat and product analyses shall be conducted wherein the material shall conform to the required chemical composition for vanadium, columbium (niobium), and molybdenum. The elements and specified chemical ranges shall not exceed the required limits. The steel bars shall undergo tension test and conform to the mechanical property requirements such as yield strength, tensile strength, and elongation.

1.1 This specification covers hot-wrought, special quality microalloyed carbon steel bars intended for use in applications where as-rolled mechanical properties are desired. A typical end use is hydraulic cylinder shafts.

1.2 The bars shall be furnished to chemical composition and mechanical properties as provided herein. Chemical composition is based on standard carbon steel grades modified to include microalloying elements such as columbium (niobium), vanadium, or molybdenum. Three strength classes are available, designated 75 [520], 80 [550], and 100 [690], corresponding to the minimum yield strength in ksi.

1.3 Sections and sizes of bar steels available are covered in Specification A29/A29M.

1.4 Supplementary Requirements S1 to S5 are provided for use when additional controls or requirements are desired. These shall apply only when specified on the purchase order.

1.5 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.

1.6 Unless the order specifies the applicable “M” specification designation, the material shall be furnished to the inch-pound units.

1.7 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.