| A chromium vanadium steel is characterized for use in a hex wrench hand tool application. The application justifies the need for a high strength and ductile steel. The standard steel alloy used for hex wrenches is 8650. An alternative lower cost steel alloy, 61B60CrV, is considered for the hex wrench hand tool application. The microstructure achieved is tempered martensite. First martensite is formed to create a high strength but brittle material. Then the martensite is reheated and tempered to improve the ductility of the material. Both 8650 and 61B60CrV alloys are thermally processed in the same way to create the tempered martensitic structure. The mechanical properties of the proposed steel is evaluated and compared to that of the standard 8650 steel alloy. The 61B60CrV alloy evaluation includes torsion testing, hardness and hardenability measurements, and grain size determination. The 61B60CrV alloy is proven to meet the hex wrench hand tool mechanical requirements with a tempered martensitic microstructure. During Jominy hardness testing of the 61B60CrV alloy, it is determined that the hardness requirements are met for a wide range of microstructures. Samples of the 61B60CrV alloy are austempered for different durations then quenched to room temperature to create samples with different amounts of mixed microstructures of bainite and martensite. A range of mixed microstructures are shown to meet the strength, ductility, and hardness requirements for the hex wrench hand tool application without tempering. |
