Cold drawing and recovery for improved microstructural and mechanical properties of non-quenched and tempered steel fasteners

Cold deformation is an effective approach for enhancing the strength of many metallic materials. Efforts continue to be expended to improve existing processes for manufacturing non-quenched and tempered steel for industrial applications. This study investigates the treatment of non-quenched and tempered steel fasteners via cold drawing deformation and recovery treatment to achieve improved microstructural and mechanical properties. The results, which were measured using optical microscopy, scanning electron microscopy, transmission electron microscopy, tensile tests, and Charpy impact tests, demonstrated that a sample subjected to cold drawing deformation and subsequent recovery treatment exhibited increased σb, σ0.2, ε, and impact absorption energy compared to a sample subjected to cold drawing deformation alone. These enhanced properties were attributable to stable sub-grains as well as fine, uniformly dispersed precipitates which formed during recovery treatment. This study demonstrates that a combination of cold drawing deformation and recovery treatment is an effective technique for producing non-quenched and tempered steel fasteners of superior microstructural and mechanical properties.