Microstructure refinement and its effect on properties of spring steel

Over the last decades considerable efforts have been made to develop high performance spring steels, which would allow vehicles weight reduction. One way of improving steel properties is by refining its microstructure and reducing the amount of inclusions. Therefore, the aim of the current investigation was to determine the effect of cleaner and more uniform microstructure obtained through electro-slag remelting (ESR) on the mechanical and dynamic properties of spring steel. Investigation was performed on hot rolled, soft annealed and vacuum heat treated 51CrV4 spring steel produced by conventional continuous casting and refined through ESR. Effect of microstructure refinement was evaluated in terms of tensile strength, elongation, fracture and impact toughness, and fatigue resistance under bending and tensile loading. Results show that although ESR gives some improvement, especially in terms of better repeatability and reduced scattering, it has a negative effect on the fatigue properties of spring steel.