Abstract
Considerable efforts have been made over the last decades to improve performance of spring steels, which would increase the service time of springs and also allow vehicles weight reduction. There are different possibilities of improving properties of spring steels, from modifying the chemical composition of steels to optimizing the deformation process and changing the heat treatment parameters. Another way of improving steel properties is through refining the microstructure and reducing amount of inclusions. Therefore, the focus of the current investigation was to determine the effect of more uniform and cleaner microstructure obtained through electro-slag remelting (ESR) of steel on the mechanical and dynamic properties of spring steel, with special focus on the resistance to fatigue crack propagation. Effect of the microstructure refinement was evaluated in terms of tensile strength, elongation, fracture and impact toughness, and fatigue resistance under bending and tensile loading. After the mechanical tests the fracture surfaces of samples were analyzed using scanning electron microscope (SEM) and the influence of microstructure properties on the crack propagation and crack propagation resistance was studied. Investigation was performed on hot rolled, soft annealed and vacuum heat treated 51CrV4 spring steel produced by conventional continuous casting and compared with steel additional refined through ESR. Results shows that elimination of segregations and microstructure refinement using additional ESR process gives some improvement in terms of better repeatability and reduced scattering, but on the other hand it has negative effect on crack propagation resistance and fatigue properties of the spring steel.
Highlights
I ncreasing demands of industry, especial automotive industry on performance improvement of steels put a lot of pressure on the steel and steel parts producers
On one hand electro-slag remelting (ESR) resulted in refined microstructure of spring steel, but on the other hand ESR caused the appearance of some Al2O3 inclusions [27], otherwise absent in conventional continuous cast spring steel (CCC) specimens
It contributes to considerable increase in impact toughness, especially at sub-zero temperatures, while increase in hardness, tensile strength and fracture toughness is less pronounced
Summary
I ncreasing demands of industry, especial automotive industry on performance improvement of steels put a lot of pressure on the steel and steel parts producers. Spring steel; Crack propagation; Electro-slag remelting; Segregations; Fracture toughness. In the case of tool steels microstructure refinement and properties improvement can be achieved through utilization of electro-slag remelting (ESR) [21].
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