Enhanced Axial Tension-tension Fatigue Resistance of a 51CrV4 Spring Steel by Cryogenic Treatment

51CrV4 spring steel is widely used in heavy duty dump trucks ascribing to its superior mechanical properties. The fatigue life and strength of dump trucks are the main performance indicators that must be considered in the manufacturing process. Cryogenic treatment (CT) can improve the main performance of materials which has been proved by recently research. The effect of cryogenic treatment CT on the axial tensile fatigue strength of 51CrV4 spring steel was studied in this paper. The results showed that the axial tension-tension fatigue life of 51CrV4 spring steel after CT was significantly higher than conventional heat treatment (CHT) samples. The microstructure of 51CrV4 leaf spring material is mainly acicular bainite and thin strip martensite after CT. Compared with CHT, CT makes the microstructure of the material more compact. The introduction of cryogenic treatment (CT) before tempering makes the Ca element in the material aggregate, and the micro amount of Ca has the function of deoxidizing and desulphurizing and improving the morphology of sulfide, thus enhancing the fatigue life of the material.