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Effect Of Shot Peening Treatment On Fatigue Strength Of High Toughness Spring Steel

The shot peening process is a widely used surface treatment method used to improve fatigue strength and wear resistance. The surface of the material obtains a so-called "hammering effect" that greatly deforms locally to form a hardened layer, or to initiate a compressive residual stress. In this paper, the effect of shot peening treatment on the fatigue strength of high toughness spring steel was studied. In the experiment, the optimized conditions were evaluated using a conventional shot peening machine with a uniform size of the metal pellets. Shot blasting method is a centrifugal jet type, the diameter of 1.0mm shot peening is a high-carbon cast iron, the use of the workpiece is the commodity spring steel JIS-SUP10. The effects of shot peening time on surface properties and fatigue strength were studied preliminarily. The fatigue test was carried out on a flat-bending tester, and the S-N curve was established for the non-shot peening and shot peening samples.

The main results are as follows: the surface of the workpiece after shot peening has been fully deformed. Residual stresses are created near the surface of all shot peened parts. As the shot peening time increases, the area with residual stress expands in the depth direction. The maximum compressive residual stress is about 950 MPa. Pilling hardening can effectively increase the fatigue strength during a large number of cycles of bending until breaking. When the shot peening speed of 60m s-1, shot peening 90s, the fatigue strength of about 525MPa. This shot time is almost equal to the full coverage time. In this experiment, the optimization time of conventional shot peening was 90s.