Shot peening process is a widely used surface treatment method to improve fatigue strength and wear resistance. The surface of the material is subjected to a so-called "hammering effect", which causes great local deformation to form a work-hardened layer, or compressive residual stress. The effect of shot peening on the fatigue strength of high toughness spring steel was studied in this paper. In the experiment, a conventional shot peening machine was used to evaluate the optimal conditions with uniform size metal pellets.
The spraying method of the shot blasting material is centrifugal spray type, and the shot blasting with a diameter of 1.0mm is high carbon cast iron, and the workpiece used is commercial spring steel JIS-SUP10. The effect of shot peening time on surface characteristics and fatigue strength was studied. Fatigue experiments were carried out on a plane-bending machine, and S-N curves were established for both unshot and shot peened samples.
The main results are as follows: the surface of the workpiece has been fully deformed after shot peening. Residual stress is generated near the surface of all shot peened workpieces. With the increase of shot peening time, the area with residual stress expands to depth direction. The maximum compressive residual stress value is about 950MPa. In the process of a large number of repeated bending to fracture, shot peening treatment can effectively improve the fatigue strength. When the shot peening speed is 60ms-1 and the shot peening treatment is 90s, the fatigue strength obtained is about 525MPa. This peening time is almost equivalent to the full coverage time. This experiment found that the optimization time of conventional shot peening treatment was 90s.
