Abstract: Four different shot-peening processes were adopted for the 300M steel, and then the residual stress and its distribution, the microstructure and its distribution, and the microhardness and its distribution the surface roughness, were tested and analyzed respectively for the shot-peening layers to provide technical data for the subsequent guidance of production practice. The results show that the high hardness ceramic shot can obtain high residual compressive stress with lower shot peening strength, and the surface roughness value will not be significantly increased. Although the residual stress distribution is good after shot peening with shots cut from steel wire, the surface roughness increases greatly. Shot peening with large-diameter high-strength steel wire can not improve the compressive residual stress level, but can greatly increase the roughness value. Composite shot peening can effectively solve the contradiction between shot peening strength and roughness. On the premise that the roughness changes little, the composite shot peening process of steel wire cutting shot+ceramic shot can obtain better strengthening effect and surface structure.

Key words: shot peening, residual stress, surface roughness, microhardness