Shot peening process for metal surfaces

　　Shot peening is a process that uses high-speed jets of strengthening steel shot to impact the surface of a workpiece, thereby improving some of its mechanical properties and altering its surface condition. Shot peening can improve the mechanical strength, wear resistance, fatigue resistance, and corrosion resistance of parts. It can also be used for surface finishing, descaling, and eliminating residual stress in castings, forgings, and weldments.

　　Shot peening is further divided into shot peening and sandblasting. Shot peening provides a powerful impact and significant cleaning effect. However, when treating thin sheet metal workpieces, shot peening can easily cause deformation. Furthermore, the impact of steel shot on the workpiece surface (whether shot blasting or shot peening) deforms the metal substrate. Since Fe3O4 and Fe2O3 lack plasticity, they break and peel off, while the oil film deforms along with the substrate. Therefore, shot blasting and shot peening cannot remove oil stains from workpieces with oil contamination. Among existing workpiece surface treatment methods, sandblasting offers the best cleaning effect.

　　Sandblasting is suitable for cleaning workpieces with high surface finish requirements. However, most commonly used sandblasting equipment in my country currently consists of primitive and cumbersome sand conveying machinery such as hinges, scrapers, and bucket elevators. Users need to construct a deep pit and waterproof layer to install the machinery, resulting in high construction costs, significant maintenance workload and costs, and the large amount of silica dust generated during sandblasting that cannot be removed, seriously affecting the health of operators and polluting the environment.

　　Shot peening is divided into general shot peening and stress shot peening. In general treatment, the steel plate is in a free state, and high-speed steel shot is used to strike the inside of the steel plate, creating pre-stress on its surface. This reduces tensile stress on the steel plate surface during operation and increases its service life.

　　Stress shot peening involves pre-bending the steel plate under a certain force before shot peening.

　　Classification of Shot Peening Equipment

　　Shot peening strengthening equipment mainly falls into two categories:

　　1. Mechanical centrifugal shot peening machine: suitable for parts requiring high shot peening intensity, with few varieties, large batches, simple shapes, and large sizes.

　　2. Pneumatic shot peening machine (compressed air type): suitable for parts requiring moderate shot peening intensity, with complex shapes, and small sizes.