Shot peening
Shot peening, also known as shot peening, is one of the effective methods to improve the fatigue life of parts. Shot peening is to spray a high-speed stream of projectiles onto the surface of the workpiece, causing the surface of the workpiece to undergo plastic deformation and form a strengthening layer of a certain thickness. A higher residual stress is formed in the strengthening layer. Due to the presence of compressive stress on the surface of the workpiece, when the workpiece is subjected to load, part of the stress resistance can be offset, thereby improving the fatigue strength of the workpiece.
Shot peening is used to remove scale, rust, molding sand and old paint film on medium-sized and large metal products and castings and forgings with a thickness of not less than 2mm or that do not require accurate size and contour. Shot peening is a cleaning method before surface coating (plating), which is widely used in large shipyards, heavy machinery plants and automobile plants.
Shot peening is a cold treatment process, which is widely used to improve metal parts that have been in high-stress service for a long time, such as compressor blades of aircraft engines, fuselage structural parts, and automobile transmission system parts.
Shot peening is a process in which countless small round media called steel shots are continuously sprayed onto the surface of a part at high speed under a completely controlled state, thereby generating a residual compressive stress layer on the surface. When each steel shot hits a metal part, it is like a miniature rod hitting the surface, knocking out small indentations or depressions. When depressions are formed, the metal surface is stretched. Under the surface, the compressed grains try to restore the surface to its original shape, resulting in a hemispherical indentation under a highly compressed force, and countless depressions are re-formed to form a uniform residual compressive stress layer. Ultimately, under the protection of the compressive stress layer, the parts have greatly improved fatigue resistance and extended service life.
Shot peening & sand blasting
Both shot peening and sand blasting use high-pressure wind or compressed air as power to blow it out at high speed and impact the surface of the workpiece to achieve a cleaning effect, but the effect is different when the medium is selected.
Shot peening has a strong impact force and a significant cleaning effect for surface treatment. However, the treatment of thin plate workpieces by shot peening can easily deform the workpiece, and the steel shot hitting the workpiece surface (regardless of shot peening or shot peening) causes the metal substrate to deform, such as Fe3O4 and Fe2O3, because they have no plasticity, they are broken and peeled off, and the oil film is deformed together with the substrate, so for workpieces with oil stains, shot peening and shot peening cannot completely remove the oil stains. Among the existing workpiece surface treatment methods, sand blasting should have the best cleaning effect.
After shot peening, the dirt on the workpiece surface is removed, the workpiece surface is not damaged, and the surface area is increased. Since the workpiece surface is not damaged during the processing, the excess energy generated during the processing will cause the surface of the workpiece substrate to be strengthened. The surface of the workpiece treated by shot peening is the original color of the metal. Since the surface is a spherical surface, part of the light is refracted, so the workpiece is matte after processing.
Sandblasting is suitable for workpieces with high requirements for surface cleaning. After sandblasting, the dirt on the workpiece surface is removed, the workpiece surface is slightly damaged, and the surface area is greatly increased, thereby increasing the bonding strength between the workpiece and the coating/plating layer. The surface of the workpiece after sandblasting is the original color of the metal, but because the surface is rough, the light is refracted, so there is no metallic luster, so the surface is dark. At present, the general sandblasting equipment in my country is mostly composed of bulky sand conveying machinery such as screw conveyors, scrapers, and bucket elevators. Users need to build a deep pit and make a waterproof layer to install the machinery. The construction cost is high, the maintenance workload and maintenance cost are large, and a large amount of silicon dioxide powder (commonly known as silica dust) is generated during the sandblasting process. It cannot be removed, which seriously affects the health of the operators and pollutes the environment.
Characteristics of shot peening
1) Metallic or non-metallic projectiles can be used arbitrarily to meet the different requirements of cleaning the workpiece surface.
2) The flexibility of cleaning is large, and it is easy to clean the inner and outer surfaces of complex workpieces and the inner wall of pipe fittings, and it is not limited by the site.The equipment can be placed near extra-large workpieces.
3) The equipment structure is relatively simple, the whole machine investment is small, there are fewer wearing parts, and the maintenance cost is low.
4) It must be equipped with a high-power air compressor station. Under the same cleaning effect, the energy consumption is large.
5) The cleaning surface is prone to moisture and rust.
6) The cleaning efficiency is low, the operator is large, and the labor intensity is high.
Shot peening cleaning process is a widely used surface strengthening process. Its equipment is simple, the cost is low, it is not limited by the shape and position of the workpiece, and it is easy to operate, but the working environment is poor. Shot peening is widely used to improve the mechanical strength of parts and wear resistance, fatigue resistance and corrosion resistance; it can also be used for surface matting, descaling and elimination of residual stress of castings, forgings and welds.
Post time: Mar-21-2025