What is Shot Blasting?
Shot blasting is a mechanical surface treatment process. In the investment casting process, Shot blasting is a post-production finishing service. It is processed by the rapid impact on the surface of investment castings with an abrasive material. Its purpose is to remove various impurities from different surfaces. It is a faster and more efficient process when compared to filing for flash removal that remained on investment castings.
Shot blasting is a cold treatment process. It can be divided into shot blasting and shot peening. Shot blasting is to remove the surface oxide and other impurities to improve the appearance quality and shot blasting makes the surface of the workpiece reach a certain degree of roughness. Make the workpiece beautiful, or change the welding tensile stress of the workpiece to compressive stress and improve the service life of the workpiece.
Shot blasting is using the centrifugal force of the impeller on the throwing head of the shot blasting machine at high speed. Then to shoot the abrasive at a very high linear velocity on the surface of the treated steel to produce a striking and grinding action to remove the oxide scale on the steel surface and rust.
This process produces a certain roughness. But Shot blasting is highly efficient and can be carried out in a sealed environment.
Shot peening is the use of high-speed moving projectiles (60-110m/s) to continuously impact the surface of the strengthened workpiece, forcing the surface and surface layer (0.10-0.85mm) to undergo the following changes during cyclic deformation:
- Microscopy The microstructure is modified.
- Non-uniform plastic deformation The outer surface layer introduces residual compressive stress. The inner surface layer produces residual tensile stress.
- The outer surface roughness changes (Ra Rz).
- 1.Improve the fatigue fracture resistance of materials/parts, prevent fatigue failure, plastic deformation and brittle fracture, and improve fatigue life.
- 2.Used for removing burrs, scale and rust that may interfere with the integrity, appearance or definition of investment castings.
- 3. Prepare the surface of investment castings for coating by removing surface contaminants
- 4.Provide a surface profile for increased coating adhesion.
- 5.Induce compressive stresses on a part’s surface for increased fatigue life, increasing strength or preventing fretting of castings.
- 6.Shot blasting after heat treatment is performed to remove any oxidation or scale that has formed on the casting during prior heat treating processes.
The final result of the shot blasting surface depends on several factors: mass of the abrasive particle, particle velocity, the impactor angle of the particle, the particle shape, density, and coverage of the strokes kg/m2.
The thickness of the abrasive, the pressure of the compressed air (ie, the linear velocity of the projectile), and the time of the shot blast
- 1. According to the purpose of the casting, the specified descaling level can be cleaned. A uniform finished surface can be obtained;
- 2. Closed operation, no dust;
- 3. Applicable to steel plates above 5mm, wide flat steel and section steel;
- 4. Fast speed, high work efficiency, and stable quality.
Common shot blasting materials include steel shot, aluminum shot, ceramic micro powder, steel sand, walnut sand, corn cob, glass beads, resin sand, plastic sand, and so on.
The automotive industry, metal-manufacturing industry, foundry, aviation industry, shipbuilding, production of various welded structures, and so on.
Shot blasting is highly efficient and can be carried out in a sealed environment. With a vacuuming device and automatic painting, it is an efficient automated assembly line operation.
During heat treating of investment castings, oxidation can form during annealing, normalizing, hardening, or tempering operations depending on the particular process parameters. Shot blasting treatments easily remove this surface oxidation, which makes additional operations like machining easier to perform. It is also used for prior preparation of surfaces prior to further processing, such as welding, coloring, etc.
Shot blasting is the necessary posting treatment method after investment casting. Equipped with numerous shot blasting machines in-house, we can do this kind of service directly in our investment casting foundry.