Shot blast cleaning method of aluminum casting surface

1、Characteristics of shot blasting cleaning process:

After shot blast cleaning of aluminum die castings, the following effects can be achieved.

  • High efficiency: The shot wheel can finish cleaning in a few minutes with the shot quantity of 110-260 kg / min and the shot velocity of 50-75 m / s. For large batch or large size workpieces, multiple shot blasters can be used for shot blasting at the same time.
  • It can clean, color and polish the surface of parts. After shot blasting, the adherent, thin edge, flying wing and spot on the surface of the workpiece can be removed, and the scratch can be eliminated, so that the workpiece presents the basic color.
  • Eliminate surface stress concentration. During the cooling process of parts, due to the uneven wall thickness and the inconsistent cooling speed, the surface stress concentration occurs. After shot blasting, the surface structure can be improved, the surface stress concentration can be eliminated, the fatigue strength can be increased, and the surface hardness can be slightly improved.
  • Increase the surface beauty. Because the projectile is spherical, small concave holes are produced when it is shot on the workpiece, which is spherical, like concave mirror. Under the light, it is pleasant to see if stars are twinkling.
  • Improve the surface spraying adhesion. After shot blasting, the surface roughness can reach RA 1.6-6.3 μ m, the surface area is greatly increased, and the surface dirt is eliminated at the same time. Therefore, the adhesion of surface painting or other coatings is greatly enhanced

2、Difference of shot blasting equipment between aluminum alloy parts and ferrous metal parts

The shot blasting equipment used for aluminum alloy parts and ferrous metal parts is basically the same in structure, and its working principle tends to be the same. However, due to the small size and light weight of aluminum alloy parts, the small particle size of shot used in cleaning, the aluminum powder produced is easy to explode and other characteristics, it is also different from the shot blasting equipment used in ferrous metal parts as follows.

  • The bearing capacity of the workpiece bearing device does not need to be very large. Because under the same volume, the weight of aluminum alloy parts is only about 1 / 3 of that of steel parts.
  • The filter air speed of separator shall be reduced. Due to the use of φ 0.2-φ 0.6 m m projectiles, the wind speed is too high and easy to be sucked away. Usually, the wind speed is 2-3 M / S (when cleaning ferrous metal parts, the wind speed of separator is generally 4-5 M / s). At the same time, the coordinate position of the separation plate vertex also changes correspondingly, that is, the adjustable plate on the separation plate is changed.
  • The projectile speed has changed. Due to the low hardness of aluminum alloy parts, in order to meet the specified surface roughness requirements, under the condition of the given particle size and material of the projectile, the projectile speed needs to be determined by experiments. But it is often lower than the shot blasting speed of ferrous metal parts.
  • The dedusting system shall be equipped with explosion-proof device. Aluminum alloy parts produce aluminum powder during shot blasting, and aluminum powder is conductive, flammable and explosive dust, which should be specially treated.

3、Characteristics of shot blasting equipment for aluminum alloy parts

Because the shape, size, weight and surface cleaning requirements of aluminum alloy parts are different, the selected shot blasting equipment is also different.

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