AB SHOT TECNICS , SL, is placed at Cervello, Barcelona, Spain. Our facilities have a warehousing space over 2,000 m2 for storage and distribution of all kinds of abrasives.
We have all the necessary documentation to comply with all European legislations. In the same way, we have all the safety & technical data sheets and analysis certificates from each item delivered.
There is a wide variety of abrasives that can perfectly replace the use of sand.
There are natural ones, which are extracted directly from nature, and synthetic ones, obtained through chemical or physical processes.
Aluminium oxide: its shape is angular, which gives it a high abrasion index. Suitable for a wide range of applications such as deoxidizing, pickling and surface preparation, where it’s necessary to increase the surface roughness of the metal part, such as surface preparation for painting or coating with synthetic resin or rubber, cleaning and deburring welds and cleaning paint and lacquer layers.
Glass microspheres: their shape is spherical, non-porous and, due to the rounded shape of these particles, the abrasion rate is low. Suitable for a wide variety of applications, they are especially recommended for cleaning and polishing small metal parts and for treating aluminium and stainless steel parts.
Aluminium Silicate: has similar characteristics to corundum; the grains of this material are irregularly shaped, angular, slightly laminated and varied, with slightly sharp edges. The particle acts by friction and sliding which, together with its slightly cutting edges, exerts a shearing action, with low abrasion. Its granulometry is very tight and controlled, and it has the advantage of performing a homogeneous and delicate action on the surfaces to be treated. It is suitable for removing paints and eliminating rust on metal surfaces, mainly iron.
Other available abrasives are: vegetal abrasive, vegetal shots, ceramic abrasive, ceramic shots, steel shots, plastic abrasive, plastic shots, etc.
FACTORS FOR A CORRECT FINISH.
It is just as important to achieve the desired surface finish as it’s to strike a balance between the cost and effectiveness of abrasive blasting treatment. There are several factors related to the abrasive that, together with the blasting equipment to be used, determine the final finish:
- A) SIZE:
The size of the particles will determine the roughness obtained. If we fix the pressure and the air flow, by varying the size of the grain we will vary the roughness achieved by the impact of the abrasive particle on the surface. In other words, the larger the particle size, the greater the imprint it leaves on the sandblasted material. Abrasive manufacturers use various nomenclatures and numbers to define the size of each grain, but they usually follow the FEPA regulations that set the size standards.
- B) SHAPE:
Abrasives have two typical morphologies, spherical and angular.
As a general rule, a spherical abrasive wears less the blasting equipment, the surface finish is softer to the touch (since the surface roughness does not have peaks, but has a “wave” shape due to the impact of the spheres) and the blasting process is usually slower.
In contrast, an angular abrasive wears down the blasting equipment much more, the surface finish is rough to the touch (as the surface roughness is “saw-like” due to the impact of the spherical abrasive) and the process is usually faster, as it is much more aggressive than with a spherical abrasive.
In summary, we can say that the angular abrasive works better when it comes to removing or stripping paint and corrosion layers; while the spherical abrasive, on the other hand, is better for smaller thicknesses and fine, satin finishes and shot peening processes to eliminate surface tensions in the parts.
- C) DENSITY:
Density is the weight of the abrasive by volume. This is the least determining characteristic to be taken into account when performing a blasting or shot peening job, unless the difference in density between the chosen abrasives is very wide.
The denser the material, the more energy it will have to impact the surface. In other words, one abrasive that is heavier than another can leave a deeper mark than another abrasive that is much lighter.
- D) HARDNESS:
The hardness of the abrasive will determine its effect on the surface to be sandblasted or shot-blasted.
If the abrasive is harder than the surface of the material to be sandblasted, the surface to be treated will be stripped (or deformed), as the abrasive is more resistant than the material against which it impacts.
On the contrary, if the abrasive is softer or softer than the surface of the material to be blasted, the abrasive will only remove the coating on top of the surface of the material (paint, rust, etc.) as the abrasive is less resistant than the material against which it is impacted and bounces, after such impact, without leaving a superficial mark.
Therefore, an excessive hardness of the abrasive to be blasted in relation to the hardness of the surface to be treated, can cause deformations in the workpiece and even premature wear in the blasting equipment.
The hardness of the abrasive is measured according to the Mohs scale, with the value 1 on the scale being as soft as talc, and the value 10 being as hard as diamond. If we classify the abrasives from higher to lower hardness, we see that the white corundum and the brown corundum have a hardness of 9 Mohs, followed by the ceramic shot with about 7 Mohs, the glass beads about 6 Mosh, the same as the aluminium silicate, and then come the vegetable abrasive and the plastic shot with about 3 Mohs.
Steel and stainless steel shot is normally measured in Rockwell (HRC). Steel shot differs in being low (46-51 HRC), medium (53-57 HRC) and high hardness (>64 HRC). Stainless steel shot has a hardness at origin of 30 HRC and, as it is used, reaches a hardness in operation of 45 HRC. There are also stainless steel shots up to 63-65 HRC hardness.