The glass micro beads

General points
"Micro beads" or "micro spheres" generally designate the abrasives or products thrown up and having a spherical shape and whose diameter is inferior to the millimetre. In particular, this is the case of the glass micro beads made of full spheres and covering granulometries ranges meeting determined calibration standards.

Manufacturing
The raw material is made of selected salvage glasses with a very precise composition. These glass fragments are crushed, purified, cleaned and dried. They are then grinded into small dimensions grains, sifted and stored according their granulometric classes before putting them in the furnace.
They are then under an angular form. Thanks to a regular feeding, the glass grains are introduced in a vertical furnace. At the base of the furnace, a series of burners gives a climbing speed to the gas which carry upwards the glass grains while giving them calories.
With a determined temperature (complete fusion), the phenomenon of surface tension makes the contact surface of the grain taut. This surface is initially angular and becomes more reduced for a same mass: the sphere (see manufacturing schema).
The glass beads obtained are then cooled down, selected and classified through successive siftings in order to form some granulometric classes adapted to the various uses of the product.

Features
Composition: high quality Sodo-Calcique glass, free from silicone and free silica, characterized by a high elastic limit.
Real density: from 2,46 to 2,49
Apparent density: 1,6
Granulometry: from 45 to 850 µ (see chart granulometries)
Hardness: 5,5 to 6 Mohs, that is to say about 45-50 Rc
Consumption: about 3% of the outflow (variable according to the part hardness and the using pressure).

Uses
The "Sodo-Calciques" are essentially used in compressed air projection machines, in dry or wet environment, according to the grains granulometry. (see chart compatibility)
They are used for industrial applications which require a precision of the surface state, a respect of the tolerances of the treated parts and the obtaining of clean metallurgic surfaces. They are used in particular for shot-peening operations on steel or light alloys and to obtain semi shiny satiny surfaces on any alloy. (see chart uses)
They are also used for the cleaning of glassworks, rubber, injection mould, ironworks dies moulds, for the renovation of mechanical parts and for the decoration.
The "Alumino-Silicates", more resistant (hardness 6 to 7 Mohs), are especially devoted to the leading edge industries such as the aeronautics or the medical industry for shot-peening operations.

The ceramic micro beads

General points
The ceramic micro beads are recent shots with new features. With their original properties, they are between the steel beads and the glass beads. They bring new possibilities in the impacts surfaces treatment area.

Manufacturing
The micro beads are made from oxides through the electro-fusion process (high temperature fusion). Their internal structure is characterized by a Zircon crystalline phase, closely overlapping in a vitreous phase of amorphous Silica (no free silica under the crystallized form).
Its very low porosity compared to the one of other ceramics gives it a perfectly smooth surface. This structure which combines a high density with a low elasticity gives rise to a very strong resistance to the impact, the wear and the fragmentation. It allows thus some treatments with high intensities.
Free from metal, these beads, comparable to the glass beads, are non-polluting.

Features
Composition: Zircon 68%, vitreous silica 32%
Real density: 3,8
Apparent density: 2,4
Granulometry: from 125 to 850 µ and more (see chart granulometries)
Hardness: 7 Mohs, that is to say about 65 Rc
Consumption: very low (variable according to the applications)

Uses
They are essentially used in compressed air projection machines, in dry or wet environment, and in blast wheel machine, according to the grains granulometry (see chart compatibility).
They are used for shot-peening applications on any support and in particular for the high levels of shot-peening. They are used everywhere they allow eliminating the decontamination operation which is essential with the use of steel beads.
They are also used for removing of rough patches and surface finishing operations, on very hard products, in particular for the treatment of stainless steels (see chart uses).

Nota:
As for the metallic abrasives, a variant of angular grains is made through a process specific to the product. It makes it possible to obtain grains with identical physical and crystallographic properties, in similar granulometry brackets. Nevertheless, its remarkable life time and its cost destines it to a use in wheels machine, everywhere one will look for an inert abrasive, not contaminating and slightly dusty.