Main characteristics of soft abrasives. Types of soft abrasive materials.
The main characteristics of the abrasive materials are:
– The shape of the abrasive grains
– The size of the abrasive grain
– Hardness and mechanical strength of the abrasive grain
– Abrasive capabilities / utility /
– Mineral composition of abrasive grains / grain-metric composition /
The shape of the abrasive grains depends on the nature of the abrasive material and is characterized by their length, height and width. The abrasive grains are basically 4 types:
- Blocky Shape (High Bulk density)
- Sharp Shape (Low Bulk density)
- Platelet Shaped
- Extreme Shapes
The abrasive grain is characterized by the type of their surface / smooth or rough / on the shape and form of the edges and the protuberances / sharp, rounded, jagged, etc. / Grain with sharp edges much easier penetrates the material being processed. Grains which are composed of more than one material are loose in structure and are more easily destroyed in less effort.
Definition of the hardness of the abrasive material used in Mosch scale where certain materials are sorted in ascending order and any subsequent material may scratch the surface of the previous. With the increase of the temperature the stiffness of the material falls. For example, by heating the electro corundum from 20 to 1000 ° C, its microhardness falls from 19800 to 5880 MN/m.
Minerals, which are used for abrasives may have natural or artificial origin: industrial diamond, synthetic diamond, carbide / silicon carbide / cubic zirconia, Cubic boron nitride / borazon /, electrocorundum / electrocorundum is derived from melted in electric furnaces corundum /, quartz.
The group of “soft abrasive” conditionally include: Chromium (III) oxide Cr2O3, Iron Oxide, diatomaceous earth / diatomite /, Calcium Carbonate, talc and even broken brick, glass, ceramics, residues from fruit pits.
Diatomite (kieselguhr) or Diatomaceous earth
very light sedimentary rock consisting mainly of partially or completely preserved skeletons of microscopic algae – diatoms. In the best types diatomite contains more than 80% silica having different color.
also consists essentially of silica, but unlike diatomite intensively absorbs moisture.
Chromium (III) oxide Cr2O3
is used in the form of powder to prepare soft polishing pastes for processing of non-ferrous metals, steel and non-metals.
Alumina – white powder of natural origin, which is used for the preparation of pastes used for fine polishing of steel, cast iron, as well as glass and plastics.
Technical chalk / limestone
Technical chalk powder is a product that comes from natural limestone or chalk. It consists of very small particles of calcium carbonate. Available in lumps or powder and according to their chemical – physical properties differs to types A, B and C. It is used in the polishing of precious and non-ferrous metals and alloys.
Vienna Lime Chalk Powder
It is made of Calcium Carbonate with a small impurity of magnesium oxide and iron oxide. Besides polishing can also be applied to bring extra colour on stainless steel. Used for metal finishing polishing of metals mostly.