Articles

Abrasive grains

Abrasive materials are divided into natural and artificial. Today, the modern abrasives industry primarily uses synthetic grains to produce abrasive tools: artificial fused alumina, zirconia fused alumina, silicon carbide, and ceramic alumina. Compared to natural minerals, synthetic grains offer distinct advantages: consistent hardness and toughness, guaranteed uniformity and consistent material properties, both within a single batch and across batches. All this allows for the production of cutting abrasive tools with predictable, stable properties, which is crucial for solving industrial problems.

Abrasive grain is generally understood to be abrasive particles in the form of monocrystals, polycrystals, or fragments thereof, as well as various types of minerals used to make grinding tools. The abrasive process essentially involves "scratching" (removing a very thin layer of material) the surface being treated with multiple abrasive grains. The productivity and quality of the grinding process depend significantly on the type and correct selection of abrasive grain.
Abrasive grain is responsible for material removal; to choose the right grain, it is important to consider two properties:

• Strength (toughness)
• Hardness

There are four main types of grain used in abrasives:

• Silicon carbide is used for processing wood, stone, glass, plastic, paint, and non-ferrous metals.
• Electrocorundum – used for processing steel, non-ferrous metals, wood, and leather.
• Zirconium fused alumina is used for processing stainless steel, high-strength steel, and heat-resistant alloys.
• Ceramic electrocorundum is used for processing alloy steel and stainless steel, heat-resistant alloys.

Corn	Hardness/strength	Structure
Silicon carbide	Very hard/ the least durable	Crystalline
Electrocorundum	Solid/durable	Crystalline, uneven (with defects)
Zirconium fused alumina	Solid, very durable	Crystalline, uniform
Ceramic electrocorundum	Solid, very durable	Microcrystalline

Microcrystalline structure

The term "microcrystal" refers to the specific structure of an abrasive grain. Each individual ceramic grain consists of numerous small particles that form a single grain. Because the fine boundaries between individual particles within the ceramic grain crystal are preserved, it acquires a so-called microcrystalline structure. By manipulating the grain structure, one can vary its characteristics and impart the desired properties to the abrasive grain. This structure allows one to control the overall strength of the entire ceramic grain crystal, as the grain will always fracture along the boundaries of its constituent microcrystals.

Due to this structure, ceramic grains have a self-sharpening effect: when the tip of a grain becomes dull during use, the microcrystal is shed from the grain under increasing pressure. Since shedding occurs throughout the entire grain structure, the sharp end is constantly renewed without losing its aggressiveness.

Optimal wear of abrasives with a microcrystalline grain structure requires high contact pressure during the grinding process. The primary application for self-sharpening abrasive belts is the machining of difficult-to-machine materials, such as heat-resistant alloys, alloy steels, and stainless steels.