The varieties of abrasives can be divided into natural abrasives and artificial abrasives.

Natural Abrasives

All materials in nature that can be used for grinding or grinding are collectively called natural abrasives. Common natural abrasives are as follows:
1. Diamond

(1) For dressing the grinding wheel;

(2) Grinding and grinding difficult materials (such as cemented carbide, gem glass, stone, etc.).

2. Natural corundum

(1) high quality corundum (commonly known as gemstone) sapphire (containing titanium), ruby (containing chromium), etc.;

(2) ordinary corundum, black or brownish red;

In natural corundum, the first kind is mainly used for jewelry, the second kind can be used as abrasive, used to manufacture grinding wheel, whetstone, sandpaper, emery cloth or micro powder, grinding paste, etc.

Artificial Abrasives

1, Corundum series of artificial abrasive

Artificial abrasives belonging to the corundum system include Brown Fused Alumina, White Fused Alumina, Zirconia Fused Alumina, Microcrystalline Fused Alumina, Single Crystal Fused Alumina, Pink Fused Alumina, Black Fused Alumina and bauxite sintered corundum.

(1) Brown Fused Alumina (A)

Brown Fused Alumina is bauxite, anthracite and iron filings as raw materials, in the arc furnace by high temperature smelting. In the smelting process, the carbon in anthracite will bauxite in silicon oxide (SiO2), iron oxide and titanium oxide and other impurities reduction into metal, these metals together into ferroalloy, due to its density than corundum melt and settle to the bottom of the furnace and corundum melt separation.

Brown Fused Alumina has strong crushing resistance, oxidation resistance, corrosion resistance, good chemical stability, is a widely used abrasive. It is suitable for grinding metal materials with high tensile strength, such as common carbon steel, hard bronze, alloy steel, malleable cast iron, etc.

(2) White Fused Alumina (WA)

White Fused Alumina (a - Al2o3 is an abrasive which is heated melting and recrystallization of alumina powder as raw material in electric arc furnace. The impurities in the raw materials are not eliminated in the smelting process, so the quality of White Fused Alumina is closely related to the purity of the raw materials.

The content of A12O3 in White Fused Alumina should be more than 97%, and its hardness is higher than that of brown Fused Alumina, but its brittleness is larger. It has good cutting, oxidation and gas corrosion resistance, and good insulation. It is mainly used for fine grinding and fine grinding of quenched steel and alloy steel, grinding threads and gears, etc. White Fused Alumina can also be used for precision casting and high-grade refractory materials.

(3) Monocrystalline Fused Alumina (MA)

The raw materials and smelting methods of Monocrystalline Fused Alumina are basically the same as those of BFA. Immediately after the furnace is shut down, the molten liquid is poured into the mold by means of expulsion or dumping for rapid cooling (generally within 30 min), so as to obtain the aggregate of fine crystals.

In the smelting process ofMonocrystalline Fused Alumina, the impurity reduction degree is poor, the Al2O3 content is 94% ~ 96%, the crystal size is generally 80 ~ 300 / tm, the crystal account for 57% ~ 85%, the maximum crystal size is not more than 400 ~ 600μm. It has the characteristics of high strength and toughness. Suitable for heavy load grinding, can grind stainless steel, carbon steel, bearing steel and special ductile iron and other materials, because the abrasive particles in the process of grinding micro-edge broken state, is also used in precision grinding and even mirror grinding.

(4) Single Crystal Aluminum Oxide (SA)

Single Crystal Aluminum Oxide is fused with bauxite, anthracite, iron filings and pyrite (FeS) as raw materials in the arc furnace. The iron oxide, silicon dioxide and titanium oxide in the bauxite have been reduced and composed of iron alloy settling from the molten liquid to the bottom of the furnace. A small part of alumina reacts with carbon and ferrous sulfide to generate a small amount of aluminum sulfide (Al2S3) to fill the single crystal particles. When the frit is cooled and put into water, the aluminum sulfide is dissolved, and the single crystal corundum separated by aluminum sulfide can be dispersed to become abrasive of natural size.

Single Crystal Aluminum Oxide is gray, its particle shape is the same product shape, the crystal does not contain impurities, with a multi-angular cutting edge, under the same grinding force, the torque formed is less than other abrasive, so it is not easy to break, mechanical strength is high, single particle compressive strength is 22 ~ 38 kg, and BFA only 10 ~ 20kg. Single Crystal Aluminum Oxide has high hardness and toughness, so the cutting ability is strong, can be used to process tool steel, alloy steel, stainless steel, high vanadium steel and so on.

 (5) Black fused alumina (BA)

The smelting method of black corundum is the same as that of brown corundum. It is made of trihydrate bauxite as raw material, adding a small amount of reducing agent, and smelting. Its power consumption is about two-thirds of brown corundum. Black, main chemical composition: Al203 is not less than 77%, SiO2 content is 10%-12%, Fe203 content is 7%-10%, TiO2 is about 3%, density is not less than 3.61g/cm3.

Black corundum has good self-sharpening property, less heat during grinding and good roughness of the workpiece. It is suitable for polishing the bottom surface before electroplating of parts, polishing aluminum products and stainless steel, and can also be used for polishing optical glass and wood processing. Because of its hydrophilic good, can be used in the manufacture of sandpaper, emery cloth and resin abrasives, can also be used as grinding paste and polishing powder. Black corundum is not suitable for making ceramic abrasive tools because of its high iron content.

2, Carbide series of artificial abrasive

Silicon Carbide (C, GC)

Silicon Carbide is quartz, petroleum coke as the main material, wood powder, salt as auxiliary materials according to a certain proportion of mixed into the resistance furnace, through high temperature smelting and made of artificial abrasive.

Silicon carbide is black and green: black silicon carbide is black or blue black, green silicon carbide is green or blue-green. In the manufacturing process, the production of green silicon carbide is characterized by the use of pure raw materials, adding salt to the furnace charge, it can promote the product is green. The purity of green silicon carbide is higher than that of black silicon carbide.

Silicon carbide does not react with any acid, but the melt of basic oxide can promote the decomposition of silicon carbide.

Compared with corundum artificial abrasive, black silicon carbide has higher hardness and greater brittleness. It is suitable for processing metal and non-metallic materials with low tensile strength, such as gray cast iron, brass, lead and other non-ferrous metals, as well as hard brittle materials such as ceramics and glass stone.

Green silicon carbide compared with black silicon carbide, its purity, hardness, brittleness is slightly higher, suitable for processing hard and brittle materials, such as hard alloy, glass, agate, etc., is also widely used in measuring tools, cutting tools, die fine grinding and aircraft, automobiles, ships and other engine cylinder honing