There are many types of abrasives, and the selection principle is directly related to the physical and mechanical properties of the workpiece material to be processed.
Generally speaking, when grinding workpiece materials with higher tensile strength, it is better to choose corundum abrasives with higher toughness; for grinding workpiece materials with lower tensile strength, choose silicon carbide with higher brittleness and higher hardness. Class abrasives are suitable.
When choosing abrasives, consider the chemical properties between the workpiece material and the abrasive. The chemical reaction between the abrasive and the workpiece material is the main reason for the chemical wear of the abrasive. If silicon carbide abrasives are used to grind steel, strong chemical wear will occur. There is no such reaction when grinding corundum abrasives, and no chemical wear will occur. On the contrary, corundum abrasives will produce strong chemical reactions when grinding glass, especially when water is cooled, while silicon carbide abrasives have no such reaction when grinding glass. Therefore, corundum-type abrasives can be used to grind steel workpieces, but are not suitable for grinding glass, and silicon carbide abrasives are not suitable for grinding steel.
The chemical affinity between the abrasive and the workpiece material should also be paid attention to, especially the affinity between some difficult-to-machine materials and the abrasive is obvious. For example, when silicon carbide abrasives grind heat-resistant alloys, since silicon carbide can react with iron self-chemically and under the action of high temperature in the grinding zone, silicon carbide can decompose and interact with certain metal components in the workpiece material (such as Co , Ni, Cr, W, etc.) to form compounds, which cause serious wear of silicon carbide grinding wheels, and when single crystal corundum is used to grind heat-resistant alloys, better grinding results can be achieved. In addition, when choosing an abrasive, the red hardness of the abrasive must be considered.
The following describes the performance and application range of their respective abrasives.
① Brown corundum (A) The abrasive has high toughness, high hardness and sharp particles. Therefore, it is suitable for grinding materials with high tensile strength, such as carbon steel, ordinary alloy steel, malleable cast steel, hard bronze, etc. Brown corundum is cheap and widely used, and is regarded as a general-purpose abrasive. The second grade of brown corundum can be used as abrasives for grinding wheels, emery tiles, emery cloth, sandpaper, and resin cutting wheels.
② The hardness of white corundum (WA) is slightly higher than that of brown corundum, but its toughness is lower. Hard abrasives are easy to cut into the workpiece, which can reduce the deformation of the workpiece and the heat of grinding. White corundum abrasive is suitable for fine grinding, tool sharpening, thread grinding and grinding of workpieces that are easy to deform and burn, but the price is higher than brown corundum.
③ Single crystal corundum (SA) abrasives have good multi-edge cutting edges, high hardness and toughness. This kind of abrasive is not easily broken during grinding, has strong cutting ability and long life, and is suitable for processing harder metal materials, such as high-vanadium high-speed steel, heat-resistant alloy steel and cobalt-based, nickel-based alloy steel and stainless steel. Especially high vanadium steel containing 2% to 3% vanadium has poor grindability and is difficult to grind with general abrasives, but it is suitable for single crystal corundum abrasives. Single crystal corundum abrasives can obtain good grinding results when grinding hardened steel, tool steel and other alloy steels. The production volume of single crystal corundum abrasive is relatively small, and it is only recommended for the grinding of heat-resistant alloys and hard-to-grind metal materials.
④ Microcrystalline corundum (MA) is similar to brown corundum in appearance, color and chemical composition. The difference is that its particles are composed of many tiny crystals. It has the characteristics of high strength, high toughness and good self-sharpening, and it is not easy to fall off into large particles during the grinding process. The abrasive tools made of it have little wear and are suitable for the grinding of stainless steel, carbon steel, bearing steel, special ductile iron and other materials, as well as heavy-duty grinding and precision grinding.
⑤ The hardness of chromium corundum (PA) is similar to that of white corundum, and its toughness is slightly higher than that of white corundum. It has better cutting performance and higher strength and sufficient brittleness. Therefore, the surface of the grinding workpiece is not easy to burn and cracks. Can increase productivity. Abrasives made with it have good status retention, so they are suitable for forming grinding. Chrome corundum has better grinding performance than white corundum, which can reduce the surface roughness value of the processed surface. Chromium corundum is widely used in the grinding of hardened steel, alloy steel tools, threads, and precision grinding of measuring tools and instrument parts.
⑥ Zirconium corundum (ZA) is a composite oxide of Al2O3 and ZrO2. It has good toughness and is suitable for heavy-duty grinding and grinding of heat-resistant alloy steel, titanium alloy, and austenitic stainless steel.
⑦ Black corundum (BA) The abrasive is black in appearance, has certain toughness, and has lower hardness than brown corundum. It is mostly used for free grinding, such as before electroplating, polishing or rough grinding, for sandblasting, making coarse grinding wheels, emery cloth, and sandpaper. Wait.
⑧ Black silicon carbide (C) has higher hardness than corundum abrasives, sharp cutting edge, but brittleness. Good thermal conductivity, fast heat dissipation, self-sharpening performance due to corundum abrasive. It is suitable for processing materials with low tensile strength, such as gray cast iron, white cast iron, bronze, brass, ore, refractory materials, glass, ceramics, leather, rubber, etc. It is also suitable for grinding heat-sensitive materials. Dry grinding. Black silicon carbide abrasives can be used for free grinding and are widely used in cutting and shaping operations such as jewelry, jade and agate products.
⑨ Green Silicon Carbide (GC) Abrasive properties are harder and more brittle than black silicon carbide, and have sharper cutting edges. It is easy to cut into the workpiece, but the toughness is not high. In addition to the same uses as black silicon carbide, green silicon carbide is mainly suitable for the grinding of hard alloy tools and workpieces, thread grinding and fine grinding of tools, as well as the grinding of agate, watch and gem bearings, high-end jewelry, jade, Cutting and free grinding of precious metals (such as germanium). Its price is higher than that of black silicon carbide. In addition to grinding hard alloy materials and processing some workpieces with higher technical requirements, black silicon carbide abrasives should be used as much as possible.
⑩ Cubic silicon carbide (SC) is brittle and sharp. Whetstone and small grinding wheels made of it have strong grinding ability when superfinishing and groove grinding of miniature bearings, and can reduce the surface roughness value of miniature bearings.
⑪ Boron carbide (BC) The abrasive is black, and the particles are more easily broken than diamond to form a new sharp cutting edge, with better cutting performance retention. However, due to the small scale of industrial production, the particle size of the boron carbide produced is only 100# and finer. In addition, the boron carbide abrasive has poor thermal stability and cannot withstand high temperatures, so it is often used as a grinding paste or mixed in oil. For free grinding, suitable for processing and polishing of cemented carbide, gemstones, ceramics, molds, and precision components.
