Abrasives are an important factor in the grinding action of abrasives. The choice of abrasives is mainly determined by the properties of the workpiece materials, such as hardness, tensile strength, toughness, etc. The basic principle of selecting abrasives is to grind workpiece materials with high hardness. When the workpiece material with high tensile strength should be selected, the abrasive with high toughness should be selected; when the material with low tensile strength is used, the silicon carbide abrasive with high brittleness or high strength should be selected.
Specifically, brown corundum is suitable for grinding carbon steel, cast iron alloy steel, hard bronze, etc.; white corundum is suitable for grinding hardened steel, alloy steel, high speed steel, tool steel, etc.; black silicon carbide is suitable for grinding non-ferrous metals, rubber, leather, Plastics, etc.; Green silicon carbide is suitable for grinding hard alloys, optical glass, ceramic materials, etc.; SG, CBN ceramic abrasives are widely used in difficult-to-wear materials.
In addition, in order to give full play to the advantages of various abrasives in grinding, mixed abrasives have been widely used in the manufacture of abrasive tools to improve the grinding efficiency of abrasives. For example, when grinding ductile iron, A/WA mixed abrasive is generally used; brown and white corundum two kinds of mixed abrasives have the characteristics of high toughness of brown corundum during grinding, and also play a role in white corundum with certain brittleness and thermal conductivity. specialty. (For example, grinding crankshaft grinding wheel adopts brown and white mixing, particle size 60#～80#, hardness is soft 2 to medium 1) (rough grinding cobalt-based alloy gear toothed grinding wheel, which can be mixed with single crystal and microcrystalline) High-speed steel grinding wheel, which is made of brown corundum and green silicon carbide.) Grinding spherical bearing inner inner ring grinding wheel should be brown or white mixed. The specification is: GZ/GB80# P600×36×305 is rough grinding track. GZ/ GB80#P600×510×355.6 is the final grinding outer diameter and so on.
Abrasive size selection principle?
When selecting the abrasive grain size, it should be selected mainly according to the requirements of processing precision, surface roughness and grinding efficiency. The general principles are as follows:
It is required that the workpiece to be ground has a high roughness , and the coarse grain size should be selected; the surface roughness is required to be low , and the fine particle size should be selected.
When the workpiece requires high geometric accuracy and low surface roughness, the mixing particle size should be selected.
The geometric accuracy of the workpiece is high. When the contact area between the grinding wheel and the workpiece is small, the fine particle size should be selected. When the contact area is large, the coarse grain size is selected.
The workpiece material is hard and brittle, and the fine grain size should be selected; the workpiece material is soft and tough, and the coarse grain size should be selected.
The workpiece has poor thermal conductivity, is prone to heat deformation, and is prone to burn. The coarser grain size should be selected.
Abrasives hardness selection principle?
When selecting the hardness of the grinding tool, it is mainly selected according to the nature of the workpiece material and the grinding method. The hardness of the grinding wheel refers to the difficulty of the abrasive grains on the surface of the grinding wheel falling off under the action of grinding force. The hardness of the grinding wheel is soft, which means that the abrasive grains of the grinding wheel are easy to fall off, and the hardness of the grinding wheel is hard, indicating that the abrasive grains are difficult to fall off. The hardness of the grinding wheel and the hardness of the abrasive are two different concepts. The same kind of abrasive can be made into grinding wheels of different hardness, which is mainly determined by the performance and quantity of the bonding agent and the manufacturing process of the grinding wheel. The significant difference between grinding and cutting is that the grinding wheel has “self-sharpnessâ€. Choosing the hardness of the grinding wheel is actually choosing the self-sharpness of the grinding wheel. It is hoped that the sharp grinding particles should not fall off too early, and should not be blunt or fall off. . The general principles are as follows:
When grinding hard materials, the abrasive particles are easy to blunt, in order to make the blunt abrasive particles fall off in time, a softer abrasive tool should be selected.
When grinding soft materials, the abrasive grains are not easy to be blunt, in order not to cause the unblunt particles to fall off prematurely, a harder abrasive tool should be selected.
When grinding very soft and tough non-ferrous materials (such as aluminum and copper), in order to avoid blockage of the grinding tools, softer abrasive tools should be used.
The grinding wheel has a low line speed, and a harder grinding wheel should be used; the grinding wheel has a high line speed, and a softer grinding wheel should be used. The contact area between the grinding wheel and the workpiece is large, and a softer grinding wheel should be used; if the contact area is small, a hard grinding wheel should be used.
When grinding workpieces with poor thermal conductivity, deformation, and burns, a softer grinding wheel should be used.
In the case of dry grinding, in order to reduce the heat generation and avoid burns of the workpiece, the hardness of the grinding tool should be 1:1 softer than that of the wet grinding.
When the grinding efficiency is high , a softer grinding wheel can be selected.
When lower roughness, optional hard grindstone.
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