Popular science knowledge of abrasives
Abrasives are tools used for grinding, grinding and polishing. Most of the abrasives are artificial abrasives made of abrasives and binders, and also directly processed from ores and rocks. In addition to being widely used in machinery manufacturing and other metal processing industries, abrasives are also used in grain processing, paper industry and processing of non-metallic materials such as ceramics, glass, stone, plastics, rubber and wood.
In the process of using abrasive tools, when the abrasive grains are blunt, the abrasive grains will fall off partially or completely from the abrasive tools due to the partial fragmentation of the abrasive particles themselves or the fracture of the binders, and new cutting edges or sharp abrasive grains will appear continuously on the working surface of the abrasives, so that the cutting performance of the abrasives can be maintained in a certain period of time. The self sharpening of abrasive tools is a prominent feature of abrasive tools compared with general cutting tools.
As early as the Neolithic age, human beings have begun to use grindstones to process tools such as stone knives, stone axes, bone tools, horn tools and tooth tools. In 1872, ceramic grinding wheels fired with abrasive and clay appeared in the United States. Around 1900, artificial abrasives came out, and various kinds of abrasives made by artificial abrasives were produced one after another, creating conditions for the rapid development of grinding and grinding machines. Since then, the proportion of abrasives in abrasives has gradually decreased.
According to the source of raw materials, there are two types of abrasives: Abrasives and artificial abrasives. Only whetstone is commonly used in machinery industry. According to the basic shape and structural characteristics, artificial abrasives can be divided into five categories: grinding wheel, grinding head, oilstone, sand tile (collectively referred to as consolidated abrasive tools) and coated abrasives. In addition, it is customary to list Abrasives as a class of abrasives.
According to the different abrasives used, consolidated Abrasives can be divided into ordinary abrasive consolidated abrasives and superhard consolidated abrasives. The former is made of ordinary abrasives such as corundum and silicon carbide, while the latter is made of superhard abrasives such as diamond and cubic boron nitride. In addition, there are some special varieties, such as sintered corundum abrasives.
The ordinary abrasive consolidation abrasive tool is a kind of abrasive tool which is consolidated into a certain shape and has a certain strength by the bond. It is generally composed of abrasives, binders and pores, which are often called the three elements of consolidated abrasives.
Abrasives play a cutting role in abrasives. Binders are the materials that solidify the loose Abrasives into abrasives. They are inorganic and organic. Inorganic binders include ceramics, magnesite and sodium silicate; organic binders include resin, rubber and shellac. Ceramic, resin and rubber binders are commonly used.
During grinding, the pores can hold and remove the debris, and can hold the coolant, which is helpful to the heat dissipation of grinding. In order to meet some special processing requirements, some fillers, such as sulfur and paraffin, can be impregnated into the pores to improve the performance of abrasive tools. This filler is also known as the fourth element of abrasives.
The items representing the characteristics of ordinary abrasive bonded abrasive tools are: shape, size, abrasive, particle size, hardness, microstructure and binder. The hardness of abrasive tools refers to the difficulty of abrasive particles falling off from the surface of abrasive tools under the action of external force, which reflects the strength of abrasive grains controlled by binder.
The hardness of abrasives mainly depends on the amount of binder added and the density of abrasives. If the abrasive grains are easy to fall off, the hardness of abrasives is low; otherwise, it means that the hardness is high. The hardness grades are generally divided into seven grades: super soft, soft, medium soft, medium hard, medium hard and super hard, and several small grades can be subdivided from these grades. The commonly used methods for measuring the hardness of abrasive tools are hand cone method, mechanical cone method, Rockwell hardness tester method and sandblasting hardness tester method.
Abrasives play a cutting role in abrasives. Binders are the materials that solidify the loose Abrasives into abrasives. They are inorganic and organic. Inorganic binders include ceramics, magnesite and sodium silicate; organic binders include resin, rubber and shellac. Ceramic, resin and rubber binders are commonly used.
During grinding, the pores can hold and remove the debris, and can hold the coolant, which is helpful to the heat dissipation of grinding. In order to meet some special processing requirements, some fillers, such as sulfur and paraffin, can be impregnated into the pores to improve the performance of abrasive tools. This filler is also known as the fourth element of abrasives.
The items representing the characteristics of ordinary abrasive bonded abrasive tools are: shape, size, abrasive, particle size, hardness, microstructure and binder. The hardness of abrasive tools refers to the difficulty of abrasive particles falling off from the surface of abrasive tools under the action of external force, which reflects the strength of abrasive grains controlled by binder.
The hardness of abrasives mainly depends on the amount of binder added and the density of abrasives. If the abrasive grains are easy to fall off, the hardness of abrasives is low; otherwise, it means that the hardness is high. The hardness grades are generally divided into seven grades: super soft, soft, medium soft, medium hard, medium hard and super hard, and several small grades can be subdivided from these grades. The commonly used methods for measuring the hardness of abrasive tools are hand cone method, mechanical cone method, Rockwell hardness tester method and sandblasting hardness tester method.
