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Grinding wheel, also known as consolidation abrasive, is a kind of consolidation abrasive with certain strength, which is consolidated into a certain shape (mostly round, with a through hole in the center) by bond. It is generally composed of abrasives, binders and pores, which are often called the three elements of consolidated abrasives. According to the different classification of bond, there are ceramic (bond) wheel, resin (bond) wheel and rubber (bond) wheel. Grinding wheel is one of the most widely used grinding tools with the largest consumption. When used, it can rotate at high speed, and can carry out rough grinding, semi finish grinding, finish grinding, slotting and cutting on the outer circle, inner circle, plane and various profiles of metal or non-metal workpieces.
Grinding wheel is one of the most important grinding tools in grinding. Grinding wheel is a kind of porous body made by pressing, drying and baking with bond in abrasive. Due to the different abrasive, bond and manufacturing process, the characteristics of grinding wheel are very different, so it has an important impact on the grinding quality, productivity and economy. The characteristics of grinding wheel are mainly determined by abrasive, grain size, bond, hardness, structure, shape and size.
There are many kinds of grinding wheels. According to the abrasives used, they can be divided into ordinary abrasives (corundum, silicon carbide, etc.), natural abrasives, superhard abrasives and (diamond, cubic boron nitride, etc.); according to the shape, they can be divided into flat grinding wheel, beveled edge grinding wheel, cylindrical grinding wheel, cup grinding wheel, dish grinding wheel, etc.; according to the bond, they can be divided into ceramic grinding wheel, resin grinding wheel, rubber grinding wheel, metal grinding wheel, etc. The main characteristic parameters of grinding wheel are abrasive, particle size, hardness, bond, shape, size, etc. As the grinding wheel usually works at high speed, the rotation test (to ensure that the grinding wheel will not break at working speed) and static balance test (to prevent vibration of the machine tool during operation) should be carried out before use. After working for a period of time, the grinding wheel should be trimmed to restore the grinding performance and correct geometry.
Abrasive is the main raw material of grinding wheel, which is responsible for cutting work. Therefore, the abrasive must be sharp, with high hardness, good heat resistance and certain toughness.
The structure of grinding wheel refers to the volume proportion of abrasive grain, bond and air hole. It is usually graded according to the percentage of abrasive particles in the volume of grinding wheel. The grinding wheel has three kinds of organization states: compact, medium and loose, which are subdivided into 0-14, totally 15 grades. The smaller the organization number is, the larger the proportion of abrasive grains is, and the more compact the grinding wheel is; on the contrary, the larger the organization number is, the smaller the proportion of abrasive grains is, and the more loose the grinding wheel is.
The grinding wheel is fragile, so it must be handled with care to prevent cracking and damage. 2. The grinding wheel should be stored on the shelf or in the box to prevent moisture. 3. The resin bonded grinding wheel should not be in contact with alkali substances. After storage for more than one year, it must pass the rotary strength test, and the qualified one can be used.
Abrasives are tools for grinding, grinding and polishing. Most of the abrasives are artificial abrasives made of abrasives and binders, as well as natural abrasives directly processed from natural minerals 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, plastic, rubber and wood.
The abrasive tissue can be roughly divided into three types: tight, medium and loose. Each type can be further subdivided and distinguished by organization number. The larger the abrasive organization number is, the smaller the volume percentage of abrasive in the abrasive is, and the wider the gap between abrasive grains is, which means the looser the organization is. On the contrary, the smaller the organization number, the tighter the organization. The abrasive tools with loose structure are not easy to passivate in use, and have less heat in the grinding process, which can reduce the heat deformation and burn of the workpiece. The abrasive grains with tight structure are not easy to fall off, which is conducive to maintaining the geometric shape of the abrasive tools. The structure of abrasives is only controlled according to the formula of abrasives during manufacturing, and is generally not measured. Consolidated abrasive tools are mainly composed of diamond, cubic boron nitride and bond. Due to the high price and good wear resistance of diamond and cubic boron nitride, the bonded abrasives made of them are different from those made of ordinary abrasives. In addition to the superhard abrasive layer, there are also transition layer and substrate. The superhard abrasive layer is a part of cutting, which is composed of superhard abrasive and bond. The matrix plays a supporting role in grinding, which is composed of metal, bakelite or ceramics. The transition layer is used to connect the substrate and the super hard abrasive layer, which is composed of bond and sometimes can be omitted. Commonly used binders are resin, metal, electroplating metal and ceramics. The manufacturing process of consolidated Abrasives includes: batching, mixing, forming, heat treatment, processing and inspection, etc. With different binders, the manufacturing process is not the same. The ceramic bonded abrasives mainly adopt the pressing method. After weighing the abrasives and the bond according to the weight ratio of the formula, they are put into the mixer to mix evenly, put into the metal mold, and form the rough abrasives on the press. The blank is dried and then roasted in the kiln. The firing temperature is about 1300 ℃. When low melting point sintering binder is used, the sintering temperature is lower than 1000 ℃. Then according to the size and shape of the precise processing, and finally check the product. Resin bonded abrasives are generally formed on press at room temperature, and hot pressing process of heating and pressing is also adopted. After forming, it is hardened in the hardening furnace. When phenolic resin is used as binder, the hardening temperature is 180 ~ 200 ℃. Rubber bonded abrasives are mainly mixed by a pair of roller machines, rolled into thin sheets, and then punched with a punching knife; some loose materials are put into metal molds for forming on internal presses. After molding, it is vulcanized in the vulcanizing tank at 165 ~ 180 ℃. There are two manufacturing processes of metal bonded abrasives, powder metallurgy and electroplating, which are mainly used for super hard abrasive bonded abrasives. In powder metallurgy process, bronze and other materials are used as binders. After mixing, hot pressing or pressure forming at room temperature is adopted, and then sintering is carried out. In the electroplating method, nickel or nickel cobalt alloy is used as electroplating metal, and the abrasives are consolidated on the substrate according to the electroplating process to make abrasives. Special kinds of abrasives include sintered corundum abrasives and fiber abrasives. Sintered corundum abrasives are made by mixing and molding alumina powder and appropriate amount of chromium oxide, and sintering at about 1800 ℃. This kind of abrasives has compact structure and high strength. It is mainly used for processing clocks, meters and other parts. Fiber abrasives are made of fibers (such as nylon) with or adhered to abrasives as raw materials. It has good elasticity and is mainly used for polishing metal materials and their products.
In the process of using abrasives, when the abrasives are blunt, the abrasives will fall off partially or completely from the abrasives due to the partial fragmentation of the abrasives or the fracture of the bond, and the abrasives on the working face of the abrasives will constantly appear new cutting edges or expose new sharp abrasives, so that the Abrasives can maintain the cutting performance in a certain period of time. This kind of self sharpening of abrasive tools is a prominent feature compared with general cutting tools. As early as the Neolithic age, human beings began to use natural grindstones to process stone knives, stone axes, bone implements, angle implements, dental implements and other tools. In the 19th century, ceramic grinding wheels made of natural abrasives and clay appeared in the United States. Around 1900, man-made Abrasives came out, and various abrasives made of man-made Abrasives came into being one after another, which created a good foundation for the rapid development of grinding and grinding machines Conditions. Since then, the proportion of natural abrasives in abrasives has gradually decreased.
According to the source of raw materials, abrasives can be divided into natural abrasives and artificial abrasives. The natural abrasive tools commonly used in machinery industry are oilstone. According to the basic shape and structural characteristics, artificial abrasives can be divided into five categories: grinding wheel, grinding head, Whetstone, sand tile and so on. In addition, abrasives are also traditionally listed as a kind of abrasives.
According to the different abrasives used, consolidated Abrasives can be divided into ordinary abrasives and super hard abrasives. The former is made of common 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.
Ordinary abrasive consolidation abrasive is a kind of abrasive which is consolidated into a certain shape and has a certain strength by bond. Generally by abrasive, bond and pore composition, these three parts are often called the three elements of consolidated abrasive.
Abrasive plays a cutting role in abrasive tools. Bond is the loose abrasive consolidation into abrasive materials, there are inorganic and organic two types. Inorganic binders include ceramics, magnesite and sodium silicate, and organic binders include resin, rubber and shellac. The most commonly used are ceramic, resin and rubber bond.
During grinding, the air hole can hold and discharge the chips, and can hold the coolant, which is helpful to the heat dissipation. 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, also known as the fourth element of abrasive.
The characteristics of common abrasive bonded abrasives include: shape, size, particle size, hardness, microstructure and bond. Abrasive hardness refers to the difficulty of abrasive particles falling off from the surface of abrasive tools under the action of external force. It reflects the strength of abrasive particles held by binder.
Abrasive size
Particle size refers to the size of abrasive particles, which is represented by particle size number.
The national standard specifies two particle sizes of abrasive and micro powder.
Particle size refers to the size of abrasive particles. The particle size can be divided into abrasive and micro powder. The abrasive with the particle size of 40 μ m is called abrasive. The particle size is expressed by the number of holes per inch of the length of the screen through which the abrasive particles pass. For example, the abrasive size of 60 # means that it can just pass through the screen with 60 holes per inch. The abrasive with particle size less than 40 μ m is called micro powder. The particle size is represented by W and the number after W, and the value after w represents the actual size of the powder.