Bearing using the ideal information - — Silicon nitride ceramics

As machinery manufacturing industry in the direction of high precision, high speed, bearing application scope is more and more wide, the request on the performance of the bearing is becoming more and more high, especially in some special working environment, the metal bearing fails to comply with the demand, so that a complete will not work. And ceramic materials because of the advantages of small density, high elastic modulus and linear shrinkage coefficient, wear resistance, high temperature resistant, corrosion resistance and other excellent performance, become the ideal material of high speed manufacturing precision bearings. One, the characteristics and advantages of silicon nitride ceramics is in silicon nitride ceramic industry is not the most hard, toughness is not the highest, but the request of high performance bearing applications, silicon nitride is thought to have a the best comprehensive mechanical and physical properties. Look at the below, silicon nitride compared with the other bearing materials of good place. 5 kinds of bearing material performance comparison of heat resistance of ordinary steel bearing using temperature above 120 ℃, the hardness will reduce, rolling life will land. The silicon nitride has good temperature characteristic, especially suitable for high temperature environment. Centripetal force density of silicon nitride is about 3. 24 x 103 kg/m3, and the density of bearing steel is about 7. 8 x 103 kg/m3, is only about 40% of the bearing steel density, so when using roller bearings, bearing can suppress when rotating at high speed due to centrifugal force effect the increase of rolling element load. Line contraction coefficient of the linear contractive modulus of silicon nitride is about 1/4 of bearing steel, so the size of the change with temperature variation is small, so beneficial to use in the environment of the temperature change is big. Hardness, modulus of elasticity and poisson's ratio due to the elastic coefficient of silicon nitride is about 1 of bearing steel. Five times, so the relative load the elastic deformation of small, relatively high rigidity of the payload. Corrosion resistance, nonmagnetic, insulation and chemical machinery and equipment, food, Marine departments use machine, using steel bearing, its corrosion is a problem. In strong magnetic environment, using steel bearing, powder from bearing wear down oneself by adsorption between the roller and the rolling surface, this will be a bearing early spalling damage and increase the main reason of noise. Second, the preparation of silicon nitride ceramic bearings silicon nitride ceramic bearing preparation process of silicon nitride ceramic powder making bearing parts with silicon nitride powder request has the following important features: high purity; High average and fine particles; A high content of alpha. Most agree with this request to the preparation of silicon nitride powder for thermal recovery of carbon nitride method, the reaction type is: 3 - sio2 + 6 c + 2 n2 = Si3N4 + co, this kind of method to get little powder containing metal impurity, high purity, fine grain, high content of alpha, agree with the request of the bearing parts material. Silicon nitride ceramic bearing related parts molding silicon nitride ceramic bearing preparation method of a lot of related parts, such as reaction sintering method,, pressureless sintering, hot-pressing sintering, the secondary reaction sintering process. In order to get a complete dense silicon nitride material, hot isostatic pressing method is used to compare ideal. Silicon nitride ceramic bearing related parts machining of silicon nitride ceramic bearings related parts similar to bearing steel parts processing, grinding mechanism of the same at all. But because of all the properties of silicon nitride and the performance of the steel have bigger difference, so the coefficient of grinding tools in mechanical machining, machining, grinding mixture and so on all have considerable differences, the process of abrasive particle size, variety, shape, number, strength, broken characteristics and wear characteristics request are different. Currently using abrasive are mainly silicon carbide, boron carbide and diamond powder, etc. Silicon nitride ceramic bearing assembly of ordinary rolling bearing is composed of four main parts, namely the outer ring, inner ring, rolling body and frame. Because there are as many as ten kinds of rolling bearing, the persistence of the different types of bearing adopts frame way each are not identical, thus bearing assembly way also is not the same. Silicon nitride ceramic bearing as an important mechanical foundation, because of its excellent cannot compare with other bearing feature, data in the new world. In recent years, in the aerospace, Marine, nuclear industry, petroleum, chemical industry, textile industry, machinery, metallurgy, electric power, food, locomotive, subway, high speed machine tools and scientific research and national defense military technology such as category requirements at high temperature, high speed, low temperature, flammable, explosive, corrosive, vacuum, electrical insulation, non-magnetic, dry friction under special conditions, such as silicon nitride ceramic bearing is not short of substitution effect is gradually known by people.