New technology and development direction of the ho

New technology and development direction of bearing steel (I)

bearing steel is mainly used to manufacture rolling elements and rings of rolling bearings

since the bearing should have the characteristics of long life, high precision, low calorific value, high speed, high rigidity, low noise, high wear resistance, etc., the bearing steel is required to have: high hardness, uniform hardness, high elastic limit, high contact fatigue strength, necessary toughness, certain hardenability, corrosion resistance in atmospheric lubricants. In order to meet the above performance requirements, the uniformity of chemical composition, the content and type of non-metallic inclusions, the particle size and distribution of carbides, decarburization and other requirements of bearing steel are strict

bearing steel is generally developing towards high quality, high performance and multiple varieties. Bearing steel is divided into high carbon chromium bearing steel, carburized bearing steel, high temperature bearing steel, stainless bearing steel and special bearing materials according to its characteristics and application environment

in order to meet the requirements of high temperature, high speed, high load, corrosion resistance and radiation resistance, it is necessary to develop a series of new bearing steels with special properties. In order to reduce the oxygen content of bearing steel, the smelting technologies of bearing steel such as vacuum smelting, electroslag remelting and electron beam remelting have been developed. The smelting of large quantities of bearing steel has developed from electric arc furnace smelting to various types of primary smelting furnaces plus external refining

at present, bearing steel is produced by primary smelting furnace with a capacity of more than 60 tons + LF/VD or Rh + continuous casting + continuous rolling process to achieve the purpose of high quality, high efficiency and low energy consumption. In terms of heat treatment process, the car bottom furnace and bell type furnace have been developed into continuous controllable atmosphere annealing furnace for heat treatment. At present, the longest continuous heat treatment furnace is 150m. The spheroidized structure of bearing steel processed and produced is stable and uniform, with small decarburization layer and low energy consumption

since the 1970s, with economic development and industrial technological progress, the scope of application of bearings has expanded; The development of international trade has also promoted the internationalization of bearing steel standards and the development and application of new technologies, new processes and new equipment. Supporting technologies and process equipment with high efficiency, high quality and low cost came into being. Japan and Germany have built high-purity and high-quality bearing steel production lines, which has rapidly increased the output of steel and greatly improved the quality and fatigue life of steel. The oxygen content of bearing steel produced in Japan and Sweden decreased to less than 10ppm. In the late 1980s, the advanced level of yamayo special steel company in Japan was 5.4ppm, which reached the level of vacuum remelted bearing steel

the contact fatigue life of bearing is very sensitive to the uniformity of steel structure. Improving cleanliness (reducing the content of impurity elements and inclusions in steel) and promoting the fine and uniform distribution of non-metallic inclusions and carbides in steel can improve the contact fatigue life of bearing steel. The structure of bearing steel in use should be that fine carbonation is evenly distributed on the tempered martensite matrix, and some work is low-quality simple repeated labor particles. Such structure can give the bearing steel the required properties. The main alloy elements in high carbon bearing steel are carbon, chromium, silicon, manganese, vanadium, etc

how to obtain spheroidized structure is an important problem in the production of bearing steel, and controlled rolling and controlled cooling is an important production process of advanced bearing steel. The spheroidizing annealing time of bearing steel can be shortened, the carbides can be refined and the fatigue life can be improved by controlling rolling or rapid cooling after rolling

in recent years, Russia and Japan have adopted low-temperature controlled rolling (below 800 ℃ ~850 ℃) and air cooling after rolling to improve the safety and reliability of cable products. Qualified bearing steel structure can be obtained by adding short-time annealing or completely canceling the spheroidizing annealing process. 650 ℃ warm processing of bearing steel is also a new technology. If eutectoid steel or high carbon steel has fine grain structure before hot processing or can form fine grains during processing, it will show superplasticity at a certain strain rate in the range of (0.4~0.6) melting temperature. The 650 ℃ warm working test of 52100 steel carried out by the US Naval Research Institute (NSP) shows that the true strain of 2.5 does not fracture at 650 ℃. Therefore, it is possible to replace high-temperature processing with 650 ℃ temperature processing and combine it with spheroidizing annealing process, which is important to simplify equipment and process 3 The exposed sliding parts, gears, pulleys, etc. of the experimental machine should be protected It is of great significance to save energy and improve quality