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Bearing steel skill requirements
Source: Bearing network time: 2012-12-28
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Bearing steel is generally developed in high quality, high function and various types. Bearing steel is divided into high carbon chromium bearing steel, carburized bearing steel, high temperature bearing steel, stainless bearing steel and special special. Bearing information.
In order to get used to the needs of high temperature, high speed, high load, corrosion resistance and radiation resistance; demand to develop a series of new bearing steels with special functions. In order to reduce the oxygen content of bearing steel; carry out vacuum exercise, electroslag remelting, electron beam weight The welding skills of the bearing steel such as melting. While the training of large-volume bearing steel is smelted by electric arc furnace; it is developed into various types of primary furnaces and furnaces.
At present; the bearing steel with capacity greater than 60 tons of primary furnace + LF / VD or RH + continuous casting + continuous rolling process is selected; in order to reach high quality, high power and low energy consumption. In the heat treatment process; by the bottom furnace, cover The furnace is developed into a continuous controllable atmosphere annealing furnace for heat treatment. At present, the continuous heat treatment furnace has a maximum length of 150 m; the spheroidization arrangement of the produced bearing steel is stable and uniform; the decarburization layer.
Since the 1970s; following the economic development and industrial skills advancement; the expansion of the use of bearings, and the development of international trade; has promoted the internationalization of bearing steel specifications and the development and application of new skills, new processes and new equipment; High-quality, low-cost supporting skills and process equipment came into being. Japan and Germany have built high-purity, high-quality bearing steel production lines; the steel output value is added agile; steel quality and fatigue life is large The progress of the range. The oxygen content of bearing steel produced in Japan and Sweden fell below 10ppm. In the late 1980s; Japan's Shanyang Special Steel Company's leading level was 5.4ppm; reached the level of vacuum remelted bearing steel.
The contact fatigue life of the bearing is very sensitive to the uniformity of the steel arrangement. It improves the cleanliness (reduces the impurity elements and inclusions in the steel); promotes the fine and uniform distribution of non-metallic inclusions and carbides in the steel; can improve the bearing steel The fatigue life of the touch. The arrangement of the bearing steel should be such that the fine-grained carbide particles are evenly distributed on the tempered martensite matrix; this arrangement can give the bearing steel the required function. The primary in the high-carbon bearing steel Alloying elements are carbon, chromium, silicon, manganese, vanadium, etc.
How to obtain the spheroidization arrangement is an important issue in the production of bearing steel; controlled rolling and controlled cooling is an important production process of leading bearing steel. After controlled rolling or rapid cooling after rolling, the reticulated carbide is eliminated; suitable preparation arrangements can be obtained; Bearing steel spheroidizing annealing time; refine carbide; improve fatigue life.
In these years; Russia and Japan use low temperature controlled rolling (800 Â° C ~ 850 Â° C or less); after rolling, use air cooling plus short time annealing; or completely cancel the spheroidizing annealing process; you can get qualified bearing steel arrangement. Bearing steel 650 Â°C temperature processing is also a new skill. If the eutectoid steel or high carbon steel has a fine grain arrangement before thermal processing or can form fine grains during the processing, it is within the melting temperature range of (0.4 to 0.6); At a certain strain rate; superplasticity occurs.
The US Naval Research Institute (NSP) conducted a 650 Â° C temperature processing experiment on 52100 steel; the true strain at 650 Â° C is 2.5. No cracking occurs. Therefore, it is possible to replace the high temperature processing with spheroidizing annealing at 650 Â° C. The combination of processes; this is important for simplifying equipment and processes, saving energy, and improving quality.
In terms of heat treatment; progress has been made in improving the quality of spheroidizing annealing; obtaining fine, uniform, spherical carbides and shortening the annealing time or canceling the spheroidizing annealing process; that is, the wire rod production is selected twice to arrange annealing; After the 720 Â° C ~ 730 Â° C recrystallization annealing to 760 Â° C arrangement annealing. This can get low hardness, good spheroidization, no network of carbide arrangements; the key to ensure that the central pull reduction rate â‰¥ 14%. The process improves the power of the heat treatment furnace by 25%~30%. The continuous spheroidizing annealing heat treatment skill is the development direction of the bearing steel heat treatment.
All countries are researching and developing new bearing steels; expanding and replacing traditional bearing steels, such as fast carburizing bearing steels; and modifying the chemical composition to improve the carburizing speed; the carbon content is 0.08%~0. 20% progressed to about 0. 45%; carburization time was shortened from 7 hours to 30 minutes. Developed high-frequency hardened bearing steel; used medium carbon steel or medium carbon manganese, chrome steel; replaced by high frequency heating quenching Bearing steel; both simplified the production process and reduced the cost; and improved the use of life.
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