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Bearing raw materials: new technologies and the direction of bearing steel
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| Time：2016.08.30 News Sources：Shandong Xinkaite bearing Co.,Ltd. Views：
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Bearing steel is mainly used in the manufacture of rotary body and the rotary bearing ring. Since the bearing should have a long life, high-precision, low heat, high speed, high rigidity, low noise, high wear resistance and other characteristics, thus requiring bearing steel should have: high hardness, uniform hardness, high elastic limit, high contact fatigue strength and toughness necessary, certain hardenability, in the atmosphere of the lubricant in the corrosion resistance. To achieve the above performance requirements, bearing steel chemical composition uniformity, non-metallic inclusion content and type, size and distribution of carbides, decarburization demanding. Bearing steel to the development of high quality, high performance and multi-species direction as a whole. Bearing steel according to characteristics and application environments are divided into: carbon chromium bearing steel, carburizing bearing steel, high temperature bearing steel, stainless steel and special bearing special bearing materials.
To meet the high-temperature, high-speed, high load, corrosion, anti-radiation requirements, the need to develop a series of new bearing steel with special properties. In order to reduce the oxygen content of bearing steel, the development of vacuum smelting, remelting, electron beam remelting bearing steel smelting technology. The bulk of bearing steel smelting by the arc melting, develop into various types of foreign First Canadian refining furnace. Currently, the use of early capacity greater than 60 tons furnace + LF / VD or RH + + continuous casting and rolling bearing steel production process, in order to achieve high-quality, high efficiency, low energy consumption purposes. In terms of the heat treatment process by car bottom furnace, bell furnace developed into a continuous annealing furnace controlled atmosphere heat treatment. Currently, continuous heat treatment furnace up to 150m, processing bearing steel ball of the organization stable and uniform, decarburization is small, low energy consumption.
Since the 1970s, with economic development and industrial technology, to expand the scope of application of the bearing; and the development of international trade, but also to promote the development and application of international standards of bearing steel and new technologies, new processes and new equipment, efficiency , high quality, low cost of supporting technology and process equipment came into being. Japan and Germany etc. built a high purity, high-quality bearing steel production line, steel production increased rapidly, the quality of life and fatigue steel substantial progress. Japan and Sweden, the oxygen content of bearing steel production down to 10ppm or less. The late 1980s, Japans Sanyo Special Steel Companys advanced level of 5.4ppm, reached the level of vacuum remelting bearing steel.
The contact fatigue life of the bearing on the uniformity of the steel structure is very sensitive. Progress cleanliness (reduce impurity elements and inclusion content in steel), to promote non-metallic inclusions in steel and carbide fine and uniform distribution of the contact can improve fatigue life of bearing steel. Tissue bearing steel using state should be evenly distributed fine carbide particles tempered martensitic matrix, such organizations can give the required performance of the bearing steel. Carbon bearing steel in the main alloying elements carbon, chromium, silicon, manganese and vanadium.
How to get the ball bearing steel production organization is an important topic, controlled rolling and cooling is important advanced bearing steel production process. By rapid cooling after controlled rolling or rolling eliminate network carbide to obtain suitable tissue preparation, ball bearings can be shortened annealing time, refining carbide, progressive fatigue life. In recent years, Russia and Japan controlled rolling and low temperature (800 ℃ ~ 850 ℃ or less), plus air cooling after rolling a short anneal, or completely cancel spheroidizing, you can get qualified bearing steel structure. Bearing steel 650 ℃ temperature processing is also new technology. Before eutectoid steel or high carbon steel having a thermal processing if the fine grain, or during processing to form fine grains, then (0.4 to 0.6) the melting temperature in the range, at a certain strain rate, exhibit superplasticity. Naval Postgraduate School (NSP) for 52100 steel processing temperature of 650 ℃ tests showed that at 650 ℃ 2.5 true strain fracture does not occur. Therefore, it is possible to 650 ℃ temperature and high-temperature processing instead of processing combined with the ball annealing process, which simplifies the equipment and processes, save energy, improve quality is important.
In terms of heat treatment, advances in ball annealing quality, access to small, uniform, spherical carbides and shortening the annealing time or cancel ball annealing step of research progress has been made, namely wire rod produced using organized two annealing, the drawing after 720 ℃ ~ 730 ℃ to 760 ℃ annealing recrystallization annealing organization.
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