| A method was proposed to obtain nano-bainite in high-carbon bearing steel. Themicrostructure and properties of the nanostructure bainite also have been investigated.With the potential use of bearing, the property of wear was also tested.Firstly, the samples of A, B, C, D and E were under the convetional heat treatment.The results indicated that the microstructure of bainite was obtained after the holding timeof1h. The fraction of bainite increased with the holding time increasing. Besides, thefraction of residual austenite decreased as the holding time increased. The Steel of F,Gand H were designed on the basis of A, B, C, D and E.On the basis of hardness and microstructure, the steel of H was the best among thesteel of F,G and H. The dynamic curves of TTT were obtianed. The samples of H steelwere under a series of heat treatments. Considering the standard of bearings, thecomprehensive properties of H austempered at225℃for6h after austenitized at860℃for1h are prior to other heat treatments.Carburized steel is the conventional material of bearing rings. To achieve thestandard of bearing rings, firstly the steel is carburized. The heat treatment is complicated.The hardness of high carbon steel on the one half of a thick bearing ring can satisfy thedemand. The high carbon bearing steel can be a potential subtitute of carburized steel. Itnot only save the cost but also simplify the heat treatment.The application of low-temperature bainitic microstructure for bearing steels has notbeen reported. The study is presented of the microstructures and mechanical properties ofbainitic bearing steel subjected to isothermal transformation at200℃for2,6,12and72hafter austenitized at950℃for40min, and air quenched. With the excellent strength andwear resistance of low-temperature bainite, this low-temperature austempering technologycould be a potential substitute of the traditional quenching and tempering heat treatment inthe manufacture of bearings. |
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