Wyniki 1-1 spośród 1 dla zapytania: authorDesc:"JULITA DWORECKA"

Nanocrystalline structures obtained by isothermal treatment in bearing steels

  Steel is the most widely used of all metallic construction materials. It results from high strength parameters and stiffness of steel combined with its relatively low price. Increase in demands for construction materials caused by economic factors and the objective to improve competitiveness of products are now the driving force behind the research and development projects concerning steel. The projects aim at developing novel, nonstandard technologies that would allow to obtain unconventional microstructures in order to improve and optimize properties of steel. A particularly promising direction of these projects is related to obtaining nanocrystalline structure in steel. Such a microstructure provides high strength parameters and simultaneously high plasticity and crack resistance in comparison to conventional alloys of similar strength [1, 2]. Therefore, steel with nanocrystalline structure belongs to the most perspective materials to be used in the industry. At present, numerous studies on developing a novel generation of steel are in progress worldwide, with the aim of obtaining nanocrystalline structures by a bainitic transformation. In order to obtain microstructure of nanocrystalline bainite it is necessary to introduce certain specific alloying agents to steel and to carry out a precise heat treatment that would ensure a bainitic transformation. Nanocrystalline bainite could be obtained in specially designed steel grades that have the following basic chemical composition (wt %): 0.6÷1.1% C, 0.5÷2% Si, 0.3÷1.8% Mn, up to 3% Ni, up to 0.5% Mo, 0.5÷1.5% Cr, and up to 0.2% V [3]. Within the scope of this study it was an attempt to obtain bainitic nanostructure in two commercial grades of bearing steel: 100CrMnSi6-4 and 67SiMnCr6-6-4. Moreover, mechanical properties of these steels after the bainitic transformation were tested. EXPERIMENTAL STUDY Adequate content of carbon, silicon and manganese is essential for obtainin[...]

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