Microstructure Deformation And Void Evolution During Hot Radial Ring Rolling Of As-cast GCr15 Bearing Ring-blank

Small-medium size bearing rings are the main components of small-medium size bearings, which have been widely used in all kinds of mechanical machinery and equipment. Comparing to the conventional ring rolling technology, hot radial ring rolling of as-cast ring blank is proposed as a new solution based on casting-ring rolling technique especially for small-medium size bearing rings manufacturing. This new technique is created to short the manufacturing process by using as-cast ring blank instead of as-forge ring blank, obtained from steps including upsetting, piercing and levelling. It would bring huge economic and environmental benefits. However, this new technology could not gain its popularization and application presently, for it is still in its infancy-lack of corresponding theories and actual production experience. Consequently, my work focused on some fundamental aspects in this field. The key problems such as improving microstructure and diminishing casting flaws of the as-cast blank are taken into consideration carefully, providing scientific guidance for further application and research for this new technique.Firstly, aimed at improving microstructure, the microstructure evolution behaviors of hot radial ring rolling of as-cast GCr15 steel are revealed using a FE modelling approach. The grain size evolution and dynamic recrystallization evolution rules are concentrated. What should be emphasized is that the grain size refinement limit has been firstly found and special attention is paid into it from the aspect of strain and Z-H parameter. This find would offers significant guidance for refining the as-cast ring blank grains to the same extent compare to the as-forge ring blank. What’s more, the effects of rolling parameters on the grain refinement are studied aimed at obtaining high quality rings. The hot radial ring rolling of as-cast GCr15 steel experiments and corresponding microstructure tests have been carried out. The results would bring guidance for grain size control in this new process.Secondly, aimed at diminishing casting flaws, spherical voids are defined in the as-cast ring blank as representatives to study voids evolution behaviors using a FE modelling approach. The basic evolution rules of voids and effects of rolling parameters on voids evolution are discussed based on local coordinate established especially for the spherical void. What should be emphasized is that the spherical void shape prediction model is defined by connecting the voids deformation pattern and related ring material deformation pattern based on assumptions from comparing void evolution principles of spherical and cylindrical voids. The void evolution experiment has been designed and conducted. The void evolution rules during hot radial ring rolling have been reveled further using an experiment approach.