Effect of Rare Earth Ce on Primary Carbides in GCr15 Bearing Steel
With therapid development of high-end equipment manufacturing industry in China,the demand and research of high-quality bearing steel is increasingly urgent.Currently,GCr15 bearing steel is one of the most widely used high-carbon chromium bearing steels,the influence of primary carbides on bearing steel and control of primary carbides become more and more important with the continuous improvement of the cleanliness for bearing steel.Therefore,by adding rare earth Ce to GCr15 bearing steel,the effect of rare earth Ce on primary carbides in bearing steel was studied in this work.Thermo-Calc software was applied to thermodynamically analyze the precipitation behavior of primary carbides during solidification of GCr15 bearing steel.XRD,OLS5100 Laser Scanning Confocal Microscope and SEM-EDS were used to analyze the composition and microstructure of primary carbides in GCr15 bearing steel.The results showed that the typical primary carbides in GCr15 bearing steel were M3C,M7C3 and M3C2.The quantity and size of primary carbides could be obviously reduced with reasonable addition of rare earth Ce in GCr15 bearing steel.Especially when the content of rare earth Ce was 320×10-6,the area ratio and maximum size of primary carbides was reduced by 3.22％and 16.21 pm respectively.Moreover,with the increasing addition of rare earth Ce in GCr15 bearing steel,the nucleation core of primary carbides changed from MnS and Al2O3 to Ce-O-S with smaller size,which led to the refinement of primary carbides.
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