Analysis of microstructures,inclusions and carbides of G95Cr18 bearing steel billets by mold casting
Based on Thermo-calc software,the matrix structure,phase transformation and carbides pre-cipitation of G95Cr18 bearing steel were analyzed.Metallographic microscope and scanning electron microscope were used to analyze the mold casting billets structures,inclusions and carbides.The re-search shows that the main components of inclusions in the casting slab of G95Cr18 bearing steel are Ce,O,Al,Ca and a few other elements.The main type of inclusions is rare earth oxygen sulfide Ce-Al-O-Ca-S,and a small amount of magnesia-aluminum spinel Al-Mg-O is also found.The inclusion dens-ity is 31-48 mm2,and the average sizes of inclusions are concentrated in a range of 2.2 μm to 2.6 μm with the inclusion area proportion of 0.02％to 0.03％.The area proportion of carbides from the edge to the core increases from 3.0％to 7.5％,and the morphology of carbides shows a transforming trend of block → rod → strip → network.Most of the network carbides near the core are distributed along the grain boundaries.These types of carbides are composed of bright white Nb-enriched MC carbides and gray M7C3 carbides enriched in Cr,respectively.The sizes of MC carbides are smaller than that of M7C3 carbides,and they present as massive carbides in the matrix and network carbides in the grain boundary.
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