Analysis of inclusions and carbides in mold casting billets of Cr12MoV steel
The transformation of different phases,the precipitation of inclusions and carbides in the Cr12MoV cold work die steel were calculated using Factsage thermodynamic software.The inclusions and carbides of the mold casting billets were analyzed using OM and SEM.It is shown that Cr12MoV steel is dominated by irregular rare-earth complex oxygen sulfide and sulfide inclusions,specifically Ce2S3,Ce2O2S and La2S3 inclusions.The Al2O3 and the MnS inclusions exist in the mold-cast billet in the form of rare-earth complex oxygen sulfide and sulfide inclusions after modification by rare earth elements.The density and area ratio of inclusions are 102～136 pieces/mm2 and 0.06％～0.15％,re-spectively.The equivalent diameters of inclusions are mainly in the range of 2.5～3.0 μm.Cr12MoV cold work mold steel contains a large number of carbides,in which the carbides are Fe-riched and Cr-riched eutectic carbides of M23C6 type.The average equivalent diameter of carbides in the center of bil-lets is 4.9 μm and 3.7 μm at the edge.The area proportion of carbides from the edge to the center of bil-lets ranges from 2.94％to 4.31％.
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