Cr12MoV steel is the most widely used cold work die steel,which belongs to high chromium and high car-bon lesteritic steel,and the form,quantity,size and distribution of carbides in the steel have an important impact on the properties of Cr12MoV steel.Metallographic microscope,scanning electron microscope,three-dimensional cor-rosion engraving device for inclusions,X-ray diffractometer and energy dispersive analyzer were used to analyze the type,morphology and distribution of carbides in Cr12MoV die casting billets in a factory,and the phase transition and carbide precipitation behavior of Cr12MoV cold work die steel were calculated by Thermo-Calc 2020b.The re-sults show that the carbide types of Cr12MoV cold work die steel are chromium-rich and iron-rich M7C3 carbides and M23C6 carbides,the main elements of M7C3 carbides are chromium,iron,carbon and molybdenum,and the main el-ements of M23C6 carbides are iron,chromium,molybdenum and carbon.The carbide morphology in the casting bil-let can be mainly divided into four categories,granular carbide,bulky carbide,rod-like carbide,and reticulated car-bide.The size of granular carbide is 2-5 μm,the size of bulk carbide is 10-15 μm,the size of rod carbide is 30-40μm,and the reticulated carbide is formed by the aggregation of granular,bulky and rod-like carbides and its size is up to 80 μm.The evolution of carbide morphology from edge to core is as follows,granular → blocky→ rod-like reticulated,the heterogeneity of carbide from edge to core is gradually enhanced,and the carbide at the edge is dis-tributed in a granular manner,the carbides at 1/4 are long rod-shaped,and the carbides in core are segregated into a network.From edge to core,the average equivalent diameter of carbide increases from 5.7 μm at the edge to 8.5 μm at the core,the proportion of carbide area increases from 8.2％to 9.5％from the core,and the density of carbide decreases from 2 961/mm2 at the edge to 1 189/mm2 at the core.By analyzing the type,morphology and distribution of carbides in Cr12MoV steel billets,the distribution law of carbides in the casting billets is found,which provides a theoretical basis for the factory to regulate the carbide morphology in the steel and optimize the performance of steel.
Cr12MoVcold work die steeldie casting billetcarbidethree-dimensional engraving
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