Cr12MoV钢铸坯碳化物解析

Analysis of carbide in Cr12MoV steel billet

Cr12MoV钢是应用最广泛的冷作模具钢,属于高铬高碳莱氏体钢,钢中碳化物的形态、数量、大小和分布对Cr12MoV钢的性能有重要影响。采用金相显微镜、扫描电镜、夹杂物三维腐刻装置、X射线衍射仪和能谱分析仪对某厂生产的Cr12MoV模铸坯中碳化物类型、形态及分布情况进行解析,使用Thermo-Calc 2020b计算Cr12MoV冷作模具钢的相转变和碳化物析出行为。结果表明,Cr12MoV冷作模具钢碳化物类型为富铬富铁的M7C3型碳化物和M23C6型碳化物,M7C3型碳化物所含主要元素为铬、铁、碳、钼,M23C6型碳化物所含主要元素为铁、铬、钼、碳。铸坯中碳化物形貌主要可以分为4类,颗粒状碳化物、块状碳化物、棒状碳化物、网状碳化物。颗粒状碳化物尺寸为2~5μm,块状碳化物尺寸为10~15μm,棒状碳化物尺寸为30~40μm,网状碳化物由颗粒状、块状、棒状碳化物聚集形成,其尺寸达80μm。从边部到芯部碳化物形态的演变规律为颗粒状→块状→棒状→网状,边部到芯部碳化物不均匀性逐渐增强,边部碳化物呈颗粒状弥散分布,1/4处碳化物呈长棒状,芯部碳化物偏聚成网状;铸坯从边部到芯部,碳化物的平均等效直径由边部的5.7μm增加到芯部的8.5μm,碳化物面积比例由边部的8.2%增长到芯部的9.5%,碳化物的密度由边部的2 961个/mm^(2)下降到芯部的1 189个/mm^(2)。通过解析Cr12MoV钢铸坯中碳化物的类型、形态与分布,寻找碳化物在铸坯中的分布规律,为工厂调控钢中碳化物形态、优化钢的性能提供理论依据。

Cr12MoV steel is the most widely used cold work die steel,which belongs to high chromium and high carbon 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 corrosion 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 results 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 elements of M23C6 carbides are iron,chromium,molybdenum and carbon.The carbide morphology in the casting billet can be mainly divided into four categories,granular carbide,bulky carbide,rod-like carbide,and reticulated carbide.The size of granular carbide is 2-5μm,the size of bulk carbide is 10-15μm,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 80μm.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 distributed 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 5.7μm at the edge to 8.5μm 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 2961/mm^(2) at the edge to 1189/mm^(2) 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.