Ce对M2高速钢夹杂物和碳化物的影响

Effect of Ce on inclusions and carbides in M2 high-speed steel

  • 摘要: 国内某钢厂生产了两炉不同稀土(Ce)含量的M2高速钢,通过光学显微镜、扫描电子显微镜、X射线衍射分析以及高温共聚焦显微镜等手段,探究Ce对M2高速钢夹杂物和碳化物的影响。添加Ce后,电渣锭中S含量降低,夹杂物由大尺寸、不规则状的Al2O3改性为小尺寸、类球状的CeAlO3,夹杂物实现了完全变质。同时夹杂物数量密度减小,平均尺寸降低,热力学计算表明,电渣锭中最可能生成CeAlO3夹杂物,这与试验结果一致。电渣锭铸态组织中共晶碳化物明显细化,错配度计算表明:(001)CeAlO3与(100)γ-Fe之间的错配度为4.49%,CeAlO3可作为γ-Fe的异质形核核心,促进钢液凝固过程中形核位点的增加,大大减小共晶碳化物的生长空间。Ce的添加并未改变盘条碳化物的类型,盘条纵截面碳化物统计结果表明:添加Ce后,相同面积(1000μm2)碳化物数量大幅上升,碳化物面积占比下降。稀土Ce对夹杂物和碳化物的影响有益于M2高速钢性能的提升,研究结果为生产高品质M2高速钢提供了理论支撑。

     

    Abstract: Two heats of M2 high-speed steel with different contents of rare earth (Ce) were produced by a domestic steel plant, optical microscopy, scanning electron microscopy, X-ray diffraction analysis, and high-temperature confocal microscopy are used to explore the effects of Ce on the inclusions and carbides in M2 high-speed steel. After adding Ce, the S content in the electroslag ingot decreases. The inclusions are modified from large-sized and irregular Al2O3 to small-sized and globular CeAlO3. The inclusions are completely modified. Meanwhile, the number density of the inclusions decreases, and the average size is reduced. Thermodynamic calculations show that CeAlO3 inclusions are most likely to be generated in the electroslag ingot, which is consistent with the test results. The eutectic carbides in the as-cast structure of the electroslag ingot are significantly refined. Mismatch calculations show that the mismatch between (001)CeAlO3 and (100)γ-Fe is 4.49%. It can serve as a heterogeneous nucleation core for γ-Fe, promoting the increase of nucleation sites during the solidification process of the molten steel and greatly reducing the growth space of the eutectic carbides. The addition of Ce does not change the type of carbides in the wire rod. The statistical results of carbides in the longitudinal section of the wire rod show that after the addition of Ce, the number of carbides in the same area (1000μm2) increases significantly, while the proportion of the carbide area decreases. The influence of rare earth Ce on inclusions and carbides is beneficial to the improvement of the properties of M2 high-speed steel. The research results provide a theoretical support for the production of high-quality M2 high-speed steel.

     

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