摘要：为改善中碳高硫易切削钢中MnS夹杂物形貌特征，在2kg真空感应炉开展了钢中添加Zr金属的试验。利用SEM-EDS研究了不同Zr含量下钢中氧化物和硫化物的形貌特征，并利用Thermo-Calc软件分析了中碳高硫易切削钢中不同种类MnS的形成过程和机制。结果表明：不添加Zr元素的试验钢中，硫化物主要为簇状形貌的II类，以及少量大尺寸的I类，尺寸和空间分布都很不均匀。加了质量分数为0.0015%的Zr元素后，钢中硫化物基本上是以沿晶界分布的簇状形貌存在，复合硫化物占比只有0.1%。随着Zr质量分数进一步增加至0.0051%，钢中主要生成细小的、纯ZrO2氧化物粒子，为硫化物提供了大量形核核心，减弱了硫化物在晶界聚集的分布行为，提高了硫化物的分布均匀性。试验结果表明，高硫氧比条件下，同样可以利用钢中氧化物粒子改善MnS形貌，关键是得到细小尺寸、高效形核效果的第二相粒子。

Abstract：In order to improve the morphology characteristics of MnS inclusions in medium carbon high sulfur free-cutting steel, Zr alloy with different contents were added into the 2kg vacuum induction furnace in laboratory, and the characteristics of oxides and sulfides in steel with different Zr additions were investigated with scanning electron microscope and energy dispersive spectrometer (SEM-EDS). The formation mechanism and process of different MnS inclusions were analyzed with thermodynamic software Thermo-Calc. The results show that sulfides in the experimental steel without Zr element are mainly type II MnS with cluster morphology and a small number of type I MnS with large size, and the size and spatial distribution of the sulfides are extremely uneven. After adding 0.0015 mass% of Zr element, the sulfides in the steel are mainly distributed along the grain boundary with cluster morphology. Complex sulfides account for only 01%. As the Zr content further increases to 0.0051 mass%, fine and pure ZrO2 particles are generated in the steel, which provides a sufficient oxide nucleus for MnS formation, weakens the distribution behavior of sulfides in grain boundary polymers, and improves the distribution uniformity of sulfides. Thus, oxides in steel can be used to improve the morphology of sulfides even under the condition of high S/O ratio. The key is to obtain secondphase particles with fine size and efficient nucleation ability.