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选用3种具有不同Ce含量的球化剂FeSiMg6RE2、FeSiMg8RE3和FeSiMg8RE5对铁液进行盖包法处理,球化处理后浇注成180mm×180mm×200mm的球铁试块。通过室温拉伸、光学显微镜(OM)、扫描电子显微镜(SEM)、能谱分析仪(EDS)和低温冲击试验机等分析手段,研究了稀土元素Ce对大断面低温球铁的石墨组织、力学性能和低温冲击韧性的影响。结果表明:用稀土含量低的球化剂FeSiMg6RE2进行处理,试样的石墨组织细小均匀,石墨形态好,低温冲击韧性高,冲击功平均值约为14.5J;用稀土含量高的球化剂FeSiMg8RE3和FeSiMg8RE5分别进行处理,试样中出现了大面积碎块状石墨等变异组织,低温冲击韧性差,冲击功平均值分别约为6.5和5.1J。能谱分析结果表明:高稀土含量球化剂处理的球铁试样,石墨组织晶界上发生了稀土元素Ce的富集,其质量分数分别约为0.36%和0.42%,这是造成铸件中碎块状石墨等变异组织产生的根本原因,严重恶化了铸件的力学性能。
Three kinds of nodularizing agents FeSiMg6RE2, FeSiMg8RE3 and FeSiMg8RE5 with different Ce contents were selected to treat the hot metal. The spheroidizing process was poured into a ductile iron test piece of 180mm × 180mm × 200mm. The effects of rare earth element Ce on the microstructure and mechanical properties of graphite with large cross section and low temperature ductile iron were investigated by stretching at room temperature, optical microscope (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and low temperature impact tester. Performance and low temperature impact toughness. The results show that the graphite microstructure of the sample is fine and uniform, the shape of graphite is good, the impact toughness is high at low temperature, and the average value of impact energy is about 14.5J. When FeSiMg6RE2 with low rare earth content is used, And FeSiMg8RE5 were treated, the sample appeared in a large area of crumb-like graphite and other microstructures, low temperature impact toughness, the average impact energy were about 6.5 and 5.1J. The results of energy spectrum analysis showed that the rare earth element Ce enrichment occurred on the sample of ductile iron with high rare earth content nodularizer and the mass fraction of rare earth element Ce was about 0.36% and 0.42%, respectively, Broken pieces of graphite and other root causes of variation of tissue, seriously deteriorating the mechanical properties of castings.