【作者】 杨娟；

【导师】 刘胜新； 侯起飞；

【作者基本信息】 郑州大学 ， 材料加工工程， 2011， 硕士

【摘要】 灰铸铁具有良好的性能,已成为一种重要的工程结构材料,某些铸件所用材料除灰铸铁之外其他材料还无法取代。目前,针对离心铸造灰铸铁气缸套,化学成分及组织相近时,进口件的抗拉强度和弹性模量都高于国产件,而且硬度低、切削加工性能好。经研究可知,进口件的铁液纯净度高、材质均匀性好、组织中夹杂物含量少。铁液质量包括铁液温度、化学成分和纯净度。目前,生产中铁液温度和化学成分可准确控制,但在保证优质铁液、生产高强度和高刚度的优质铸件等方面一直没有突破性进展。本文以中原内配股份有限公司实际生产的合金成分和熔炼工艺为基础,通过孕育剂优化试验筛选出合适的复合孕育剂,同时将吹氩用于离心铸造灰铸铁气缸套的熔炼过程,采用金相显微镜、扫描电镜、拉伸试验机等设备分析吹氩处理前后灰铸铁的显微组织,测定抗拉强度、弹性模量等机械性能,并对灰铸铁的冶金性能进行评估,得出以下结论：1.采用炉内增硫0.06%+硅锶随流孕育处理,灰铸铁组织中石墨呈细小片状、分布均匀,夹杂物的数量最少,抗拉强度和弹性模量等性能同时提高,综合性能最好。2.吹氩处理前后,灰铸铁组织中的氧化夹杂以颗粒点状和附着在石墨周围的块状或絮状形式存在。吹氩处理使组织中的氧化夹杂数量大大减少,石墨形态得到改善,共晶团的数量增加23%,渗碳体的层片状结构变得较为弯曲、方向性发生小角度改变。3.吹氩处理前,灰铸铁的抗拉强度350MPa左右,吹氩处理后,抗拉强度达380MPa左右,最高达到390MPa左右,弹性模提高到122GPa,提高了10%左右,灰铸铁的成熟度为1.13,品质系数为1.11,相对硬度RH较低,综合性能良好。更多还原

【Abstract】 Gray cast iron possesses excellent technological performance. Therefore, gray cast iron is widely used as one of the most important structural materials and it cannot be replaced in some special castings. For gray cast iron cylinder sleeve by centrifugal casting, properties of import parts are higher than that of local parts with the similar chemical composition and the microstructure in gray cast iron. At the same time, the imported parts have lower hardness and better cutting performance resulting from better quality of molten iron, more uniform microstructure and fewer impurities. The temperature, chemical composition and purity are included in the quality of molten iron. The temperature and chemical composition of molten iron can be effectively controlled. However, good quality of molten iron and castings with high strength and stiffness are unattainable at present.Under the determinate conditions of alloy composition and smelting processes, inoculants for gray cast iron was optimized. On the basis of optimization, the samples without blowing argon and the argon-blowing ones were studied. The microstructures were observed by an optical microscope and the electron microscope. The mechanical properties were tested on a universal testing machine. In addition, the results of metallurgical performance were measured. The main research results are summarized as follows:First, in test of inoculants optimum design, the samples have higher tensile strength, better elastic modulus and fewer impurities when it is inoculated by silicon-strontium-sulfur compound inoculants.Second, in the microstructures, the granular substance and woolly masses attached to graphite are forms of existence of impurities. The number of impurities is decreased and the degeneration of normal graphite is improved by argon-blowing processing. The effects of blowing argon on microstructures of gray cast iron is obtained. The number of eutectic cells is increased from 573 to 705 per square centimeter. After argon-blowing processing, the lamellar of cementite is more curved and changed with a small angle range in direction. Third, the tensile strength, the elastic modulus and the indexes of metallurgical quality are analyzed comprehensively. The tensile strength without blowing argon is 320MPa, up to 360MPa with the elastic modulus 108GPa; After argon-blowing processing, the tensile strength is raised over 360MPa, even up to 390MPa and the elastic modulus is improved to 122GPa. The maturity of gray cast iron is improved from 1.0549 to 1.1324, with the lower relative resistance and the better comprehensive properties.更多还原