Effect Of Ar Purification On Microstructure And Properties Of Gray Cast Iron Cylinder Sleeve By Centrifugal Casting

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.