توليد و مشخصه يابي چدن خاكستري هايپر يوتكتيك نيمه جامد به روش SSR همراه با افزودن نانو مواد جوانه زا

چكيده انگليسي :

Production and Characterization of Semisolid Hypereutectic Grey Cast Iron Through SSR Process with Addition of Nano Size Inoculants Sayed Ali Akbar Sedighi Ghaleh Ghasemi sa sedighi@ma iut ac ir Date of Submission 3 14 2012 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor Behzad Niroumand behzn@cc iut ac irAbstractSemi solid casting has been studied and used as one of the rather new ways of manufacturingmetallic parts due to its advantages over other common casting processes The majority of thestudies were on low melting point alloys and ferrous and high melting point alloys haveattracted less attention In the present study the microstructure and properties of a SSR casthypereutectic gray cast iron was evaluated SSR is a semi solid casting process based on localcooling of the liquid phase and producing and dispersing nuclei into it Presence of a lot oflarge Kish graphites in the microstructure of a hypereutectic gray cast iron results in lowmechanical properties Hypereutectic gray cast irons have remarkable physical properties suchas high heat transfer ability and high trembling absorption ability so in case of bettermicrostructure and mechanical properties they could make more efficient metallic products Inthis research first the ingot with distinguishing composition was made and after melting andSSR treatment of the alloy it was poured into two sandy and metallic molds and pressed bysqueezing As the next step micro and nano size inoculants were added to the liquid phase forcasting Then the effect of different treatments on microstructures physical and mechanicalproperties were evaluated The results showed that semi solid casting of a hypereutectic graycast iron changed the dendritic microstructure to spherical made the graphites smaller removed Kish graphites and produced D type graphites The microstructures underwent morechanges in the cases of metallic mold pressing and adding inoculants The effect of two typesnano size and micro size inoculant wasn t very different on mechanical properties andmicrostructure SSR treatment resulted in higher densities of the samples and the squeezingwas also effective so that the density increased from 7 05gram per cubic centimetre for thesand cast refrence sample to 7 4 gram per cubic centimetre for the squeezed one Themicrostructural changes improved the electrical resistivity from 3 9 10 4 ohm centimeter forthe sand cast reference sample to 1 47 10 4 ohm centimeter for the SSR treated and squeezedone Based on mechanical tests the improvement in microstructure and graphite morphologyresulted in higher tensile strength bending strength hardness and wear resistance The tensileand bending strength increased from 116 3MPa for the sand cast reference sample to168 9MPa for the SSR treated with addition of nano size inoculant and from 254 9MPa for thesand cast reference sample to 424 7MPa for the SSR treated with addition of nano sizeinoculant respectively for the SSR treated sample containing nano size inoculants SSR treatedand squeezed sample had the highest hardness and it was 215 6HV It referred to its highdensity and also the structure and morphology of the graphites The under pressure solidifiedsample had the highest wear resistivity Larger Kish graphites and lower D type grapitesresulted in better lubrication and higher wear resistance of reference samples Key wordsSemi solid casting SSR method Hypereutectic gray cast iron Nanosize inoculant Mechanicalproperties

صديقي قلعه قاسمي، علي اكبر

توليد و مشخصه يابي چدن خاكستري هايپر يوتكتيك نيمه جامد به روش SSR همراه با افزودن نانو مواد جوانه زا

ريخته گري نيمه جامد , خواص مكانيكي