| Summary: | 碩士 === 逢甲大學 === 材料與製造工程所 === 99 === The objective of this research is to investigate the effect of adding alloying element Cu, Sn independently on the metallographic microstructure (graphite, matrix etc.)and mechanical properties (tensile strength, hardness, impact value etc.) of furan resin mold flake and spheroidal graphite cast iron.
The result of experiment shows that when alloying element Cu, Sn was added to flake and spheroidal cast iron, in the metallographic microstructure, with the increasing of Cu, Sn added amount, the flake graphite changes from coarse to fine, diameter of nodular graphite becomes small, nodular count becomes increase, nodularity is not affected but greater than 90%.
In addition, the pearlite in the microstructure would be refined. For example of flake graphite cast iron FC350, when added with 0.23wt% Cu, the average lamella thickness of cementite and ferrite is 190.76nm and 218.5nm respectively. But when increased to 1.9wt%Cu addition, the average lamella thickness of cementite and ferrite is 152.21nm and 140.08nm. When 0.027wt%Sn was added, the average lamella thickness of cementite and ferrite is 432.06nm and 276.01nm. But when Snwt% was increased to 0.173wt%, the average lamella thickness of cementite and ferrite is decreased to 233.06nm and 157.57nm. By SEM/EDS find that, with the increasing of alloying element Cu & Sn are easy to segregate on the pearlite grain boundary.
In the mechanical properties, flake and spheroidal graphite cast iron have same trend for adding Cu and Sn. But with the same amount added, the effect on spheroidal graphite cast iron is more than it on flake graphite cast iron. When adding alloying element Cu, tensile strength and hardness increased gradually, but the impact value decreased gradually. When adding alloying element Sn, hardness increased gradually, but the impact value decreased gradually with the increasing of Snwt%. For the tensile strength it will increases gradually at first, but when the wt% of alloy element Sn is greater than a certain value, the trend of the tensile strength will decrease obviously.
This research also use the obtained experiment result data to calculate the regression equation of the alloying addition amount respect to mechanical properties. Its accuracy is high(r2>0.9), and should be able used to predict the relation between the alloying elements Cu, Sn addition amount and the mechanical properties of flake and spheroidal graphite cast iron castings in the future.
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