Study on the High Temperature Thermal Fatigue Property of Thin-Section Compacted Graphite ast Iron
Date Issued
2009
Date
2009
Author(s)
Cheng, Chin-Hua
Abstract
The primary purpose of this research is to establish the optimal conditions for the production of thin-section (2?3 mm) compacted graphite cast irons for high temperature applications (up to 800℃). Experimentally, the microstructures (include vermicularity, graphite count, and matrix structure) and thermal fatigue property will be evaluated and correlated with alloy design and casting parameters, such as section size and molding material. The results show that, for a fixed C content of some 2.88% and Si content of some 5.0%, an addition of about 0.3% compactizing alloys can attain compacted graphite structure. Regarding the effects of casting parameters on microstructure, the results show that for fixed C and Si contents higher graphite counts can be obtained in castings with a thinner section, while, higher vermicularity can be obtained in castings with a thicker section. However, the effect of molding material on graphite count and vermicularity are not significant. For a fixed C content (3.0%) and treatment conditions (compactizer 0.3%、inoculant 0.15%), both the %ferrite and graphite count increase with increasing Si content, reach maxima at around 4.6% Si.he result about thermal fatigue show that, for fixed C and Si content and vermicularity, thermal fatigue cycles to failure increases with increasing %ferrite and graphite count. Further, under the conditions of fixed graphite count and ferrite content, thermal fatigue cycle increases first with increasing vermicularity, reaches maximum, and then decreases with further increases in vermicularity. ixed C content of 3.0% and constant treatment conditions (compactizer 0.3%, inoculant 0.15%), the thermal fatigue cycle increases with increasing Si content. Similar trends have also been obtained for graphite count and %ferrite. Furthermore, adding some 0.5% Mo can significantly increase thermal fatigue cycles to failure.inally, the fracture mechanism during the thermal fatigue test had also been assessed in this study.
Subjects
thin-section compacted graphite cast iron, graphite count, vermicularity, thermal fatigue property, secondary graphite.
Type
thesis
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