Abstract
With the aim of improving the thermal conductivity and tensile strength of pearlitic gray cast iron, the influence of inoculation on structure and properties was experimentally investigated. Three group of irons with similar compositions were inoculated by Zr-FeSi, Sr-FeSi, and SiC inoculants, respectively. The metallographic analysis was used to measure the maximum graphite length, primary dendrites amount and eutectic colonies counts. For a certain carbon equivalent, it was confirmed that the thermal conductivity of pearlitic gray cast iron has a direct correlation with the maximum graphite length while the tensile strength was influenced mainly by the primary dendrites amount. The optimal structure and highest thermal conductivity and tensile strength were obtained by Sr-FeSi inoculant. MnS particles act a pivotal part in modifying the structure of gray cast iron. It was found that providing nucleation sites both for graphite and primary austenite is important to promote the thermal conductivity and strength. However, excessive nuclei (MnS particles) results in shorter graphite flakes and thus the depressive growth of primary dendrites.
Highlights
Gray cast iron (GCI) has been considered as the primary choice to produce vital engine components for many decades, the service life is not satisfied yet
For a similar Carbon equivalent (CE), the Zr-FeSi inoculant resulted in the shortest graphite flakes, moderate primary dendrite and moderate size of the eutectic colonies
For a similar CE, it was confirmed that the dominant structural factors in increasing thermal conductivity and tensile strength of pearlitic gray cast iron (GCI) are different
Summary
Gray cast iron (GCI) has been considered as the primary choice to produce vital engine components for many decades, the service life is not satisfied yet. The resistances to the fracture of these GCIs are both closely related to tensile strength and thermal conductivity [2,3]. It is, necessary to develop high performance cast irons (HPCI) with high thermal conductivity while maintaining the high tensile strength. There was a competitive relationship between the thermal conductivity and tensile strength of pearlitic GCI. The principal methods of approving tensile strength are to decrease the fraction of graphite flakes as well as to reduce their length [5,6]. The thermal conductivity can benefit from increasing of the graphite amount and graphite size [7]
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