Recent Developments in Understanding Nucleation and Crystallization of Spheroidal Graphite in Iron-Carbon-Silicon Alloys

Abstract

The last decade has witnessed significant research efforts directed to the understanding of nucleation and crystallization of graphite and associated solidification phenomena, driven in part by the ever-growing interest in the use of spheroidal graphite cast iron in the manufacture of large castings, such as wind turbine parts. These applications raised new challenges to the production of sound castings, mostly because of the exceedingly long solidification times imposed by the size of the castings. These solidification conditions resulted in many instances in graphite degeneration with subsequent decrease in mechanical properties. Obviously, the subject of graphite nucleation and crystallization in cast iron is still in need of additional answers. Over the years, many reviews of the subject have been published. The goal of this paper is to provide an update on the advances achieved in comprehending the mechanisms that govern the nucleation and crystallization of spheroidal graphite and related imperfect morphologies from iron-carbon-silicon melts. In this analysis, we examine not only the crystallization of graphite in cast iron, but also that of metamorphic graphite (natural graphite formed through transformation by heat, pressure, or other natural actions), and of other materials with similar lattice structure and crystallization morphologies.

90 years of thermal analysis as a control tool in the melting of cast iron

“…An important issue in the production of heavy section ductile iron castings is the avoidance of chunky graphite (CHG). It is currently an active subject of research as evident in some recent reviews [44,45] . Attempts have been made to correlate crystallization of chunky graphite with parameters of the cooling curve.…”

Study of the effect of nanomodifiers from silicon production wastes on morphological form of gray cast iron graphites

“…Its typical morphological features on the surface of metallographic specimen are noted as "round, thickened and mostly unbranched short graphite plates". It is known [11][12][13][14][15]23], that vermicular graphite form provides not only increased mechanical properties of cast iron, but also varying of physical (heat conductivity) and casting (linear and volumetric shrinkage) properties. The mechanism of vermicular graphite forming is observed in the work [28], where especial role of non-metallic inclusions in the process of graphite forming is underlined.…”

“…Such elements as Cu, Si and Sn cause only slight variations of graphite form morphology. The authors of the work [13] tried to present the renewed information about achievements obtained in understanding of the mechanisms that control and manage nucleation and crystallization of spheroidal graphite and connected with it imperfect morphologies from Fe-C-Si melts. The authors of the work [14] did not agree with false affirmations made in [13], and discussion started [15].…”

“…The authors of the work [13] tried to present the renewed information about achievements obtained in understanding of the mechanisms that control and manage nucleation and crystallization of spheroidal graphite and connected with it imperfect morphologies from Fe-C-Si melts. The authors of the work [14] did not agree with false affirmations made in [13], and discussion started [15]. At recent time the tendency of use of nanomodifiers for improvement of gray cast iron properties can be noted [16][17][18][19][20][21][22].…”

Density and surface tension of molten cast irons

“…Since not only the amount of graphite but first its morphology significantly influences the properties and performance of cast iron components, many studies were focused on understanding factors affecting the nucleation and grows of graphite phase from Fe-C melts (e.g. [3,[8][9][10][11]). Shi et al [12] made an attempt to establish experimentally the specific relationship between the surface tension of cast iron and the graphite shape.…”