Influence of Trace Elemients Oh Graphite Forms in Cast Iron

1984 ◽  
Vol 34 ◽  
Author(s):  
R. D. Bhavsar ◽  
N. W. Blake ◽  
B. Ghoreshy ◽  
T. W. Smith
Keyword(s):  
Cast Iron ◽  
Alloy Composition ◽  
High Magnification ◽  
Compacted Graphite ◽  
Controlled Conditions ◽  
Graphite Morphology ◽  
Rate Of Cooling ◽  
Graphite Growth

ABSTRACTSynthetic and commercial Fe-C-Si irons have been frozen under controlled conditions after vacuum purification in order to correlate graphite forms with freezing conditions and alloy composition. It was found that graphite morphology was influenced prirmarily by the sulphur and oxygen contents and the rate of cooling. The various modes of graphite growth are discussed, particularly the appearance of the coral and compacted graphite surfaces at high magnification after the addition of oxygen or nitrogen.

Graphite Morphology Control in Cast Iron

1984 ◽  
Vol 34 ◽  
Author(s):  
S. V. Subramanian ◽  
D. A. R. Kay ◽  
G. R. Purdy
Keyword(s):  
Cast Iron ◽  
Growth Mechanism ◽  
Driving Forces ◽  
Morphology Control ◽  
Spiral Growth ◽  
Compacted Graphite ◽  
Spherulitic Morphology ◽  
Graphite Morphology ◽  
Control Diagram ◽  
Graphite Growth

ABSTRACTGraphite morphology in cast iron is analyzed in terms of the growth kinetics of graphite crystals in liquid iron. At small driving forces, i.e., low supersaturation or small kinetic undercooling, graphite growth is characterized by faceted growth, resulting in flake, compacted and spherulitic graphite morphologies. However, at large driving forces, there is a transition from facted to non-faceted growth, resulting in a dendritic growth morphology.Flake morphology is rationalized in terms of impurity dependent crystal growth mechanisms, whereas a spherulitic morphology is attributed to a defect controlled spiral growth mechanism. Compacted graphite morphology is considered as a transition between flake and spherulitic morphology.A thermodynamic approach is used to inter-relate the residual concentrations of impurities of technological interest, i.e. S and 0, as a function of the residual concentration of the reactive elements, Mg, Ca, and Ce in a typical cast iron melt at 1500'C and atmospheric pressure. Such a diagram that quantitatively relates graphite morphology in thick cast iron sections to soluble concentrations of impurities is referred to as a graphite morphology control diagram.In thin section castings that freeze at faster cooling rates and large kinetic undercoolings, the basal spiral growth mechanism dominates over the impurity controlled prism growth mechanism, leading to deviations from predictions based simply on the graphite morphology control diagram. In the ase of compacted graphite, where growth on both the prism and basal faces is involved, the degree of nodularity increases with the cooling rate, giving rise to section sensitivity.At large undercoolings, the prevention of the nucleation and growth of cementite is an essential feature of graphite morphology control. It is estimated that the mobility of the cementite interface exceeds that of the prism interface in flake graphite growth by an order of magnitude and that of the basal interface in spherulitic graphite growth by three orders of magnitude. In practice, the driving force for graphite growth is raised selectively through the addition of graphite stabilizing elements, such as silicon, which raise the temperature of the graphite eutectic and depress the temperature of the carbide eutectic. Kinetic growth undercooling can be decreased by increasing the number of heterogeneous nuclei for graphite growth through inoculation. The application of the above concepts for the control of graphite morphology in shaped automotive castings is discussed.

Graphite Growth Morphologies in Cast Iron

2014 ◽  
Vol 790-791 ◽  
pp. 458-463 ◽  
Author(s):  
Haji Muhammad Muhmond ◽  
Hasse Fredriksson
Keyword(s):  
Cast Iron ◽  
Ternary Alloy ◽  
Growth Mechanism ◽  
Eutectic Composition ◽  
Flake Graphite ◽  
Growth Morphology ◽  
Ion Etching ◽  
Graphite Morphology ◽  
Graphite Growth ◽  
Melt Composition

Graphite growth morphology was studied by using InLense detector on FEG-SEM after performing ion etching on the samples. Star like and circumferential growth mechanism of graphite was observed in the graphite nodules. Pure ternary alloy of hypo eutectic and hyper eutectic composition was treated with pure Mg, Ca and Sr, to study the effect of O and S concentration in the melt, on the transition of graphite morphology from nodular to vermicular/compacted and flake graphite. The change in the melt composition between the austenite dendrites due to micro-segregation of S, O and inoculants and their possible effects on the transition of graphite morphologies as well as the nucleation of new oxides/sulfides particles is discussed with the help of thermodynamics.

The Effect of Magnesium to Sulfur Ratio on the Graphite Morphology of Graphite Cast Iron Produced at Differrent Section Thicknesses

2011 ◽  
Vol 383-390 ◽  
pp. 5880-5885
Author(s):  
Omar Elmabrouk ◽  
Osama M. Erfan ◽  
Ali Kalkanli
Keyword(s):  
Mechanical Properties ◽  
Cast Iron ◽  
Ductile Cast Iron ◽  
Flake Graphite ◽  
Factors Affecting ◽  
Compacted Graphite ◽  
Graphite Particles ◽  
Graphite Morphology ◽  
Graphite Cast Iron ◽  
Flake Graphite Cast Iron

This paper is concerned with the investigation of the effect of magnesium to sulfur ratio on the graphite morphology and estimation of the ranges of this ratio use to produce graphite cast iron at different section sections. The main factors affecting shape of graphite cast iron are the metallurgical structures and the section thicknesses. Cast iron of different shapes of graphite particles directly affect its thermo-mechanical properties. The nodular shape of these graphite particles such as in ductile cast iron improve its mechanical properties, on the other hand, when the shape of these graphite particles become elongated such as in flake graphite cast iron results in improving its thermal conductivity. In between, the worm-like shape of these graphite particles such as in compacted graphite cast iron, make this type of cast iron to have thermo-mechanical properties in between those of ductile and flake graphite cast iron. The different types of ductile , compacted and flake graphite cast iron were produced by means of plunger method at different section thicknesses and the effect of Mg/S ratio on these types of graphite particles was investigated and its range was established.

scholarly journals Unraveling compacted graphite evolution during solidification of cast iron using in-situ synchrotron X-ray tomography

Carbon ◽  
2021 ◽  
Author(s):  
Chaoling Xu ◽  
Tim Wigger ◽  
Mohammed A. Azeem ◽  
Tito Andriollo ◽  
Søren Fæster ◽  
...  
Keyword(s):  
Cast Iron ◽  
X Ray ◽  
Compacted Graphite

scholarly journals Revisiting Models for Spheroidal Graphite Growth

2018 ◽  
Vol 925 ◽  
pp. 118-124 ◽  
Author(s):  
Mathias Karsten Bjerre ◽  
Mohammed Azeem ◽  
Peter D. Lee ◽  
Jesper Henri Hattel ◽  
Niels Skat Tiedje
Keyword(s):  
Growth Rate ◽  
Cast Iron ◽  
Numerical Model ◽  
Final Stage ◽  
Nucleation And Growth ◽  
Ductile Cast Iron ◽  
Spheroidal Graphite ◽  
Microstructure Formation ◽  
X Ray ◽  
Graphite Growth

Recent experiments resolved nucleation and growth of graphite during solidification of ductile cast iron in 4D using synchrotron X-ray tomography. A numerical model for microstructure formation during solidification is compared with the experiments. Despite very good overall agreement between observations of spheroidal graphite growth and model results, significant deviations exist towards the end of solidification. We use the experimental observations to analyse the relation between graphite growth rate and the state of the particle neighbourhood to pinpoint possible links between growth rate of individual graphite spheres and the overall solidification state. With this insight we revisit existing models for growth of spheroidal graphite and discuss possible modifications in order to correctly describe the critical final stage of solidification.

Thermal Conductivity Analysis of Compacted Graphite Cast Iron After a Creep Test

2019 ◽  
Vol 50 (8) ◽  
pp. 3697-3704
Author(s):  
Wu Yue ◽  
Li Jianping ◽  
Yang Zhong ◽  
Guo Yongchun ◽  
Ma Zhijun ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Cast Iron ◽  
Creep Test ◽  
Compacted Graphite ◽  
Graphite Cast Iron
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