Graphite, a common allotrope of carbon, is composed of multiple layers of carbon atoms arranged in a hexagonal lattice. Graphene, on the other hand, is a single layer of carbon atoms from this lattice. 10. The layers in graphite are held together by weak van der Waals forces, allowing them to slide over each other easily.
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In hypereutectic nodular cast irons, primary precipitation of graphite may lead to graphite flotation in thick section castings. Graphite degeneracy such as so-called exploded graphite is then often associated with this flotation phenomenon and it appears as precipitates where the nodular form is replaced by star-like or flower-like shape. It has …
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Abstract: Chunky graphite appears easily in heavy-section spheroidal graphite cast irons and is known to a ect their mechanical properties. A dedicated experiment has been developed to study the ... [24] and theorized for the case of exploded graphite [25]. Finally, using the fact that chunky graphite precipitates during coupled …
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Exploded graphite, mainly due to an excess of rare earth additions, Fig. 1; Chunky graphite, due to an excess of rare earth additions, Fig. 2; Compacted graphite, mainly due to low residual ...
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Chunky graphite (CHG) is a well-known phenomenon which occurs in heavy section spheroidal graphite iron (SGI) castings or SGI castings with higher alloying …
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Etching. 3% Nital. Chunky graphite is a degenerate form of spheroidal graphite, so this casting should have been a spheroidal graphite casting (probably around GJS400). The appearance corresponds to an "exploded graphite sphere". The degeneration of the graphite form is promoted by slow cooling and therefore also by thick cross-sections.
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In the thermal centre of the Pb containing sample graphite spheroids as well as intergranular lamellar graphite have been found. At the same location of the casting containing both Pb and Ce, exploded as well as chunky graphite could be observed, while the formation of intergranular lamellar graphite has been suppressed.
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The difference between graphitic steel and ferritic ductile iron is the size and amount of graphite nodules, 5 µm versus 20–50 µm in size and 2 vol.% versus 10 vol.% of graphite. However, size seems to be a minor factor in machinability. Katayama and Toda reported equal machinability for dispersions of 5 µm or 10 µm.
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Stacking of graphite plates was documented earlier for chunky graphite [31]. The conical sectors may occupy the whole volume of the sphere forming a graphite spheroid, or only part of it like in exploded graphite. Chunky graphite can be the product of a succession of conical sectors growing on top of one another.
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inclusions while the larger cubes had chunky graphite. Chunky graphite morphology negatively affect the mechanical properties of cast iron due to undercooling and presence of trace elements. Sertucha et al. [5] showed the eutectic undercooling versus growth rate for chunky gra-phite (CHG) and nodular graphite (spheroidal) in a recent publication.
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Abstract Use of rare earths, high silicon and carbon contents, and low cooling rates are reported as possible reasons for formation of chunky graphite in ductile iron castings. The understanding of this graphite degeneration is however limited, and the above conclusions are still controversial. To get further insight into this topic, ductile cast …
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The importance of melt chemistry on graphite shape is well known, and the effect of impurities or alloying elements on the change from spheroidal to chunky graphite at given growth conditions is ...
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The chunky graphite formation stems from the lower amount of sulphur content, which is 0.008wt% in specimen A-3. As stated in previous works [8], [9], low levels of sulphur (<0.010wt%) enhance the ...
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The nodularity was evaluated to 73.5 %. The microstructure in Fig. 2-b (SG-PbCe alloy) shows no intergranular flake graphite but exploded graphite as well as chunky …
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Chunky graphite is one of the most deleterious graphite degenerations in thick-walled ductile-iron castings. This defect normally appears in the thermal center of a casting and dramatically decreases the mechanical properties. Chunky-graphite formation is primarily caused by a reduction in the cooling rate and melt composition.
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Chunky graphite appears easily in heavy-section spheroidal graphite cast irons and is known to affect their mechanical properties. A dedicated experiment has been developed to study the effect of the most important chemical variables reported to change the amount of chunky graphite, namely the content in silicon and in rare earths. Quite …
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Graphite Nodularity (NG3), calculated with the ISO 945-4-2019 [DI] formula, but replacing RSF with SSF, Sphericity Graphite Shape Factor, has an intermediary position. ... (spiky graphite), exploded graphite, chunky graphite, etc. In comparison to steel, while there is no large difference when it comes to tensile strength, ductile iron has ...
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A Review of Common Metallurgical Defects in Ductile Cast Iron – …. Ductile Cast Iron Causes and Cures C.M.Ecob Customer Services Manager, Elkem AS, Foundry Products Division Abstract …exploded and chunky graphite, … » Free online chat! Material, AutoCad and Fun: Common Defects in Ductile Cast Iron. Feb 12, 2009 · … an overview …
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Special emphasis was laid on providing a comprehensive overview on the impact of chunky graphite on strength, ductility, fatigue limit, fatigue crack growth rate …
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While the specialists almost unanimously claim that avoidance of chunky graphite in heavy sections cannot yet be rated a hundred percent process safe, 2,6,7,[13][14] [15] [16][17][18][19][20] a ...
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In the first group are chunky graphite (CHG) and exploded graphite (EG) whereby EG is an intermediate between regular nodular graphite and CHG. 7, 8 Intercellular lamellar graphite (ILG ...
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There is a big difference between the graphite nodularity evaluated according to ISO 16112:2017 [CGI] (NG1 = 79–86%) and according to ISO 945-4-2019 …
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The followings were confirmed in this study. (1) Exploded graphite appears when RE contents are above 0.02 mass%. (2) Chunky graphite does not appear when the Sb/RE ratio is above 0.7. The cause of the chunky graphite appearance will be studied next. 21 refs., 5 figs., 4 tabs.
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As discussed earlier for metamorphic graphite, helical growth can lead to the formation of holes in the middle of graphite aggregates. This is illustrated in Fig. 11-b for the case of chunky graphite. Growth through the foliated dendrites mechanism is also shown in Fig. 11-c for a different region of the chunky graphite.
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Expanded graphite is multi-porous (2–10 nm) and average pore size of ~2 mm. This form of graphite can be readily intercalated and host molecules including monomers and polymers can be incorporated between the expanded graphene sheets to form modified composite structure. EG has been developed as polymer reinforcement in early 1900s …
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chunky and exploded graphite. The imprecise term degenerated graphite along with mixing of chunky, compacted and exploded graphite can generate confusion. With the recent …
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Silicon is one of the elements that tend toward chunky graphite formation. By comparing the effect of Si and Ni on chunky graphite in heavy castings (micro/macro analysis), it was found that higher Si has a strong influence on chunky graphite formation, especially in castings with a slow cooling rate, while Ni promotes chunky graphite only …
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Abstract and Figures. Antimony is used in ductile cast iron melts to avoid graphite degenerations like exploded graphite and chunky graphite. However, the effect of Sb in the melt on the ...
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Microstructure shows variation in the graphite structure from nodular to chunky and at some locations exploded graphite. The Carbon Equivalent is 4.783% …
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The higher the imposed minimum RSF or SSF is, the lower the Graphite Nodularity (NG4, NG5): 80–90% for min. 0.50 (minimum Form IV or Intermediate Graphite), 60–80% for min. 0.60–0.65 (minimum Form V graphite) and 35–70% for min. 0.80 (minimum Form VI graphite). The SSF is more representative than the RSF for Si-alloyed ductile cast iron ...
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Understanding spheroidal graphite growth in cast irons is a long standing problem for which several mechanisms have been proposed. During the last decade, observations using transmission electron microscopy added new information about the stacking of graphite layers, leading eventually to propose other mechanisms than …
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Microstructure shows variation in the graphite structure from nodular to chunky and at some locations exploded graphite. The Carbon Equivalent is 4.783% which indicates towards hyper-eutectic side, this is one of the strong reasons for the formation of chunky and exploded graphite.
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Different mechanisms have been proposed for the formation of exploded graphite. Considering that nodularizers facilitate nucleation into basal planes with growth mainly occurring in the prismatic ...
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Fig. 2. Pattern of Casting. Melting was realised in the medium-frequency inductive furnace with the acidic lining with the volume of 10 ton. As the charge used was the steel scrap (SVa), pig iron ...
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Pursuant to an early proposal of Karsay et al.,28 chunky graphite emanates from small pieces broken off the ordinary graphite nodules. Due to thermal currents and growth …
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Several different graphite morphologies such as vermicular, spiky, coral, exploded and chunky graphite have been observed to form in the thermal center of heavy ductile iron sections during solidification [2]. The location of chunky graphite normally, but not exclusively, indicates the location of the thermal center of a casting [3].
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These cast irons could also include other unwanted graphite morphologies, such as degenerated form (spiky graphite), exploded graphite, chunky graphite, etc. …
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Download scientific diagram | Chunky graphite share determined on the fracture surface versus chunky graphite share determined on microsections of a fracture mechanics specimen, disk-shaped ...
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graphite, namely chunky graphite [13,14]. From a metallurgical point of view, the main feature of chunky graphite is that its overall growth direction is along the basal c direction of graphite as it is for spheroidal graphite. Thus, the growth mechanism of chunky graphite certainly differs from the one mentioned above for protrusions.
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