Relationship Between the Trace Elements and Graphite Growth Morphologies in Cast Iron

Muhmond, Haji Muhammad; Fredriksson, Hasse

doi:10.1007/s11661-014-2589-2

Cited by 19 publications

(13 citation statements)

References 14 publications

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“…24,25 Chunky, compacted, vermicular, and irregular graphite particles are commonly observed degenerated graphite elements due to poor treatment of the melt. Even if SGIs are treated to form spheroidal graphite nodules, other forms of graphite particles may grow due to the effect of other trace elements or insufficient addition of inoculant or nodulizer during the solidification process.…”

Section: Introductionmentioning

confidence: 99%

“…Even if SGIs are treated to form spheroidal graphite nodules, other forms of graphite particles may grow due to the effect of other trace elements or insufficient addition of inoculant or nodulizer during the solidification process. 24,25 Chunky, compacted, vermicular, and irregular graphite particles are commonly observed degenerated graphite elements due to poor treatment of the melt. Other elements like S, F, O, P, N, and B can be found in trace quantity in cast irons.…”

Section: Introductionmentioning

confidence: 99%

“…These trace elements in the melt affect graphite nucleation and growth morphology. 25 The effect of these trace elements was divided into 3 parts: S and B as flake graphite stabilizer, O and F stabilizing compacted or vermicular graphite growth, and P and N mostly neutral. It was reported that the graphite growth morphology was related to the impurities in the Fe-based liquid.…”

Section: Introductionmentioning

confidence: 99%

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On the fatigue damage micromechanisms in Si‐solution–strengthened spheroidal graphite cast iron

Sujakhu

Castagne

Sakaguchi

et al. 2017

Fatigue Fract Eng Mat Struct

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Graphite nodules in spheroidal graphite cast iron (SGI) play a vital role in fatigue crack initiation and propagation. Graphite nodules growth morphology can go through transitions to form degenerated graphite elements other than spheroidal graphite nodules in SGI microstructure. These graphite particles significantly influence damage micromechanisms in SGI and could act differently than spheroidal graphite nodules. Most of the damage mechanism studies on SGI focused on the role of spheroidal graphite nodules on the stable crack propagation region. The role of degenerated graphite elements on SGI damage mechanisms has not been frequently studied. In this work, fatigue crack initiation and propagation tests were conducted on EN‐GJS‐500‐14 and observed under scanning electron microscope to understand the damage mechanisms for different graphite shapes. Crack initiation tests showed a dominant influence of degenerated graphite elements where early cracks initiated in the microstructure. Most of the spheroidal graphite nodules were unaffected at the early crack initiation stage, but few of them showed decohesion from the ferrite matrix and internal cracking. In the crack propagation region, graphite/ferrite matrix decohesion was the frequent damage mechanism observed with noticeable crack branching around graphite nodules and the crack passing through degenerated graphite elements. Finally, graphite nodules after decohesion acted like voids which grew and coalesced to form microcracks eventually causing rapid fracture of the remaining section.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On the fatigue damage micromechanisms in Si‐solution–strengthened spheroidal graphite cast iron

Sujakhu

Castagne

Sakaguchi

et al. 2017

Fatigue Fract Eng Mat Struct

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“…This means that coupled growth of graphite and austenite would be preferred even at high eutectic undercooling in pure iron melts, unless spheroidal graphite may nucleate ahead of the cou pled solidification front. Finally, it should be mentioned that Muham mad and Fredriksson [29] have recently reported primary precipita tion of rod like graphite with more or less circular section as coral graphite. 1 In all practicality, adding an inoculant to a cast iron melt eases so lidification in the stable system, while a proper spheroidizing treatment (with magnesium or magnesium and RE) triggers spheroidal growth in stead of lamellar growth.…”

Section: Growth Ratementioning

confidence: 95%

Effects of impurities on graphite shape during solidification of spheroidal graphite cast ions

2019

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This is an author's version published in: http://oatao.univ-toulouse.fr/25345 To cite this version:Lacaze, Jacques and Connétable, Damien and Castro-Román, Manuel Jesus Effects of impurities on graphite shape during solidification of spheroidal graphite cast ions. (2019) Materialia, 8. 100471. ARTICLE INFO ABSTRACT Keyword.s: Cast iron Solidification microstructure Graphite morphology Graphite degeneracy DFTSince the discoveiy that magnesium and cerium (and more generally rare earths) added at low level to cast iron melts lead to spherodized graphite, it is lmown that some other elements are detrimental even when present as traces. In ail practicality, it bas soon been recogniz.ed that adding rare earths to the melt helps counteracting the effect of these detrimental elements. Accordingly, only few works have been devoted to studying the effect of trace elements in melts without any rare earths. This is the first aim of the present work to review those studies as they contain the material to understand the mechanism for spheroidal graphite degeneracy. From this review, three types of degeneracy have been defined which show up when the critical level of any particular element is exceeded. These results are then discussed to show that ail degeneracies certainly proceed in the same way. To substantiate this discussion, the growth of compacted graphite as obtained by low level treatrnent of cast iron melt with magnesium is also presented. Finally, a mechanism is suggested for describing the action of trace elements on spheroidal graphite degeneracy. This mechanism is partly substantiated by first principles calculations which showed that ail elements can strongly adsorb on the prismatic planes which are the planes on which carbon atorns add on during graphite growth. • Corresponding author. E-mail address: jacques.lacaze@ensiacet.fr (J. Lacaze). scription of the impurity effect without RE addition, i.e. concerned with describing and understanding this effect The impurities listed in the patent [4] are As, Bi, Pb, Sb, Se, Sn and Te, and it is worth stressing that most of them are also harmful to non spheroidized lamellar graphite iron melts as reviewed by Rey naud [7]. In an extensive study aimed at controlling the charges for melt preparation, Thielemann [8] proposed the following quality index S b for spheroidal graphite cast irons where Al and Ti appear but not Se and Te which were not considered: S b = 1.6 • w Al+ 2. 0 · w A s + 3 70 · We; + 2 90 · WPb + 5 . 0 · Wsb +2.3 . Wsn +4.4 . WTi (1) in which W; is the weight fraction of i element in the charge used for preparing the melt This quality index has been obtained with spheroidal graphite cast irons containing 0.04 to 0.08 wt. % Mg that were cast with wall thickness in between 8 and 45 mm. When S., is lower than 1 no action is necessary while if it is higher RE should be added to avoid spheroidal graphite degeneracy.What is seen in the Thielemann's factor and which reflects foundry practic e is that bismuth and lead have a much higher coefficient than the other ...

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“…Several researchers have contributed to the understanding of factors influencing growth of graphite work that in 2017 was comprehensively compiled by Stefanescu in ASM Handbook [1]. The use of certain alloying elements to control the shape of graphite during solidification is extensively reported, we now know what causes graphite to grow in the form of spheres or flakes or intermediate forms [3][4][5][6][7][8][9][10]. However, in ductile cast irons, it is common to find a variation in graphite shape, size and distribution, which results in significant variations in mechanical properties [11].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Local Conditions on Graphite Growth and Shape During Solidification of Ductile Cast Iron

Tiedje

Bjerre

Azeem

et al. 2018

Trans Indian Inst Met

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Analysis of local conditions on graphite growth and shape during solidification of ductile cast iron.Abstract 3D X-Ray tomography recordings have been used to study graphite growth during solidification of ductile cast iron. Using data from such recordings, it is shown how local growth conditions influence growth rate and morphology of nodules during solidification. The experiments show that it is common for nodules to gradually change shape during solidification so that sphericity decreases. It is also shown that different shapes of nodules can evolve in direct contact with liquid iron and also after when they are encapsulated in austenite.It is observed that a significant proportion of originally complete spherical nodules become less spherical via formation of protrusions on the surface, these new surfaces are observed to grow relatively faster.It is shown that encapsulation of the graphite nodule by austenite may be incomplete, and that at the end of solidification, partial encapsulation and the effect of the number of nearest graphite nodules play a crucial role in determining the final graphite morphology.

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Relationship Between the Trace Elements and Graphite Growth Morphologies in Cast Iron

Cited by 19 publications

References 14 publications

On the fatigue damage micromechanisms in Si‐solution–strengthened spheroidal graphite cast iron

On the fatigue damage micromechanisms in Si‐solution–strengthened spheroidal graphite cast iron

Effects of impurities on graphite shape during solidification of spheroidal graphite cast ions

Analysis of Local Conditions on Graphite Growth and Shape During Solidification of Ductile Cast Iron

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