Effects of high silicon contents on graphite morphology and room temperature mechanical properties of as-cast ferritic ductile cast irons. Part I – Microstructure

González-Martínez, R.; Torre, Urko de la; Lacaze, Jacques; Sertucha, Jon

doi:10.1016/j.msea.2017.11.050

Cited by 34 publications

(40 citation statements)

References 15 publications

(20 reference statements)

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“…Further, this amount increases in this latter case with either or both increase in silicon and magnesium. Analysis of the series of castings from which the present samples were selected suggested defi ning the following index [5] :…”

Section: Discussionmentioning

confidence: 99%

“…All experimental details for melt preparation have already been given [5] . Magnesium treatment was performed following the socalled sandwich method by transferring 50 kg of the prepared melt to a ladle where FeSiMg alloy (grain size 5-25 mm, Si = 46.60, Mg = 6.00, Ca = 0.96, Al = 0.71 and rare earth RE = 0.92, Fe balance, wt.%) had been positioned in an amount of 0.6 kg (1.2 wt.% of the batch weight) and then covered with steel scrap (grain size 5-15 mm).…”

Section: Methodsmentioning

confidence: 99%

“…As part of a study devoted to high-silicon spheroidal graphite cast irons [5] , it appeared of interest to perform differential thermal analysis (DTA) on samples machined out of materials showing various amounts of chunky graphite. Indeed, such an analysis had been performed previously on a common SGI which showed DTA samples consisted of either spheroidal/compacted graphite or lamellar graphite after remelting and resolidifi cation [6] .…”

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Some paradoxical observations about spheroidal graphite degeneracy

Lacaze

Sertucha

2018

China Foundry

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T he control of graphite shape in spheroidal graphite cast irons is primarily achieved by limited additions of magnesium, though rare earths may also be added to sustain the spheroidization treatment. To avoid fading of the spheroidization treatment, in particular when casting heavy-section parts, it could be tempting to overtreat the melt. However, it has been long recognized that magnesium and rare earth over-treatment leads to spheroidal graphite degenerating in chunky graphite. Conversely, under-treatment in magnesium or rare earths is the most usual way of preparing melts for obtaining compacted graphite which may thus be seen as another type of spheroidal graphite degeneracy, though a more appropriate way of thinking would consider it as "a balance between fl ake and nodular graphite" [1]. Except spheroidal graphite, all solidifi cation forms of

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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confidence: 99%

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Some paradoxical observations about spheroidal graphite degeneracy

Lacaze

Sertucha

2018

China Foundry

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“…Due to the demand of improving mechanical properties, new chemical compositions and production routes of Ductile Irons (DIs) have been explored to obtain different microstructures. Thus, new classes of advanced DIs have been produced, that are, for instance, the alloyed SiBoDur [1] and High Silicon Strengthened (HSiS) DIs, i.e., with silicon content above 3.5-4.0 wt% [2][3][4], and the Austempered DIs (ADIs) [5][6][7][8] and Isothermed DIs (IDIs) [8] that are produced through heat treatments. The current international standards were originally produced for classifying conventional DIs, where silicon content is almost constant (1.8-2.8 wt%) and the pearlite to ferrite ratio, changing because of alloying elements like copper, is the key microstructure parameter that increases yield and tensile strengths, and reduces elongations to rupture.…”

Section: Introductionmentioning

confidence: 99%

Validation of a New Quality Assessment Procedure for Ductile Irons Production Based on Strain Hardening Analysis

Angella

Zanardi

2019

Metals

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A mathematical procedure based on the analysis of tensile flow curves has been proposed to assess the microstructure quality of several ductile irons (DIs). The procedure consists of a first diagram for the assessment of the ideal microstructure of DIs, that is, the matrix where mobile dislocations move, and a second diagram for the assessment of the casting integrity because of potential metallurgical discontinuities and defects in DIs. Both diagrams are based on the dislocation-density-related constitutive Voce equation that is used for modeling the tensile plastic behavior of DIs. The procedure stands on the fundamental assumption that the strain hardening behavior of DIs is not affected by the nature and the density of the potential metallurgical discontinuities and defects, which are expected to affect only the elongations to fracture. However, this fundamental assumption is not obvious, and so its validity was evaluated through tensile testing Isothermed Ductile Irons (IDIs) 800, showing a wide scatter of elongations to rupture. The analysis of the strain hardening behaviors supported by strain energy density calculations of IDIs tensile tests proved that the fundamental assumption was valid and the quality assessment procedure could be applied to IDIs. A modified Voce equation was also introduced to improve the fitting of the experimental tensile flow curves and the strain energy density calculations.

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“…In order to do so, a material containing mainly 3.10 wt.% C, 4.45 wt.% Si and also 0.0037 wt.% Sb (balance Fe) was selected. Before casting, the melt was treated for graphite spheroidization and inoculated as described previously [7]. Metallographic observation showed a fully ferritic matrix in the as-cast state, with an even distribution of graphite spheroids as seen in figure 1-a.…”

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Coarsening and dendritic instability of spheroidal graphite in high silicon cast iron under thermal cycling in the ferritic domain

et al. 2020

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High silicon ferritic spheroidal graphite cast irons have been developed for high temperature service, in particular under thermal cycling conditions. The theoretical maximum service temperature is defined as the upper limit of the two-phase ferrite+graphite domain, which increases with the alloy silicon content. While isothermal heat treatment close to this temperature showed little evolution of the graphite distribution, thermal cycling led to a significant coarsening of the graphite particles associated with dendritic overgrowth of the large graphite particles. This unexpected behaviour is here observed and described for the first time.

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Effects of high silicon contents on graphite morphology and room temperature mechanical properties of as-cast ferritic ductile cast irons. Part I – Microstructure

Abstract: Effects of high silicon contents on graphite morphology and room temperature mechanical properties of as-cast ferritic ductile cast irons.

Cited by 34 publications

References 15 publications

Some paradoxical observations about spheroidal graphite degeneracy

Some paradoxical observations about spheroidal graphite degeneracy

Validation of a New Quality Assessment Procedure for Ductile Irons Production Based on Strain Hardening Analysis

Coarsening and dendritic instability of spheroidal graphite in high silicon cast iron under thermal cycling in the ferritic domain

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