Reexamination of crystal growth theory of graphite in iron-carbon alloys

Stefanescu, Doru M.; Alonso, G.; Larrañaga, P.; Fuente, E. de la; Súarez, Ramón

doi:10.1016/j.actamat.2017.08.004

Cited by 48 publications

(31 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…As the solidification progresses, the plates thicken to form successive layers. They developed this theory in their work [15], proving that these plates are built according to various mechanisms: tile, curved-circumferential, spiral, and pyramidal or conical. Stefanescu D.M.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

The Importance of SiC in the Process of Melting Ductile Iron with a Variable Content of Charge Materials

Janerka

Kostrzewski²,

Stawarz

et al. 2020

Materials

View full text Add to dashboard Cite

The article presents issues related to melting ductile iron grade EN-GJS-400-15, with different proportions of feedstock (steel scrap and pig iron). The main attention was paid to determining the impact of silicon carbide on the structure and properties of melted cast iron. In the conducted melts, carbon and silicon deficiencies were supplemented with a suitably chosen carburizer, ferrosilicon, and SiC metallurgical silicon carbide. The percentage of silicon carbide in the charge ranged from 0 to 0.91%. The basic condition for the planning of melts was to maintain the repeatability of the chemical composition of the output cast iron and cast iron after the secondary treatment of liquid metal with various charge compositions. Based on the tests, calculations, and analyses of the results obtained, it was concluded that the addition of SiC may increase the number and size of graphite precipitates. Increasing the SiC content in the charge also caused a change in the solidification nature of the alloy and the mechanism of growth of spheroidal graphite precipitates, causing their surface to form a scaly shell. The influence of the addition of silicon carbide on the reduction of the temperature of liquidus in the alloys was also observed. Silicon carbide had a positive effect on the structure and properties of melted alloys. The introduction of SiC into the melting in the studied range caused an increase in the content of carbon and silicon without causing an increase in the amount of impurities in the alloy.

show abstract

Section: Resultsmentioning

confidence: 99%

“…Stefanescu D.M. et al stated that the final shape of graphite spheroids is influenced by nuclear crystallography because it determines the initial growth of graphite plates [15].…”

Section: Resultsmentioning

confidence: 99%

The Importance of SiC in the Process of Melting Ductile Iron with a Variable Content of Charge Materials

Janerka

Kostrzewski²,

Stawarz

et al. 2020

Materials

View full text Add to dashboard Cite

show abstract

“…According to Stefanescu et al, 8 the carbon precipitating as graphite nodules during stable eutectic solidification is rapidly surrounded by a closed austenitic halo due to carbon depletion in the vicinity of the nuclei. As the solidification progresses, decoupled growth takes place, since the graphite is not in direct contact with the remaining liquid.…”

Section: Introductionmentioning

confidence: 99%

Application of Surface Layer Inoculation Processes to Solid Solution-Strengthened Ductile Cast Iron

Franzen

Weiss

Gundlach³

et al. 2020

Inter Metalcast

View full text Add to dashboard Cite

Within the present investigations, an in-mould inoculation method for ductile cast iron with elevated silicon contents was developed. The inoculation process takes place at the interface between the mould's surface and the melt. The application of a mould wall inoculation process allows inoculation at the latest possible point in time, which means high efficiency due to reduced fading effects. For this purpose, various inoculant suspensions are produced, containing inoculants in different amounts and grain fractions. The inoculant is applied to the surface of a PEP SET TM-bonded moulding material by means of an airpressurized spraying pistol. The specimen geometry used in the tests is a 5-stepped wedge, which represents wall thicknesses in the range of 5-40 mm. For a total of 8 castings, inoculant fractions in the spectrum of 0-25 and 0-45 lm are used to produce the solid solution-strengthened grade EN-GJS-500-14 that is specified in the European standard EN 1563. Metallographic investigations show that a complete solidification according to the stable system can be adjusted in the investigated wall thicknesses by inoculation with grain fractions of 0-25 lm.

show abstract

“…Understanding growth of spheroidal graphite remains a challenge for both geol og ists [1] and metallurgists [2]. As a matter of fact, graphite spheroids present structural characteristics which are unique and are definitely not tackled by simulation at meso scale such as phase field approach, see e.g.…”

Section: Introductionmentioning

confidence: 99%

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

2019

View full text Add to dashboard Cite

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 ...

show abstract

Reexamination of crystal growth theory of graphite in iron-carbon alloys

Cited by 48 publications

References 28 publications

The Importance of SiC in the Process of Melting Ductile Iron with a Variable Content of Charge Materials

The Importance of SiC in the Process of Melting Ductile Iron with a Variable Content of Charge Materials

Application of Surface Layer Inoculation Processes to Solid Solution-Strengthened Ductile Cast Iron

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

Contact Info

Product

Resources

About