The Role of Compounds in Graphite Formation in Cast Iron - A Review

Riposan, Iulian; Chişamera, Mihai; Stan, Stelian

doi:10.4028/www.scientific.net/msf.925.3

Cited by 14 publications

(28 citation statements)

References 25 publications

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“…The occurrence of nucleation substrates in the form of oxides, nitrides, or sulfides is perfectly described in the studies conducted by Riposan, who analyzed the crystallization of graphite inclusions in grey cast iron [ 23 , 24 ]. Observing the analysis performed by Riposan (see Figure 7 ) allows us to find similarities to the investigations performed herein.…”

Section: Resultsmentioning

confidence: 99%

Bifilm Defects in Ti-Inoculated Chromium White Cast Iron

Dojka

Stawarz

2020

Materials

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In recent years, white chromium cast iron has gained a well-settled position among wear-resistant materials. In recent times, chromium cast iron samples containing titanium have attracted attention. In cast iron samples, titanium combines with carbon and forms TiC particles, which may be form a crystallization underlay for eutectic M7C3 carbides and austenite. Accordingly, the inoculation process occurring in the crystallizing alloy should result in the proper, regular distribution of fine eutectic chromium carbides in the austenitic matrix. The presented research was conducted on 20% Cr hypoeutectic white cast iron with the addition of 0.5, 1, and 2% of Ti. Ti inoculation and the presence of TiC allowed for superior wear properties to be obtained. However, the conducted study revealed a significant decrease in the impact strength of examined alloys, especially for the cast iron samples with a high amount of Ti, in which the TiC compounds agglomerated. Titanium compounds accumulate in clusters and their distribution is irregular. Most of the TiC compounds were transported by the crystallization front into the center of the castings, where micropores were formed, meaning they were no longer effective crystallization underlays. In the authors’ opinion, the agglomerate formation is strictly connected with the appearance of bifilm defects in the casting microstructure. The conducted research shows how an incorrect volume of an additive may have negative influences on the properties of the casting. This is a vital issue not only from a technological point of view, but also for economic reasons.

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Section: Resultsmentioning

confidence: 99%

Bifilm Defects in Ti-Inoculated Chromium White Cast Iron

Dojka

Stawarz

2020

Materials

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“…At the usual manganese content levels (0.67-0.70%Mn), this cast iron contains a low sulphur content (<0.03%S), which is typical for electrical melting. As a result, the control factor (%Mn) × (%S) <0.02, based on complex (Mn,X)S compound formation, which showed difficult conditions for heterogeneous graphite nucleation [31], was found to comprise the major graphite nucleation sites in commercial grey cast iron [2,3,[6][7][8][9][10][11][12][13][14][15][16][17]. The very low content of Al, Zr and Ti, also typical for acid lined, coreless induction furnace melting [2], does not support the complex manganese-sulphite formation, especially at lower sulphur content levels.…”

Section: Chemical Compositionmentioning

confidence: 99%

“…Graphite nucleates on the sides of the (Mn,X)S compounds because of the low crystallographic misfit with graphite [7][8][9]. The role of complex (Mn,X)S sulphides in graphite formation in commercial grey cast irons is also sustained by other representative research works [10][11][12][13][14][15].…”

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confidence: 99%

Ce-Bearing FeSi Alloy Inoculation of Electrically Melted, Low Sulphur Grey Cast Irons for Thin Wall Castings

Balkan

Riposan

2021

Metals

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Electrically melted and over-heated (>1500 °C) grey cast iron at less than 0.04%S, as commonly used, solidifies large amounts of carbides and/or undercooled graphite, especially in thin wall castings; this is necessary to achieve a stronger inoculation. The efficiency of Ce-bearing FeSi alloy is tested for lower ladle addition rates (0.15 and 0.25 wt.%), compared to the base and conventional inoculated iron (Ba,Ca-bearing FeSi alloy). The present work explores chill and associated structures in hypoeutectic grey iron (3.6–3.8%CE, 0.02%S, (%Mn) × (%S) = 0.013–0.016, Alres < 0.002%), in wedge castings W1, W2 and W3 (ASTM A 367, furan resin sand mould), at a lower cooling modulus (1.1–3.5 mm) that is typically used to control the quality of thin wall iron castings. Relatively clear and total chill well correlated with the standard thermal (cooling curve) analysis parameters and structural characteristics in wedge castings, at different wall thickness, displayed as the carbides/graphite ratio and presence of undercooled graphite morphologies. The difference in effects of the two inoculants addition is seen as the ability to decrease the amount of carbides and undercooled graphite, with Ce-bearing FeSi alloy outperforming the conventional inoculant, especially as the wall thickness decreased. It appears that Ce-bearing FeSi alloy could be a solution for low sulphur, electric melt, thin wall iron castings production.

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“…Nodulization in cast irons is a process of controlling the structure and properties by changing the graphite shape from flakes to spheroidal, during the solidification process [1][2][3][4][5][6]. The nodularizers are added into the liquid iron to promote the formation of spheroidal (or compacted) form of graphite, specific for the ductile irons.…”

Section: Introductionmentioning

confidence: 99%

“…The nodularizers are added into the liquid iron to promote the formation of spheroidal (or compacted) form of graphite, specific for the ductile irons. Therefore, a certain quantity of nodularizing agent is necessary to obtain the spheroidal (or compacted) form of graphite [1][2][3][4][5][6][7][8][9]. So, production of ductile iron with consistent properties is generally accomplished by the addition of nodulizing elements in the iron alloys [1][2][3][4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Constructive Improvements in the In-Ladle Treatments

Kiss¹

2022

Teh. glas. (Online)

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Nodular gray cast iron having properties superior to conventional gray cast iron can be produced by treating the molten iron so that, when cast, the graphite will be compacted rather than in flake form. One such treatment involves the introduction of magnesium (Mg) into a molten iron bath of such composition. It is the principal object of the present industrial experiments to provide an improved process for the ductile cast iron production. Another object is to provide a process which permits the efficient use of the nodulizing agents, which results in the efficient production of an improved homogeneous nodular cast iron. Essentially such treatments result in the retention by the cast iron of small amounts of nodulizing agents, for example magnesium (Mg). Conventionally these agents are added to cast iron, usually in the form of pre-alloys and the efficiency of the process is illustrated by the high assimilation of the added nodulizer’s constituents. Another object of this technological practice is to provide an improved method for introducing the nodulizing agents, using constructive improvements to the in-ladle equipment. Finding magnesium (Mg) using novel techniques is the first step to advance the understanding of the role of magnesium (Mg) in the formation of the nodular graphite, the mechanism behind nodular graphite formation due to the addition of Magnesium (Mg) being still relative unclear at present time. Moreover, this may advance new methods to improve the nodulizing treatment process. This study take into account the flexibility of the used technique, which describes the elasticity of the treatment process, by improvement or alternative to the existing one. As nodulizing agents magnesium-ferrosilicon (Fe-Si-Mg type) and cerium-magnesium-ferrosilicon (Nodulin type) are examples of materials containing nodulizing agents that have given excellent results in the mixture. This experiments relates to a process for the production of ductile iron (nodular gray cast iron) and particularly to a process for adding magnesium (Mg) to the melted iron.

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The Role of Compounds in Graphite Formation in Cast Iron - A Review

Cited by 14 publications

References 25 publications

Bifilm Defects in Ti-Inoculated Chromium White Cast Iron

Bifilm Defects in Ti-Inoculated Chromium White Cast Iron

Ce-Bearing FeSi Alloy Inoculation of Electrically Melted, Low Sulphur Grey Cast Irons for Thin Wall Castings

Constructive Improvements in the In-Ladle Treatments

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