Effect of Bismuth on Preventing Chunky Graphite in High-Silicon Ductile Iron Castings

Bauer, Branko; Pokopec, Ivana Mihalic; Petrič, Mitja; Mrvar, Primož

doi:10.1007/s40962-020-00419-0

Cited by 6 publications

(2 citation statements)

References 11 publications

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“…Adding a small amount of magnesium can change graphite from a lamellar shape to discrete graphite spheroids with an associated marked increase in mechanical properties (Doru, 2017). Recent research by Bauer et al, (2020aBauer et al, ( , 2020b has indicated that adding bismuth and changing the cooling rate can also change the graphite shape. However, elimination of graphite to improve the corrosion resistance of high silicon iron-based alloys has not previously been described in similar studies.…”

Section: Introductionmentioning

confidence: 99%

Effect of electrolysis parameters on corrosion resistance of extra-low carbon high silicon iron-based alloy

Zhang

Xiao

Yang

et al. 2021

ACMM

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Purpose High silicon iron-based alloys possess excellent corrosion resistance in certain specific media, but the effects of electrolysis parameters on corrosion resistance remain unknown. This study aims to guide the development and application of an extra-low carbon high silicon iron-based alloy (ECHSIA) in electrode plates. Design/methodology/approach The corrosion resistance of ECHSIA and a conventional high-silicon cast iron (CHSCI) was analyzed through experimental characterizations. The morphology was observed by scanning electron microscopy. The influence of electrolysis parameters on the corrosion resistance of ECHSIA was investigated through corrosion experiments. The relationship between the electrolysis parameters and the corrosion resistance of ECHSIA was statistically investigated using the grey correlation analysis method. Findings The corrosion resistance of the ECHSIA is better than that of the CHSCI. The corrosion rate showed an increasing tendency with the increase in the nitric acid concentration (CHNO3), electrolyte temperature and current density. The grey correlation analysis results showed that the CHNO3 was the main factor affecting the corrosion rate of the ECHSIA. Originality/value An ECHSIA with a single ferrite microstructure was prepared. This study provides a guideline for the future development and application of ECHSIAs as electrode plates.

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Section: Introductionmentioning

confidence: 99%

Effect of electrolysis parameters on corrosion resistance of extra-low carbon high silicon iron-based alloy

Zhang

Xiao

Yang

et al. 2021

ACMM

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“…Although the effect of silicon on the formation of chunky graphite has long been documented [15,19,[28][29][30], much less is known about its appearance in the high-silicon spheroidal graphite cast irons that are currently under development [26,31]. Such an interest is also triggered by the fact that it has been demonstrated that chunky graphite does not affect room temperature mechanical properties of high-silicon spheroidal graphite cast irons contrary to the case of low-silicon alloys [32].…”

Section: Introductionmentioning

confidence: 99%

Chunky Graphite in Low and High Silicon Spheroidal Graphite Cast Irons–Occurrence, Control and Effect on Mechanical Properties

et al. 2020

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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 unexpectedly, controlled rare earths contents appear beneficial for decreasing chunky graphite when using standard charge materials. Tin is shown to decrease chunky graphite appearance and it is evidenced that this effect is not related to rare earths. Finally, the effect of tin and antimony are compared and it is noticed that both suppress chunky graphite but also lead to some spiky graphite when no rare earth is added. Chunky graphite negatively affects the room temperature mechanical properties, though much more in the case of low silicon spheroidal graphite cast irons than in high silicon ones. Spiky graphite has been found to be much more detrimental and should thus be avoided.

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Alteration of the Graphite Morphology in Solid Solution-Strengthened Ductile Iron Due to High Contents of Cerium and Bismuth

Stieler

Funk²,

Tonn

2022

Inter Metalcast

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The impact of combined addition of high levels of bismuth up to 120 wt ppm and cerium up to 2000 wt ppm on the graphite morphology in GJS 450-18 with 3.2 wt% carbon and 3.2 wt% silicon was studied. Experiments were conducted with insulated keel blocks with a solidification time of 40 min. Samples from the thermal centre of the castings were analysed by optical microscopy, and the forms and sizes of graphite particles were characterised. Bismuth addition, even at 25 wt ppm, resulted in an altered graphite form in the last-to-freeze regions resembling intercellular lamellar graphite (ILG). Additions of 45 wt ppm or more Ce to these Bi-containing melts prevented the formation of ILG and produced chunky graphite (CHG) instead. ILG did not appear for ratios Bi/Ce > 1.5, while CHG could not be found for ratios Bi/Ce < 0.7. Only one type of graphite degeneration (either ILG or CHG) was present in each sample, thus rendering their formation mutually exclusive. Larger amounts of Ce between 300 and 500 wt ppm resulted in the formation of predominantly graphite form V, while no degenerations could be observed. The addition of Ce to a Bi-contaminated cast iron melt to avoid ILG formation and achieve a regular graphite structure with mainly form VI graphite is not possible. Instead, form V replaces form VI as the predominantly formed morphology. Ce levels higher than 1000 wt ppm resulted in the formation of large areas of undercooled graphite in the last-to-freeze regions regardless of the Bi content in the cast iron melt.

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Effect of Bismuth on Preventing Chunky Graphite in High-Silicon Ductile Iron Castings

Cited by 6 publications

References 11 publications

Effect of electrolysis parameters on corrosion resistance of extra-low carbon high silicon iron-based alloy

Effect of electrolysis parameters on corrosion resistance of extra-low carbon high silicon iron-based alloy

Chunky Graphite in Low and High Silicon Spheroidal Graphite Cast Irons–Occurrence, Control and Effect on Mechanical Properties

Alteration of the Graphite Morphology in Solid Solution-Strengthened Ductile Iron Due to High Contents of Cerium and Bismuth

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