Chunky Graphite in Ferritic Spheroidal Graphite Cast Iron: Formation, Prevention, Characterization, Impact on Properties: An Overview

Baer, Wolfram

doi:10.1007/s40962-019-00363-8

Cited by 35 publications

(21 citation statements)

References 58 publications

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“…Possible reasons are long solidification times, high amounts of Si and the presence of Ce in the melt. 1 According to References 2-4, small amounts of Pb, Bi or Sb in a defined stoichiometric ratio with Ce can neutralize the detrimental effects of Ce on graphite growth by forming intermetallic phases in the melt. That is why mainly in large ductile iron castings very small amounts of Sb between 20 and 40 ppm are added to the cast iron melt to avoid the formation of chunky graphite.…”

Section: Introductionmentioning

confidence: 99%

Effect of Antimony on Graphite Growth in Ductile Iron

2020

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Antimony is used in ductile cast iron melts to avoid graphite degenerations like exploded graphite and chunky graphite. However, the effect of Sb in the melt on the crystallization of ductile cast iron is still unknown, therefore the aim of our investigations. The current study presents thermodynamic calculations showing that at the beginning of the eutectic solidification, Mg 3 Sb 2 is formed. Furthermore, the amount of Sb increases in the austenite and decreases in the remaining melt during solidification. An experiment was conducted, in which a higher amount of Sb than usual was added to a ductile iron melt. In the microstructure of the Sb-containing sample, a higher graphite precipitate count was measured than in the reference sample without Sb. The graphite spheroids of the Sb-containing sample show an almost perfect roundness and a very smooth surface. However, lamellar outgrowths from the graphite spheroids were also observed. Using scanning electron microscopy with energy-dispersive X-ray spectroscopy, it could be shown that Sb-containing phases have been formed, which are located in the pearlitic matrix and also in graphite spheroids. As a result of spectroscopic investigations, it can be assumed that Sb-containing phases act as nucleant for graphite nucleation. Further investigations by Auger electron spectroscopy showed that a thin layer of Sb at the interface between graphite and matrix has been formed. It seems that this layer constricts the diffusion of carbon to the spheroidal graphite and acts as a surfactant favoring a layer-by-layer growth of the graphite spheroids.

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Section: Introductionmentioning

confidence: 99%

Effect of Antimony on Graphite Growth in Ductile Iron

2020

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“…There are many forms of so-called degenerated graphite, including dendritic, exploded, chunky, and spiky. They all have damaging effects on the mechanical properties of the iron, as summarized in an excellent review for chunky graphite (CHG) by Baer [13].…”

Section: Growth Of Spheroidal Graphitementioning

confidence: 99%

“…This trend is the result of the continuous progress in understanding the processing -structureproperties paradigm of ductile iron, to include its solidification and its subsequent solid-state transformation during cooling or heat treatment. Review work on the solidification of cast iron has been periodically published, [6][7][8][9], with some addressing nucleation [10,11], while others focus on growth [12,13]. We also note Prof. Campbell's work [14] that will be discussed in more detail later in this paper.…”

Section: Introductionmentioning

confidence: 99%

“…Maximum tolerable Si content to avoid chunky graphite, Si is in mass%, and the elements on the abscissa are in ppm, 3.40% ≤ C ≤ 3.77%, reproduced from[13,141] with permission from Springer.…”

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confidence: 99%

“…Influence of element ratio parameter on the risk of chunky graphite formation in SG iron, M-thermal modulus, 3.47% ≤ C ≤ 3.75%, reproduced from[13,142] with permission from Springer.…”

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confidence: 99%

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Recent Developments in Understanding Nucleation and Crystallization of Spheroidal Graphite in Iron-Carbon-Silicon Alloys

Stefanescu

Alonso

Súarez

2020

Metals

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The last decade has witnessed significant research efforts directed to the understanding of nucleation and crystallization of graphite and associated solidification phenomena, driven in part by the ever-growing interest in the use of spheroidal graphite cast iron in the manufacture of large castings, such as wind turbine parts. These applications raised new challenges to the production of sound castings, mostly because of the exceedingly long solidification times imposed by the size of the castings. These solidification conditions resulted in many instances in graphite degeneration with subsequent decrease in mechanical properties. Obviously, the subject of graphite nucleation and crystallization in cast iron is still in need of additional answers. Over the years, many reviews of the subject have been published. The goal of this paper is to provide an update on the advances achieved in comprehending the mechanisms that govern the nucleation and crystallization of spheroidal graphite and related imperfect morphologies from iron-carbon-silicon melts. In this analysis, we examine not only the crystallization of graphite in cast iron, but also that of metamorphic graphite (natural graphite formed through transformation by heat, pressure, or other natural actions), and of other materials with similar lattice structure and crystallization morphologies.

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Surface Functionalization of Novel Work‐Hardening Multi‐Principal‐Element Alloys by Ultrasonic Assisted Milling

Preuß,

Lindner,

Hanisch

et al. 2024

Adv Eng Mater

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The development of multi‐principal‐element alloys (MPEAs) with unique characteristics such as high work hardening capacity similar to well‐known alloy systems like Hadfield steel X120Mn12 (ASTM A128) is a promising approach. Hence, by exploiting the core effects of MPEAs, the application range of conventional alloy systems can be extended. In the present study, work‐hardening MPEAs based on the equimolar composition CoFeNi are developed. Mn and C are alloyed in the same ratio as for X120Mn12. The production route consists of cast manufacturing by an electric arc furnace and surface functionalization via mechanical finishing using ultrasonic‐assisted milling (USAM) to initiate work hardening. The microstructure evolution, the hardness as well as the resulting oscillating wear resistance are detected. A pronounced lattice strain and grain refinement due to the plastic deformation during the USAM is recorded for the MPEA CoFeNi‐Mn12C1.2. Consequently, hardness increases by ≈380 HV0.025 in combination with a higher oscillating wear resistance compared to the X120Mn12. This shows the promising approach for developing work‐hardening alloys based on novel alloy concepts such as MPEAs.

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Chunky Graphite in Ferritic Spheroidal Graphite Cast Iron: Formation, Prevention, Characterization, Impact on Properties: An Overview

Cited by 35 publications

References 58 publications

Effect of Antimony on Graphite Growth in Ductile Iron

Effect of Antimony on Graphite Growth in Ductile Iron

Recent Developments in Understanding Nucleation and Crystallization of Spheroidal Graphite in Iron-Carbon-Silicon Alloys

Surface Functionalization of Novel Work‐Hardening Multi‐Principal‐Element Alloys by Ultrasonic Assisted Milling

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