Comparative Study of Fatigue Endurance Limit for 4 and 6 mm Thin Wall Ductile Iron Castings

Labrecque, C.; Gagné, M.; Pierre-Marie, Cabanne; François, Camille; Becret, C.; Hoffmann, Fabian

doi:10.1007/bf03355424

Cited by 17 publications

(12 citation statements)

References 2 publications

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“…The effect of casting skin on mechanical properties has been documented in the literature. A clear reduction in tensile and yield strength that occur in both ductile and compacted graphite iron was shown [7,9,25,26].…”

Section: Graphite Degradation Mechanismsmentioning

confidence: 95%

The Influence of Mold/Metal Interactions on the Castings Microstructure—Bibliographical Research

Holtzer

2015

Microstructure and Properties of Ductile Iron and Compacted Graphite Iron Castings

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The phenomena on the mold/metal interface largely determine the microstructure of the casting surface layer, quality of the surface and casting performance characteristics (mechanical properties, wear resistance, corrosion resistance, etc.). Processes that occur here are of particular importance in the case of cast iron with vermicular or spheroidal graphite performed in sand molds (graphite degradation and graphite depletion). It is assumed that the direct cause of graphite degradation, resulting in a layer of flake graphite, is the Mg depletion at the surface layer of the casting and the main reason (although not the only) for the decrease of the Mg concentration is the reaction of sulfur and oxygen. To explain this phenomenon, Fe-Mg, Mg-S, Mg-O and Fe-S systems have been discussed. Performed thermodynamic calculations have shown that the magnesium and sulfur and oxygen reactions in liquid iron occur in the gas phase, wherein the thermodynamic reaction of Mg vapors with oxygen gas is more privileged than with the sulfur vapors. To clarify the mechanism of the formation of the surface layer on the casting Stefanescu et al. developed a thermo-diffusion model 2-D. However, this model does not take the kinetic agent and the degree of undercooling during solidification of the casting into account, which affects the amount of primary austenite formed, which may also result in a reduction of the Mg concentration. To reduce the degree of transition of sulfur from molding sand to casting surface layer, the use of protective coatings for molds and cores, containing desulfurization ingredients such as CaO, MgO, talc, or Mg-FeSi, which binds sulfur and supplements magnesium at the same time is preferred.The surface quality of castings is as important as its bulk properties. Surface quality is ultimately the product of physical and chemical interactions occurring between the molding material and the cast metal in liquid state as well as during solidification and subsequent cooling in the mold. The surface layer of a casting has, in most cases, a microstructure and associated properties that are different than those in the bulk of the casting. The casting surface exhibits some roughness, which commonly depends

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Section: Graphite Degradation Mechanismsmentioning

confidence: 95%

The Influence of Mold/Metal Interactions on the Castings Microstructure—Bibliographical Research

Holtzer

2015

Microstructure and Properties of Ductile Iron and Compacted Graphite Iron Castings

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“…Previous works [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] identified this type of surface degenerated structure as an effect of sulphur diffusion from the mould into the Mg-treated iron melt, consuming the nodulizing elements (Mg, Ce, La), before their action in the graphite spheroidization process. As a result, non-spheroidal graphite morphologies are formed, depending on the remanent content of these elements.…”

Section: Structure Characteristics In the Casting Surface Layermentioning

confidence: 99%

“…The degenerated graphite layer (skin) formation at the surface of the Mg-treated iron castings is generally accepted to be produced by chemical reactions between nodulizing elements from the iron melt (Mg, Ce, La) and active elements supplied by mould and core materials (sulphur, oxygen, nitrogen, moisture), mould and core coatings, and gaseous atmosphere in the mould cavity [6][7][8][9][10][11][12][13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Control of the Mg-Treated Iron Casting Skin Formation by S-Diffusion Blocking at the Metal–Mould Interface

et al. 2020

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Having established that sulphur presence in the mould materials appears to have an important contribution in graphite degeneration at least in the casting surface layer, a research program is undertaken to explore the possible beneficial effect of sulphur diffusion blocking at the metal–mould interface. Test samples, with and without a thin steel sheet (up to 3 mm thickness) application on the inner surface of the mould cavity, before iron melt pouring, are considered for structure analysis. A higher nodulizing potential (0.048% Mgres, 0.015% Ceres, and 0.006% Lares) decreases the occurrence of surface graphite degeneration in castings obtained in rigid chemically bonded resin sand moulds, using P-toluol sulfonic acid (PTSA) hardener (S-including), but it is not enough to avoid this phenomenon (200–400 μm skin in present experimental conditions). The casting skin appears to have different values, depending on the evaluation technique (un- and Nital-etching direct measurement, or graphite parameters variation on the casting section). In the presence of a thin steel sheet at the metal–mould interface, the casting skin thickness decreases or is just excluded. It is supposed that it acts as a barrier, blocking S-diffusion from the mould media into the iron melt. Without this S-diffusion, the graphite degeneration in the casting surface layer could be avoided, or at least diminished. For industrial application, the increasing of residual content of nodulizing elements is a limited solution, and it is recommended to use barriers to block S transfer on the mould/metal surface, such as dense coatings or coatings with desulphurization capacity.

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“…Although the graphite degeneration phenomenon was highlighted in the first iron castings, with compact graphite shapes obtained, not enough is known about the phenomenon at present. Many papers have identified its surface degenerated structure as an effect of sulfur diffusion from the mold into the Mg-treated iron melt [1][2][3][4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study Regarding the Possibility of Blocking the Diffusion of Sulfur at Casting-Mold Interface in Ductile Iron Castings

et al. 2021

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The main objective of this work is to investigate the mechanism of sulfur diffusion from the mold (sand resin P-toluol sulfonic acid mold, sulfur-containing acid) in liquid cast iron in order to limit the graphite degeneration in the surface layer of iron castings. A pyramid trunk with square section samples was cast. On the opposite side of the feed canal of the samples, steel sheets with different thicknesses (0.5, 1, and 3 mm) were inserted with the intention of blocking the diffusion of sulfur from the mold into the cast sample during solidification. The structure evaluation (graphite and matrix) in the surface layer and the casting body was recorded. The experimental results revealed that by blocking the direct diffusion of sulfur at the mold-casting interface, a decrease of the demodified layer thickness (for 0.5 mm steel sheet thickness) is obtained until its disappearance (for steel sheet thicknesses of more than 1 mm). The paper contains data that may be useful in elucidating the mechanism of graphite degeneration in the superficial layer of ductile iron castings. Based on the obtained results, we recommend using such barriers on the metal-mold interface, which are able to limit sulfur diffusion from the mold/core materials into the iron castings, in order to limit or even cease graphite degeneration in the Mg-treated surface iron casting layer. The paper presents additional data related to the interaction of sulfur at the ductile iron casting-mold interface previously analyzed.

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Comparative Study of Fatigue Endurance Limit for 4 and 6 mm Thin Wall Ductile Iron Castings

Cited by 17 publications

References 2 publications

The Influence of Mold/Metal Interactions on the Castings Microstructure—Bibliographical Research

The Influence of Mold/Metal Interactions on the Castings Microstructure—Bibliographical Research

Control of the Mg-Treated Iron Casting Skin Formation by S-Diffusion Blocking at the Metal–Mould Interface

Experimental Study Regarding the Possibility of Blocking the Diffusion of Sulfur at Casting-Mold Interface in Ductile Iron Castings

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