Role of Lanthanum in Graphite Nucleation in Grey Cast Iron

Riposan, Iulian; Chişamera, Mihai; Stan, Stelian; Stefan, Elena; Hartung, Cathrine

doi:10.4028/www.scientific.net/kem.457.19

Cited by 18 publications

(15 citation statements)

References 9 publications

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“…5). 16) Mn and S were found as the basic components of all micro-inclusions found in commercial irons, regardless of their position in the iron structure, iron chemistry, or iron melt treatment. In all of the above conditions manganese sulphides were a complex rather than the simple type.…”

Section: )mentioning

confidence: 99%

Enhanced Quality in Electric Melt Grey Cast Irons

2013

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The paper reviews original data obtained by the authors, recently disconnected published, concerning the specific solidification pattern of low S (<0.05%) irons, with very low Al (<0.005%), melted and superheated in acid lined, coreless induction furnaces, and how superheating affects the iron quality with effective metallurgical treatments for use in these conditions. Solidification undercooling increased with increasing superheat, associated with significant changes in chemical composition, such as C, Si, Mn, Al and Zr, involved in the nucleation of graphite. The concept in the present paper sustains a three-stage model for nucleating flake graphite [(Mn,X)S type nuclei]. There are three important groups of elements [deoxidizer/ Mn, S/inoculating] and three technology stages in electric melt iron [superheat/pre-conditioning base iron/ final inoculation]. Different materials were used for pre-treatment of the iron melt, to control oxidization levels and/or to promote active graphite nucleation sites, including carbon materials and metallurgical silicon carbide. Special attention was paid to maintain Al and Zr recoveries in the melting furnace for their effects on the iron structure. A double treatment utilizing strong oxide forming elements, such as Al and Zr for preconditioning, followed by inoculation decreased eutectic undercooling parameters. This treatment improved graphite characteristics and avoided carbides. For foundry application, it is recommended to ensure (Mn,X)S compound formation, compatible for nucleating graphite with less eutectic undercooling. Attention is drawn to ensuring a control factor (%Mn) × (%S) equals 0.03 -0.06, accompanied by 0.005-0.010% Al and/or Zr content in inoculated grey irons.

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Section: )mentioning

confidence: 99%

Enhanced Quality in Electric Melt Grey Cast Irons

2013

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“…Similarly, the inoculation elements have a strong affinity to oxygen and sulfur [8][9][10][11] . Thus, oxides and sulphides of a homogeneous or heterogeneous nature formed in the melt give the graphite nucleation sites [12][13][14] . Some authors suggested that the Mn/S ratio affects the nucleation and morphology of graphite [15,16] .…”

Section: Introductionmentioning

confidence: 99%

Niobium addition effect in molds at last cooling step on EN-GJL250 gray cast iron: Microstructural changes and electrochemical behavior

et al. 2018

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I t is well established that the variety of applications of cast iron is attributed to the presence of chemical elements in the solid solution as interstitial or substitutional form, such as so-called addition elements Ni, Cu, Ti, Cr, V and Nb [1][2][3][4] , and inoculation elements Al, Si, Ca, Sr, Mn, Zr, P, Sn and Ce [5][6][7] .In the foundry, additions are done by controlling the Abstract:The purpose of this study was to determine the impact of niobium addition as an inoculation element on the microstructure and electrochemical properties of EN-FGL250 gray cast iron. Niobium additions are in a powder form and have a 0.5 mm particle size at dfferent proportions of 1wt.% and 3wt.%. The addition was done during casting of the metal in the mold at the last cooling step of the melt cast iron. These additions have a significant impact on the phenomenon of solidification as the metal powder deposited in the sand molds creates new centers of germination and absorbs a lot of heat. The cooling rate directly affects the microstructure and electrochemical behavior. This is confirmed by SEM observations and electrochemical tests. Furthermore, the addition of niobium transforms the microstructure of gray cast iron from cellular structure into totally dendritic structure. As a consequence, the niobium addition affected the shape and size of graphite, thus considerably reducing the corrosion current density by increasing the polarization resistance R p . chemical composition of the melt rather than equivalent carbon, alloying elements and inoculation products. The minor additions of alloying elements for their affinities to carbon can be used to improve the mechanical properties of the cast iron mainly by the formation of M 7 C 3 , M 3 C and MC type carbides. Filipovic et al. [4] have shown that variable proportions of additions of niobium and vanadium to the hypoeutectic white cast iron containing 19% chromium modify its microstructure and affect its wear and hardness properties. Kesseri et al. [3] have also shown that the addition of niobium in chromium-rich cast irons improves the mechanical properties by the formation of MC-type niobium carbides. Similarly, the inoculation elements have a strong affinity to oxygen and sulfur [8][9][10][11] . Thus, oxides and sulphides of a homogeneous or heterogeneous nature formed in the melt give the graphite nucleation sites [12][13][14] . Some authors suggested that the Mn/S ratio affects the nucleation and morphology of graphite [15,16] . Other authors [17,18] indicated that the inoculations elements *M. O. Azzoug Male, born in 1979, Teacher (assistant master) at University of Sciences and Technology Houari Boumedienne Algiers, Algeria, also Ph.D student in Materials Science and Engineering. He is currently working on the development of a surface treatment process for gray cast irons directly in the manufacturing stage of parts without resorting to conventional (physical or chemical) surface treatments by metal deposition process or surface treatment. The influence of additions in ...

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“…[1][2][3][4][5][6][7][8][9][10] This unfavourable effect is caused by sulphur contained in a hardener of resin binders, which enters the surface layer causing degradation of a nodular graphite into flake graphite. In such case the degenerated surface layer can cause stress raising in the casting, similar to a notch, so all useful properties are reduced, especially the fatigue limit and impact resistance.…”

Section: Introductionmentioning

confidence: 99%

Effect of the Quality of Furan Moulding Sand on the Skin Layer of Ductile Iron Castings

et al. 2014

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The paper presents the results of investigations of the influence of the quality of moulding sand with furfuryl resin hardened by paratoluenosulphonic acid, on the formation of microstructure and surface quality of ductile iron castings. Within the studies different moulding sands were used: moulding sand prepared with fresh sand and moulding sands prepared with reclaimed sands of a different purification degree, determined by the ignition loss value. Various concentrations of sulphur and nitrogen in the sand moulds as a function of the ignition loss were shown in the paper as well as the gas emission and gas evaporation rate from the moulding sands. A series of experimental melts of ductile iron in moulds made of moulding sand characterized by different levels of surface-active elements (e.g. sulphur) and different gas evolution rates were performed. It was shown that there exist a significant effect of the quality of the sand on the formation of the graphite degeneration layer.

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Role of Lanthanum in Graphite Nucleation in Grey Cast Iron

Cited by 18 publications

References 9 publications

Enhanced Quality in Electric Melt Grey Cast Irons

Enhanced Quality in Electric Melt Grey Cast Irons

Niobium addition effect in molds at last cooling step on EN-GJL250 gray cast iron: Microstructural changes and electrochemical behavior

Effect of the Quality of Furan Moulding Sand on the Skin Layer of Ductile Iron Castings

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