Relevant bibliographies by topics / Vacuum Arc Remelting (VAR)

Academic literature on the topic 'Vacuum Arc Remelting (VAR)'

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Published: 8 June 2024

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  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers

Journal articles on the topic "Vacuum Arc Remelting (VAR)":

1

Campbell, John. "A Future for Vacuum Arc Remelting and Electroslag Remelting—A Critical Perspective." Metals 13, no. 10 (September 23, 2023): 1634. http://dx.doi.org/10.3390/met13101634.

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In the secondary metals refining processes, vacuum arc remelting (VAR) and electroslag remelting (ESR), the consumable electrode is commonly produced by vacuum induction melting (VIM) which employs the regrettably primitive casting technique of simply pouring into the open top of the mold. Despite the vacuum, the resulting oxidizing conditions and the immensely powerful turbulence accompanying the top-pouring of the electrode is now known to create a substantial density of serious cracks. The cracks in the cast electrode are bifilms (double oxide films), which in turn are proposed to be responsible for the major faults of the VAR ingot, including undetectable, horizontal macroscopic cracks, white spots (clean and dirty varieties) and in-fallen crown. The remedial action to solve all these issues at a stroke is the provision of a counter-gravity cast electrode, cast in air or vacuum, or provision of any similar electrode substantially free from bifilm defects. The ESR process is also described, explaining the reasons for its significantly reduced sensitivity to the top-poured VIM electrode, but indicating that with an improved electrode, this already nearly reliable process has the potential for perfect reliability. The target of this critical overview is an assessment of the potential of these secondary refining processes to produce, for the first time, effectively defect-free metals, metals we can trust.
2

Mucsi, C. S., Rubens Nunes de Faria Jr., E. Galego, and J. L. Rossi. "Consolidation of Compacted Zircaloy Chips via Vacuum Arc Melting - Analysis of the Electric Arc." Materials Science Forum 498-499 (November 2005): 258–63. http://dx.doi.org/10.4028/www.scientific.net/msf.498-499.258.

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The main objective of this work is to present the preliminary results on the analysis of the signals arising from the electrical arc, during the vacuum arc remelting of Zircaloy electrodes, aiming the automation of the fusion process. Zircaloy electrodes were made from compacted chips resultant of the machining of Zircaloy rods. The melts were performed in a prototype (vacuum arc remelting) VAR furnace under low pressure of argon and the arc was fed by a constant DC power source. Both filtered and unfiltered signals were recorded by means of a data acquisition system. The fast Fourier transforms FFT and autocorrelation integral were used as tools for data analysis. The result showed that the events occurring within the electric arc have a strong influence on the electric signals. The analysis allowed inferring that the VAR electric arc system has mainly a chaotic behaviour and sporadic periods of linear behaviour. The conclusion of this work is that a control system may be developed, based on the modelling of the non-linear behaviour of the arc, mainly chaotic. This may allow the achievement of an automatic control for the process and yield better quality products.
3

Shi, Zhiyue, Wenquan Cao, Chengjia Shang, and Xiaodan Zhang. "Effect of inclusion type on the rotating bending fatigue properties of a high carbon chromium bearing steel." IOP Conference Series: Materials Science and Engineering 1249, no. 1 (July 1, 2022): 012032. http://dx.doi.org/10.1088/1757-899x/1249/1/012032.

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Abstract The use of the double vacuum melting route (conventional second refining + vacuum arc refining, CSR+VAR) and the electroslag remelting route (vacuum induction melting + electroslag remelting, VIM+ESR)) has been investigated for the SAE52100 (100Cr6) bearing steel. The tensile properties, impact toughness, hardness and RCF life of the CSR+VAR steel and the steel prepared using the VIM+ESR route are similar. The number and size of TiN inclusions in the VIM+ESR steel are higher and larger than those in the CSR+VAR steel, providing an explanation for the observation of better fatigue properties for the CSR+VAR steel. Two major types of inclusions, magnesium aluminates/Al2O3-CaO-CaS and TiN, are located in different areas in a map of stress intensity factor versus rotatory bending fatigue cycles (NRBF ). The negative impact of TiN inclusions on fatigue properties are greater than those of magnesium aluminates/Al2O3-CaO-CaS inclusions.
4

Alam, M. K., S. L. Semiatin, and Z. Ali. "Thermal Stress Development During Vacuum Arc Remelting and Permanent Mold Casting of Ingots." Journal of Manufacturing Science and Engineering 120, no. 4 (November 1, 1998): 755–63. http://dx.doi.org/10.1115/1.2830216.

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The development of thermal stresses in ingots during the vacuum arc remelting (VAR) as well as specialized permanent mold casting (PMC) process was modeled via numerical solution of the two-dimensional, nonsteady-state heat conduction and stress equilibrium equations. The numerical analysis was carried out in conjunction with experimental studies of the mechanical properties and microstructure of a cracked VAR titanium aluminide ingot. Numerical solutions were obtained for different values of ingot diameter, crucible-ingot interface heat transfer coefficients, and lengths of the melted-and-resolidified ingot. For both VAR and PMC, model predictions revealed that the maximum tensile thermal stresses are developed at the bottom of the ingot; the magnitude of such stresses increases with ingot diameter and the magnitude of the interface heat transfer coefficients. The microstructural analysis of a cracked ingot indicated that the thermal cracking occurred in the temperature range where the alloy has very little ductility. The predicted development of large tensile stresses correlates well with observations of thermal cracking during VAR of near-gamma titanium aluminide alloy ingots. By contrast, the predicted thermal stresses developed during PMC are lower, thus suggesting an attractive alternative to VAR to obtain sound, crack-free ingots.
5

Konopatsky, Anton S., Yulia S. Zhukova, and Mikhail R. Filonov. "Production and Quality Assessment of Superelastic Ti-Nb-Based Alloys for Medical Application." Advanced Materials Research 1040 (September 2014): 130–36. http://dx.doi.org/10.4028/www.scientific.net/amr.1040.130.

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Superelastic biocompatible metallic materials Ti-22Nb-6Zr and Ti-22Nb-3Ta-3Zr (at %) were produced. Vacuum arc remelting (VAR) with manual control allowed to produce high‑purity alloys. X-ray fluorescence spectrometry (XRF) results showed that one remelt was not enough to obtain homogeneous Ti-Nb-Ta-Zr ingot. Ti-Nb-Zr and Ti-Nb-Ta-Zr alloys were remelted 3 times and turned upside down after each remelting. Scanning electron microscopy (SEM) with micro X‑ray spectral analysis showed that chemical composition of the alloys coincided with nominal chemical composition. SEM results also showed that the alloys were mostly homogeneous. Recommendations for optimization of VAR in terms of producing high-purity homogeneous superelastic titanium alloys were elaborated.
6

Karimi-Sibaki, E., A. Kharicha, M. Wu, A. Ludwig, and J. Bohacek. "A Parametric Study of the Vacuum Arc Remelting (VAR) Process: Effects of Arc Radius, Side-Arcing, and Gas Cooling." Metallurgical and Materials Transactions B 51, no. 1 (October 29, 2019): 222–35. http://dx.doi.org/10.1007/s11663-019-01719-5.

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Abstract Main modeling challenges for vacuum arc remelting (VAR) are briefly highlighted concerning various involving phenomena during the process such as formation and movement of cathode spots on the surface of electrode, the vacuum plasma, side-arcing, the thermal radiation in the vacuum region, magnetohydrodynamics (MHD) in the molten pool, melting of the electrode, and solidification of the ingot. A numerical model is proposed to investigate the influence of several decisive parameters such as arc mode (diffusive or constricted), amount of side-arcing, and gas cooling of shrinkage gap at mold–ingot interface on the solidification behavior of a Titanium-based (Ti-6Al-4V) VAR ingot. The electromagnetic and thermal fields are solved in the entire system including the electrode, vacuum plasma, ingot, and mold. The flow field in the molten pool and the solidification pool profile are computed. The depth of molten pool decreases as the radius of arc increases. With the decreasing amount of side-arcing, the depth of the molten pool increases. Furthermore, gas cooling fairly improves the internal quality of ingot (shallow pool depth) without affecting hydrodynamics in the molten pool. Modeling results are validated against an experiment.
7

Descotes, Vincent, Thibault Quatravaux, Jean-Pierre Bellot, Sylvain Witzke, and Alain Jardy. "Titanium Nitride (TiN) Germination and Growth during Vacuum Arc Remelting of a Maraging Steel." Metals 10, no. 4 (April 22, 2020): 541. http://dx.doi.org/10.3390/met10040541.

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During the processing of maraging steels, Titanium easily combines with Nitrogen to form nitride inclusions, known to be deleterious for fatigue properties of the alloy. According to thermodynamic calculations, the precipitation occurs during solidification of the vacuum arc remelted (VAR) ingot. A coupled model of titanium nitride (TiN) inclusion precipitation and vacuum remelting has been set-up to study the inclusion cleanliness of the ingot. The nitrogen content, nuclei numeral density and solidification time appear as the key factors which control the inclusion size.
8

YUAN, LANG, GEORGI DJAMBAZOV, PETER D. LEE, and KOULIS PERICLEOUS. "MULTISCALE MODELING OF THE VACUUM ARC REMELTING PROCESS FOR THE PREDICTION ON MICROSTRUCTURE FORMATION." International Journal of Modern Physics B 23, no. 06n07 (March 20, 2009): 1584–90. http://dx.doi.org/10.1142/s0217979209061305.

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The final solidification structures of Vacuum Arc Remelting (VAR) ingots depend on the temperature distribution and fluid motion within the molten pool. In this paper, a three-dimensional multi-physics macroscale model for VAR is developed, based on the modular CFD software PHYSICA. This model is used to provide estimates of process parameters and to study complex physical phenomena, such as liquid metal flow with turbulence, heat transfer, solidification, and magnetohydrodynamics in the VAR process. The macromodel is coupled to a microscale solidification model. The micromodel combines stochastic nucleation and a modified decentred square/octahedron method to describe dendritic growth with a finite difference computation of solute diffusion. The resulting multiscale model allows prediction of the formation of microstructures in the solidifying mushy zone. This gives a better understanding of the whole VAR process from operational conditions to final ingot microstructures, as well as an essential first step in defect prediction.
9

Lv, Guo Yun, and Shui Xian Hu. "Research on Vacuum Consumable Arc Remelting Furnace Control System with Drop Short Pulses Testing." Advanced Materials Research 605-607 (December 2012): 1670–74. http://dx.doi.org/10.4028/www.scientific.net/amr.605-607.1670.

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Stable and Reliable automatic control system of Vacuum Consumable Arc Remelting (VAR) furnace is the key to smelt successfully special alloy metal and high temperature alloy metal, which is related to special properties of remelting ingot directly. This paper makes a deep study for drop short pulse testing and controlling system, and digital signal processing is used to obtain drop short pulse value with different frequency ranges. Firstly, basic theory analysis of drop short pulse measuring and controlling is researched. Secondly, high-speed digital signal processing technology is adopted to sample furnace voltage signal real-timely, band pass filter group is designed directly to process and calculate the amount of drop short pulses in different frequency ranges, Finally, the relationship between drop short pulse frequency and special alloy materials is analyzed, fuzzy PID control method is used to adjust electrode gap and control arc length. Field experiment results show the effectiveness of the whole drop short pulse testing and controlling system.
10

Geanta, Victor, Ionelia Voiculescu, Radu Stefanoiu, and Elena Roxana Rusu. "Stainless Steels with Biocompatible Properties for Medical Devices." Key Engineering Materials 583 (September 2013): 9–15. http://dx.doi.org/10.4028/www.scientific.net/kem.583.9.

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Stainless steels, commercial as well as with special properties, are the principal metallic materials used for medical devices manufacturing. Stainless steels for medical devices should have superior mechanical properties, as: hardness, wear resistance, tensile strength, elongation, fracture toughness, creep resistance etc. This paper aims to present experimental researches regarding the obtaining in vacuum arc remelting device (VAR) of austenitic and martensitic stainless steels and their characterization from microstructure and microhardness point of view.
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Journal articles Dissertations / Theses

Dissertations / Theses on the topic "Vacuum Arc Remelting (VAR)":

1

Polton, Richard. "Numerical grid generation and its application in the solution of a model of the Vacuum-Arc Remelting (VAR) process." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323918.

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2

Poullain, Thomas. "Etude numérique et expérimentale de l’évaporation sous vide d’alliages métalliques : application à la refusion VAR de Zircaloy-4." Electronic Thesis or Diss., Université de Lorraine, 2022. http://www.theses.fr/2022LORR0189.

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La maitrise de la composition et de la ségrégation chimique est essentielle lors de l’élaboration de matériaux à forte valeur ajoutée, comme les alliages de zirconium à destination de l’industrie nucléaire. L’élaboration sous vide permet d’obtenir des lingots d’une très grande pureté mais elle présente aussi une contrainte supplémentaire concernant la maitrise de la teneur en éléments d’alliage volatiles. Les travaux présentés dans ce document visent à améliorer la prédiction de la cinétique d’appauvrissement en espèces métalliques volatiles lors de l’élaboration sous vide et en particulier lors de la refusion VAR (Vacuum Arc Remelting ou refusion à l’arc sous vide) du Zircaloy-4, un alliage de Zr. Dans un premier temps, nous étudions la cinétique d’évaporation et l’expansion de la vapeur métallique produite lors de la fusion sous vide. L’étude est effectuée par une combinaison d’expériences en four à bombardement électronique et de la simulation numérique du comportement de la vapeur par une méthode particulaire (FPM). Nos études sur l’évaporation de métaux purs, Ti et Zr, montrent l’importance des collisions au-dessus du liquide sur l’expansion de la vapeur et sa recondensation. La caractérisation de l’expansion de la vapeur de Fe et Sn lors de la fusion sous vide de Zy4, combinée à la simulation particulaire, nous a permis de déterminer la valeur des coefficients d’activité thermodynamique de ces éléments dans le Zy4 liquide. Dans un second temps, nous présentons la simulation de l’expansion de la vapeur métallique dans les conditions du procédé VAR en nous intéressant particulièrement aux flux de condensation sur les différentes surfaces. L’application de ce modèle au Zircaloy-4 montre que la composition du dépôt sur la paroi interne de la lingotière est très différente de celle de l’alliage. Enfin, le modèle particulaire est couplé à une modélisation de la croissance du lingot et nous étudions l’influence de l’évaporation, condensation et réincorporation de la collerette sur la composition et la ségrégation des éléments d’alliage volatils. Le couplage offre aussi une première prédiction de l’épaisseur et de la composition de la collerette que nous comparons pour la refusion du Zyrcalloy-4 avec des prélèvements industriels
Composition and chemical segregation control is primordial when producing high value-added materials, such as zirconium alloys for nuclear industry. Vacuum processing allows production very high purity ingot, however it also presents an additional problematic concerning control and prediction of alloy elements evaporation. This PhD dissertation aims at improving prediction of volatile metallic species evaporation during vacuum elaboration, especially during Zircaloy 4 VAR (Vacuum Arc Remelting).First, the evaporation kinetics and the expansion of the metal vapour produced during vacuum melting is investigated. The study is done with a combination of volatilisation experiments using an experimental electron beam furnace and particle based numerical simulation (FPM) of vapour behaviour. Our volatilisation studies on pure metals, Ti and Zr, show the importance of collisions above the liquid on the vapour expansion and its recondensation. Determination of Fe and Sn vapour expansion during Zy4 vacuum melting combined with particle simulation, allowed us to determine thermodynamic activity coefficients values for these elements in liquid Zy4.Then, metallic vapour expansion under VAR conditions is studied, with particular interest shown to condensation flows on the different surfaces. Application of our numerical model to Zy4 shows that the vapour deposited on the mould has a very different composition compared to the alloy. Finally, the particle model is coupled to an ingot growth model and we study the influence of evaporation, condensation and crown reincorporation with regard to volatile solute segregation and depletion. This coupling also provides a first prediction of crown thickness and composition and we compare them to industrial crown samples
3

Ghazal, Ghassan. "Etude de la propreté inclusionnaire des lingots VAR - Application aux alliages de titane." Thesis, Vandoeuvre-les-Nancy, INPL, 2010. http://www.theses.fr/2010INPL016N/document.

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L’apparition d’inclusions exogènes demeure un problème majeur pour les élaborateurs de titane. Afin d’améliorer la propreté inclusionnaire des lingots élaborés par le procédé de refusion à l’arc sous vide (Vacuum Arc Remelting), une étude numérique et expérimentale a été réalisée. La partie numérique de la thèse consiste à modéliser le comportement d’un défaut hard-α provenant de l’électrode consommable et tombant dans le puits liquide du lingot. Un modèle décrivant le processus de dissolution prédit l’évolution de la taille d’une inclusion durant son séjour dans le puits liquide. La trajectoire est déterminée à l’aide d’un modèle lagrangien tenant compte de la turbulence de l’écoulement en modifiant le coefficient de trainée. Les deux modèles ont été couplés et implémentés dans le logiciel SOLAR, qui simule la croissance d’un lingot VAR.Les résultats mettent en évidence la difficulté d’éliminer une inclusion hard-α avec une seule refusion, principalement à cause de la croissance d’une couche de phase β pendant les premiers moments de l’immersion. Le comportement global du défaut dépend fortement de l’hydrodynamique du puits et des caractéristiques de l’inclusion.Pour étudier la dissolution expérimentalement, des défautssynthétiques (hard-α et HDI) ont été immergés dans un bain de titane liquide chauffé dans un four à bombardement électronique. Les vitesses de dissolution ont été déterminées en mesurant les dimensions des défauts avant et après les expériences et ont été ensuite utilisées pour valider les modèles numériques. Par ailleurs, nous avons mis en évidence la grande influence de la température et de la vitesse de l’écoulement sur les cinétiques de dissolution
The presence of exogeneous inclusions has always been a major concern for the titanium industry. To help improve the inclusional cleanliness of VAR (Vacuum Arc Remelting) titanium ingots, a numerical and experimental study was undertaken.The numerical model is capable of predicting the motion and dissolution of a hard-α defect falling from the electrode tip into the ingot melt pool during vacuum arc remelting. It is implemented in SOLAR, a CFD code that simulates the ingot growth and solidification. The dissolution of the inclusion is governed by nitrogen diffusion from the defect towards the surrounding molten metal. A model describing this phenomenon predicts the particle size evolution and the nitrogen profile at each moment. The motion of the spherical particle is tracked using a Lagrangian model and the influence of turbulence is accounted for by a modification of the drag coefficient.Results show that inclusion removal is difficult with a single melt since the growth of a β-phase layer leads to an initial increase in the defect size. The inclusion behaviour is highly dependent on the pool hydrodynamics and on inclusion characteristics.In order to clarify dissolution aspects of these defects and to measure their dissolution kinetics, synthetically processed defects were introduced into molten titanium heated in an electron beam melting furnace. Dissolution rates were calculated by measuring the size of the defects before and after the experiments and the results were used to validate the numerical models. Furthermore, the experiments show that dissolution kinetics highly depend on fluid motion and temperature
4

Revil-Baudard, Mathieu. "Modélisation et étude de la macroségrégation au cours de la refusion à l'arc sous vide : application aux alliages de zirconium." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0297/document.

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Le procédé VAR (Vacuum Arc Remelting ou refusion à l'arc sous vide en français) est employé dans la production d'alliages à haute performance pour les industries aéronautique (aciers spéciaux, superalliages et alliages de titane) et nucléaire (alliage de zirconium). Comme pour tous les procédés de fonderie, la maîtrise de l'homogénéité chimique et de la structure métallurgique des lingots coulés par le procédé VAR constitue un enjeu industriel important. Les travaux présentés dans ce mémoire visent à identifier, pour les alliages de zirconium en particulier, les effets de la convection naturelle et de la convection forcée due au brassage électromagnétique sur la macroségrégation. Dans ce but, un modèle numérique a été développé. Il est basé sur la résolution couplée des équations de conservation d'énergie, de quantité de mouvement et de solutés, dans des conditions d'écoulement laminaire ou turbulent. La modélisation de la solidification tient compte du couplage fort entre le transport d'énergie et de solutés dans la zone pâteuse. Afin de décrire la microségrégation, la diffusion restreinte des solutés dans les phases liquides et solides peut être prise en compte. Parallèlement, deux électrodes chimiquement homogènes d'alliages Zircaloy-4 et M5® ont été spécialement refondues dans un four VAR industriel sur le site de CEZUS à Ugine (Savoie, France). La macroségrégation des lingots obtenus a été caractérisée.La comparaison entre les mesures expérimentales et les résultats de simulation a montré que pour un alliage dont l'intervalle de solidification est important (comme l'alliage Zircaloy-4), la convection solutale dans la zone pâteuse peut avoir une influence essentielle sur la macroségrégation de la région centrale du lingot. Par ailleurs, le mouvement de grains équiaxes lors de l'application d'un brassage électromagnétique de forte intensité semble accentuer significativement la macroségrégation dans la région externe du lingot. Pour un alliage dont l'intervalle de solidification est faible (comme l'alliage M5®), nous avons montré que la macroségrégation dépend plus spécifiquement de la convection forcée due au mode de brassage électromagnétique appliqué au cours de la refusion
Vacuum Arc Remelting (VAR) is used to produce high performance alloys for the aeronautic (special steels, superalloys, titanium alloys) and nuclear (zirconium alloys) industries. As for all casting processes, the control of the chemical homogeneity and the metallurgical structure in VAR ingots is an important industrial issue. The goal of this thesis is to identify, for zirconium alloys in particular, the effects of the natural convection and the forced convection due to the electromagnetic stirring on macrosegregation. To this purpose, a numerical model has been developed. It is based on the solution of the coupled transient energy, momentum and solute transport equations, under laminar or turbulent flow conditions. The solidification modeling accounts for a full coupling between energy and solute transport in the mushy zone. The finite diffusion of solutes in both solid and liquid phases can be taken into account to describe microsegregation. In addition, chemically homogeneous Zircaloy-4 and M5® electrodes have been specially remelted in an industrial VAR furnace at the CEZUS plant in Ugine (Savoie, France). The macrosegregation of the ingots has been measured. The comparison between the experimental measurements and the simulation results showed that for an alloy with a large solidification interval (like Zircaloy-4), the solutal convection in the mushy zone could have an essential influence on the macrosegregation in the inner part of the ingot. Furthermore, the motion of equiaxed grains caused by a strong stirring seems to seriously intensify macrosegregation in the outer part of the ingot. For an alloy with a small solidification interval (like M5®), we have shown that the macrosegregation depends more specifically on the forced convection due to the type of stirring applied during the remelting
5

Hans, Stéphane. "Modélisation des transferts couplés de chaleur, de soluté et de quantité de mouvement lors de la refusion à l'arc sous vide (VAR) : application aux alliages de titane." Vandoeuvre-les-Nancy, INPL, 1995. http://www.theses.fr/1995INPL023N.

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L’objectif de ce travail est la modélisation mathématique et numérique du procédé de refusions à l'arc sous vide (VAR), dans le but d'optimiser la refusion d'alliages de titane chargés. En effet, l'intervalle de solidification important de ces alliages les rend sensibles à la formation de défauts de solidification liés à la circulation du liquide interdendritique. Dans le cadre de cette étude, des mesures effectuées par analyse thermique différentielle (ATD) ont permis de quantifier les intervalles de solidification de ces alliages de titane. Le modèle développé décrit les transferts couplés de chaleur, de soluté et de quantité de mouvement en écoulement turbulent, lors de la croissance et de la solidification du lingot VAR. Les transferts au sein de la zone pâteuse sont explicitement pris en compte, celle-ci étant assimilée à un milieu poreux. Le modèle relie directement les paramètres opératoires aux profils de puits liquide, à l'hydrodynamique du bain métallique (convection thermosolutale et forces électromagnétiques) ainsi qu'à l'intensité de la ségrégation dans le lingot. Les simulations effectuées concernent une fusion en four pilote d'un lingotin de titane marqué au cuivre, ainsi que deux fusions industrielles de [Bêta]Cez. Elles ont permis de mettre en évidence l'effet du brassage électromagnétique sur l'écoulement complexe du métal liquide. La prise en compte des transferts au sein de la zone pâteuse permet également de mieux comprendre les phénomènes à l'origine de la macroségrégation. Il apparait que les conditions de brassage des fusions de [Bêta]Cez simulées ont une influence considérable sur l'intensité de la macroségrégation, et donc sur le risque d'apparition de défauts de solidification. Le mécanisme de formation de défauts du type canaux ségrégés, a également été mis en évidence. Dans le cas du [Bêta]Cez, il a été attribué à la convection solutale ascendante de métal liquide fortement appauvri en molybdène. Le modèle peut ainsi être utilisé avec profit afin de choisir les conditions de fusion permettant de minimiser la macroségrégation et donc le risque de formation de défauts
6

Banos, Julien. "Modélisation du procédé de refusion à l’arc sous vide : Échanges thermiques et défauts de solidification." Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0117.

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Le procédé de refusion à l'arc sous vide (Vacuum Arc Remelting ou VAR en anglais) est employé dans la production d'alliages métalliques à haute valeur ajoutée tels que les alliages de titane ou superalliages base nickel à destination de l'industrie aéronautique. La maîtrise des conditions de solidification constitue un enjeu industriel important pour obtenir des lingots d'une homogénéité chimique adéquate et dépourvus de défauts de solidification. Les travaux présentés dans ce document visent à améliorer la description des échanges thermiques dans un modèle du procédé VAR (SOLAR) et proposer une nouvelle approche pour la prédiction des défauts de solidification de type canaux ségrégés. Dans un premier temps, la description dans le modèle des échanges thermiques entre l'électrode, le lingot, la lingotière et le circuit de refroidissement a été améliorée. Les modifications ont fait l'objet de validation par comparaison des résultats numériques avec des mesures sur des refusions industrielles réelles. Un dispositif expérimental original de mesure de température à la paroi extérieure de la lingotière adapté aux refusions industrielles a été conçu et utilisé lors d'une campagne expérimentale sur site industriel lors de la refusion d'un alliage de titane. Les mesures obtenues ont été confrontées aux résultats numériques de SOLAR. Ces deux activités ont abouti à une première implémentation du phénomène de side-arcing dans le modèle. En parallèle, une approche numérique multi-échelle a été développée pour prédire la formation de canaux ségrégés en fonction des conditions locales de solidification. Une première étude sur un alliage Sn-Pb a été réalisée et un critère mathématique de prédiction a été calculé à partir des résultats. Cette première étude montre un impact du gradient thermique sur la formation de canaux ségrégés bien plus faible que celui généralement considéré dans la littérature
The Vacuum Arc Remelting (VAR) process is used in the production of high-added value metals such as titanium alloys or nickel-based superalloys for the aerospace industry. The control of solidification conditions is an important industrial issue in order to process ingots of adequate chemical homogeneity and free of solidification defects. The work presented in this manuscript aims at improving the description of heat exchanges in a VAR process model (SOLAR) and at proposing a new approach for the prediction of segregated channels type solidification defects. First, the description of the heat exchanges in the model between the electrode, the ingot, the mould and the cooling circuit has been improved. These modifications were validated by comparing the numerical results with measurements from real industrial melts. An original experimental apparatus for measuring the external mould temperature adapted to industrial melts was designed. This apparatus was used during an experimental campaign on an industrial site during the remelting of a titanium alloy. The measurements obtained were compared with the numerical results from SOLAR. These two activities led to a first implementation of the side-arcing phenomenon in the model. In parallel, a multi-scale numerical approach was developed to predict the formation of segregated channels as a function of local solidification conditions. A first study on a Sn-Pb alloy was carried out and a mathematical criterion was calculated from the results. This first study shows a much lower impact of the thermal gradient on the formation of segregated channels than that generally considered in the literature
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Wani, Nitin Yashwant. "Simulation of thermal stresses in vacuum arc remelting process." Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1178820121.

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Hosamani, Laxmappa G. "Experimental and theoretical heat transfer studies in vacuum arc remelting /." Full text open access at:, 1988. http://content.ohsu.edu/u?/etd,166.

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Xu, Xuahua. "Grain development during vacuum arc remelting of nickel based superalloys." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368958.

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MUCSI, CRISTIANO S. "Estudo sobre o processo V.A.R. (Vacuum Arc Remelting) escala de laboratorio." reponame:Repositório Institucional do IPEN, 1996. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10472.

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Book chapters on the topic "Vacuum Arc Remelting (VAR)":

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Sartkulvanich, Partchapol, Don Li, Oscar Yu, Ernie Crist, and Shane Probst. "Applications of Finite Element Modeling on Vacuum ARC Remelting (VAR) and Plasma ARC Melting (PAM) Processes of Titanium Alloys." In Proceedings of the 13th World Conference on Titanium, 365–69. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119296126.ch56.

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Xianghua, Shao, Li Shiqi, and Xu Kuangdi. "Vacuum Arc Remelting." In The ECPH Encyclopedia of Mining and Metallurgy, 1–2. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-0740-1_999-1.

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Zhang, W., P. D. Lee, and M. McLean. "Inclusion Behaviour During Vacuum Arc Remelting of Nickel Based Superalloys." In Intermetallics and Superalloys, 121–28. Weinheim, FRG: Wiley-VCH Verlag GmbH & Co. KGaA, 2006. http://dx.doi.org/10.1002/3527607285.ch21.

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Pericleous, Koulis, Georgi Djambazov, Mark Ward, Lang Yuan, and Peter D. Lee. "A Multi-Scale 3D Model of the Vacuum Arc Remelting Process." In Supplemental Proceedings, 291–98. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118357002.ch38.

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McCulley, Daniel, Joshua Motley, Matthew Cibula, and Paul King. "Elucidating the Relationship Between Arc Behavior and Solidification Defects During Vacuum Arc Remelting of Superalloys." In The Minerals, Metals & Materials Series, 994–1003. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-92381-5_95.

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King, Paul E., Matthew Cibula, and Joshua Motley. "Control of the Distribution of Vacuum Arcs Within Vacuum Arc Remelting with Externally Applied Magnetic Fields." In 11th International Symposium on High-Temperature Metallurgical Processing, 273–87. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-36540-0_25.

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Patel, Ashish, David W. Tripp, and Daniel Fiore. "Application of a Model for Simulating the Vacuum Arc Remelting Process in Titanium Alloys." In Proceedings of the 2013 International Symposium on Liquid Metal Processing and Casting, 239–44. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2013. http://dx.doi.org/10.1002/9781118830857.ch35.

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Patel, Ashish, David W. Tripp, and Daniel Fiore. "Application of a Model for Simulating the Vacuum Arc Remelting Process in Titanium Alloys." In Proceedings of the 2013 International Symposium on Liquid Metal Processing & Casting, 241–44. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-319-48102-9_35.

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Cibula, M., J. Motley, N. Pettinger, D. McCulley, and P. King. "Advances in Magnetic Measurements and Externally Applied Magnetic Fields for Vacuum Arc Remelting Process Monitoring and Control." In The Minerals, Metals & Materials Series, 1609–22. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-50349-8_139.

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"Computational Analysis of the Vacuum Arc Remelting (VAR) and Electroslag Remelting (ESR) Processes." In Metals Process Simulation, 196–213. ASM International, 2010. http://dx.doi.org/10.31399/asm.hb.v22b.a0005510.

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Conference papers on the topic "Vacuum Arc Remelting (VAR)":

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Alam, M. K., K. K. Wong, and S. L. Semiatin. "Elasto-Plastic Analysis of Thermal Stress Development During VAR of Ingots." In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0631.

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Abstract The vacuum arc remelting (VAR) process has been developed to melt and cast high quality aerospace materials such as titanium alloys. VAR comprises the continuous remelting of a consumable electrode by means of a dc arc under vacuum or a low partial pressure of argon. The molten metal solidifies in a water-cooled copper crucible leading to high cooling rates that often results in large thermal stresses. The development of temperature gradients and the resulting thermal stresses during the VAR processes was investigated using an elasto-plastic material model with temperature dependent thermomechanical properties. Detailed solutions were obtained by using the commercial finite element code ABAQUS.
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Lopez, Luis Felipe, Joseph J. Beaman, and Rodney L. Williamson. "A Reduced-Order Model for Dynamic Vacuum Arc Remelting Pool Depth Estimation and Control." In ASME 2011 Dynamic Systems and Control Conference and Bath/ASME Symposium on Fluid Power and Motion Control. ASMEDC, 2011. http://dx.doi.org/10.1115/dscc2011-5958.

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Vacuum arc remelting (VAR) is an industrial metallurgical process widely used throughout the specialty metals industry to cast large alloy ingots. A reduced-order model of the growing and solidifying ingot was developed specifically for dynamic control and estimation of the depth of molten liquid pool atop the ingot in a VAR process. This model accounts only for the thermal aspects of the system ignoring high-fidelity physics such as fluid flow and electromagnetic effects. Spectral methods were used to obtain a set of nonlinear dynamic equations which capture the transient characteristics of liquid pool shape variations around a quasi-steady operating condition. These nonlinear equations are then linearized about this operating condition and further simplified by suppressing fast modes. The resulting system can be described by only six state variables. The reduced order model compares favorably to pool depth changes predicted by an accurate finite-volume model. A first approach to use this model in the design of a dynamic VAR pool depth estimator and controller is also proposed.
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Beaman, Joseph J., Rodney L. Williamson, David K. Melgaard, and Jon Hamel. "A Nonlinear Reduced Order Model for Estimation and Control of Vacuum Arc Remelting of Metal Alloys." In ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-79239.

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Vacuum arc remelting (VAR) is an industrial metallurgical process widely used throughout the specialty metals industry to cast large alloy ingots. The VAR process is carried out in a vacuum with the aim of melting a large consumable electrode (.4 m in diameter and 3000 kg in mass and larger) in such a way that that the resulting ingot has improved homogeneity. The VAR control problem consists of adjusting arc current to control electrode melt rate, which also depends on the electrode temperature distribution and adjusting electrode ram speed to control the arc gap between the electrode and the ingot. The process is governed by a 1 dimensional heat conduction partial differential equation with a moving boundary, which leads to an infinite dimensional, nonlinear system. In addition to the process nonlinearity, the inputs and all of the available measurements are corrupted with noise. In order to design a controller and a Kalman based estimator for this process, integral methods are used to derive a set of two coupled nonlinear ordinary differential equations in time, which capture the steady state and transient characteristics of melting in a VAR furnace. The model with the experimentally measured noise is then used to construct an estimator and a controller. The system can be described by two state variables that change in time: thermal boundary layer and melted length or alternatively electrode gap. The reduced order model compares favorably to an accurate finite difference model as well as melting data acquired for Ti-6Al-4V. It will be shown how this model can be used to obtain dynamic closed loop melt rate control while simultaneously controlling electrode gap. This controller and estimator were tested on a laboratory furnace at Timet.
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Zanner, F. J., R. L. Williamson, R. P. Harrison, H. D. Flanders, R. D. Thompson, and W. C. Szeto. "Vacuum ARC Remelting of Alloy 718." In Superalloys. TMS, 1989. http://dx.doi.org/10.7449/1989/superalloys_1989_17_32.

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Grose, S. M. "The Vacuum Arc Remelting of Large Diameter Alloy 706." In Superalloys. TMS, 1994. http://dx.doi.org/10.7449/1994/superalloys_1994_49_53.

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Williamson, R. L., and G. J. Shelmidine. "Current Paths During Vacuum Arc Remelting of Alloy 718." In Superalloys. TMS, 2001. http://dx.doi.org/10.7449/2001/superalloys_2001_91_102.

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Patel, A. D., R. S. Minisandram, and D. G. Evans. "Modeling of Vacuum Arc Remelting of Alloy 718 Ingots." In Superalloys. TMS, 2004. http://dx.doi.org/10.7449/2004/superalloys_2004_917_924.

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Williamson, R. L., M. E. Schlienger, C. L. Hysinger, and J. J. Beaman. "Modern Control Strategies for Vacuum Arc Remelting of Segregation Sensitive Alloys." In Superalloys. TMS, 1997. http://dx.doi.org/10.7449/1997/superalloys_1997_37_46.

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Liu Xin, Zhang Nailu, Guo Chaoyang, and He Li. "Research on arc stability control system for vacuum arc remelting furnace based on fuzzy-PID." In 2014 IEEE Workshop on Electronics, Computer and Applications (IWECA). IEEE, 2014. http://dx.doi.org/10.1109/iweca.2014.6845547.

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Williamson, R. L., J. J. Beaman, F. J. Zanner, and J. J. DeBarbadillo. "Advancing Alloy 718 Vacuum Arc Remelting Technology Through Developing Model-Based Controls." In Superalloys. TMS, 2005. http://dx.doi.org/10.7449/2005/superalloys_2005_47_56.

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