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Temperature character of electromagnetic levitation melting

Ma Wei-Zeng,Ji Cheng-Chang,Li Jian-Guo,Xu Zhen-Ming,

物理学报 , 2003,
Abstract: Utilizing the formula of electromagnetic force and input power, we have derived the expression of input power of a spherical sample for a general electromagnetic levitation inductor without including the current of the inducer. Combining the power dissipation model of the spherical sample in free-convection gas medium and the expression of input power without including the current of inducer, the relation between processing parameters of electromagnetic levitation and temperature of levitation sample is established. The electromagnetic melting of spherical (TbDy)Fe2 alloys under the protection of Ar is employed as an example to study the effect of processing parameters on the temperature of levitation sample obtained by numerical computation. According to computation results and the character of actual electromagnetic levitation, the methods to decrease the temperature of the levitation melted sample are obtained: i.e. reducing the radius of the levitation melted sample, employing low frequencies of the inducer, adjusting the position of the levitated sample to a position at which the lowest levitation melting temperature can be obtained, reducing the radius of the lower levitation coil, increasing the space interval between the upper stability controlling coil and the lower levitation coil, increasing the radius of the upper stability controlling coil, and increasing the turns of the upper stability controlling coil.

金属学报 , 1996,
Abstract: The electrochemical activation behaviours of the hydrogenstorage electrode alloys Ml(Ni,Co,Mn,Ti)5 produced by induction melting and then fornace cooling (FC) or Ar-gas atomizing (AGA) have been studied by comparing the activation of AGA electrodes aged at room temperature for 4 months with that of FC electrode. It is found that the surface oxide is only a minor factor to affect the activation, while the magnitude of internal energy change in the alloy before and after hydrogenation is the controlling factor. The increases in the internal energy of the alloy, caused by oxide and the H-atoms entering tetrahedral or octahedral sites during hydrogenation, make the activation difficult.
Solubility of nitrogen in liquid Fe-10Ti and Fe-25Ti alloys  [PDF]
A. Hutny,J. Siwka
Journal of Achievements in Materials and Manufacturing Engineering , 2012,
Abstract: Purpose: of the study was to determine the physicochemical characteristics of thermodynamic equilibrium in the liquid metal-gas system, where the liquid metal was a liquid Fe-Ti alloy, and the reaction gas was always a mixture of nitrogen and argon with preset chemical composition.Design/methodology/approach: In the experimental studies, the levitation metal melting technique was used, which enabled, on the one hand, the liquid metal-gas thermodynamic system appropriate to the purpose to be fabricated and, on the other hand, precise measurements to be carried out within a wide nitrogen partial pressure range from 0.0005 to 0.070 atm and in the appropriate range of metal temperature variations (1973-2273 K). The solidification of a 1 g-mass sample at a rate higher than 1000 K/s assured the complete nitrogen fixation in the solidified sample compared to the liquid-state sample.Findings: It has been established in the study by experimentally measuring the nitrogen concentration in the liquid Fe-Ti alloy with varying titanium contents under hyperbaric conditions that the solubility of nitrogen in liquid Fe-Ti alloys increases with increasing partial pressure of nitrogen in the gaseous phase, and with increasing liquid metal temperature and titanium content of the metal.Research limitations/implications: The study has found that when the intensive parameters increase above the critical values, the non-metallic phase forming on the levitating metal drop surface is a titanium nitride film, as demonstrated by X-ray analysis. Such samples were eliminated from the characteristics of nitrogen solubility in the homogeneous metallic phase.Practical implications: The collected data on the thermodynamic quantities of the liquid Fe-Ti-N alloy has enriched the autonomous thermodynamic database containing information about liquid alloys of iron with nitrogen, which is being built at Czestochowa University of Technology.Originality/value: The developed formulas seem to be valuable, because - as the relevant literature indicates - the Fe-Ti system has not been examined so far under such extreme thermodynamic conditions.
K Deng,ZM Ren,JQ Chen,GC Jiang School of Materials,Shanghai University,Shanghai,China,
K. Deng
,Z.M. Ren,J.Q. Chen and G.C. Jiang School of Materials,Shanghai University,Shanghai,China

金属学报(英文版) , 2000,
Abstract: In this paper, using the quasi-3D coupled current method, the influences of structure of cold crucible, the power frequency, the electricity property of melt, the coil position and current on the electromagnetic field (EMF) and the levitation characteristics in the melting processes are analyzed. It is shown that in the processes of levitation melting with cold crucible, the power frequency and cold crucible structure are the decisive factors for the ability of magnetic flux penetrating into cold crucible. The magnetic flux density in cold crucible is reduced as the increasing of power frequency, and this tendency becomes stronger when the power frequency is higher than 100kHz. The segmented structure of cold crucible can reduce the induction eddy in itself effectively, and the higher the power frequency is, the better the result is. So, a cold crucible can be segmented into 16-20 sectors for high frequency electromagnetic field and/or 8-12 sectors for lower frequency one. It is also shown that the levitation force of melting charge is related to coil current as a parabolic function.
Microstructures and Properties for a Superalloy Powder Mixture Processed by Electron Beam Melting  [cached]
J. Hernandez,L. E. Murr,K. N. Amato,E. Martinez
Journal of Materials Science Research , 2012, DOI: 10.5539/jmsr.v1n3p124
Abstract: The microstructures and residual hardnesses for solid components of 2-phase TiAl (Ti-48Al-2Nb-2Cr in a/o) and Inconel 625 (Ni-19Cr-9Mo-4Nb in w/o) fabricated by electron beam melting (EBM) were compared with a 10:1 blend of TiAl: alloy 625 pre-alloyed powders producing a complex alloy having the composition 48Ti-24Al-9Ni-8Nb-4.5Cr-4Ni (in w/o). The blended alloy hardness (HV) reached 7.5 GPa in contrast to 1.4 GPa for the Alloy 625 and 4.0 for the 2-phase TiAl alloy. Reticulated mesh samples and stochastic foam samples prepared from the blended alloy by EBM exhibited a relative stiffness versus relative density plotted on a log-log basis consistent with other reference alloys fitted to a straight line with a slope n = 2 for ideal open cellular materials.
Influence of melt hydrogenation during induction skull melting process on the solidification microstructure of Ti-6Al-4V alloy  [PDF]
Zhang Yuehong,Su Yanqing,Ye Xicong
China Foundry , 2010,
Abstract: A new method to modify the solidification microstructure of titanium alloys, named melt hydrogenation, by adding TiH2 as additive into the melt of titanium alloys during induction skull melting process (ISM), is put forward and the refining effect of this method on the solidification microstructure of Ti-6Al-4V alloy was studied experimentally. After melt hydrogenation, the grain sizes of as-cast Ti-6Al-4V alloy decreased to 612 μm from 1,072 μm, lath-shaped α phase was also refined and fine α/β lamellar microstructure was formed when 1.0 wt.% TiH2 was added. δ-hydride was found in the X-ray diffraction (XRD) spectra of Ti-6Al-4V alloy that prepared with 1.0 wt.% TiH2 added and the δ-hydride distributes in α phase as acicular precipitations.
Determination of critical current density in melt-processed HTS bulks from levitation force measurements  [PDF]
A. A. Kordyuk,V. V. Nemoshkalenko,R. V. Viznichenko,T. Habisreuther,W. Gawalek
Physics , 1999, DOI: 10.1063/1.124765
Abstract: A simple approach to describe the levitation force measurements on melt-processed HTS bulks was developed. A couple of methods to determine the critical current density $J_c$ were introduced. The averaged $ab$-plane $J_c$ values for the field parallel to this plane were determined. The first and second levitation force hysteresis loops calculated with these $J_c$ values coincide remarkably well with the experimental data.
Development of the fundamentals of melting and casting technology of Al-Me (Cr, Ni, Mo, W, Ti) master alloys used for modification of microstructure in silumins  [PDF]
J. Piatkowski
Archives of Foundry Engineering , 2009,
Abstract: The study presents the technological backgrounds of the process of melting and casting Al-Cr, Al-Ni, Al-Mo, Al-W and Al-Ti masteralloys, used as refiners of the microstructure of cast silumins. Basing on the analysis of phase equilibrium diagrams for an Al-Me (Cr, Ni, Mo, W, Ti) system at a temperature of 900oC, the characteristic intermetallic phases of AlxMey were investigated. Due to their similarity with Al and Si in respect of both structure and lattice arrangement, these phases may act as heterogeneous nuclei and promote solution hardening during, e.g., heat treatment. Using the method of thermal analysis ATD, the temperature was plotted in function of time, and then the characteristic values of the solidification parameters of master alloys were read out from the respective curves.
Ingredient Losses during Melting Binary Ni-Ti Shape Memory Alloys
SKSadrnezhaad,SBadakhshan Raz,
,S.Badakhshan Raz

材料科学技术学报 , 2005,
Abstract: Losses of the alloying elements during vacuum induction melting of the binary NiTi alloys were evaluated by visual observation and chemical analysis of the NiTi melted specimens and the scalp formed on the internal surface of the crucible. The results indicated that the major sources of the losses were (a) evaporation of the metals, (b) formation of the NiTi scalp and (c) the sprinkling drops splashed out of the melt due to the exothermic reactions occurring between Ni and Ti to form the NiTi parent phase. Quantitative evaluations were made for the metallic losses by holding the molten alloy for 0.5, 3, 5, 10 and 15 min at around 100℃ above the melting point inside the crucible.Chemical analysis showed that there existed an optimum holding time of 3 min during which the alloying elements were only dropped to a predictable limit. Microstructure, chemical composition, shape memory and mechanical properties of the cast metal ingots were determined to indicate the appropriate achievements with the specified 3 min optimum holding time.
Corrosion Behavior of Fe40Al Alloy with Additions of Ti, Ag, and Cr in Molten KCl+  [PDF]
R. Ademar,J. G. Gonzalez-Rodriguez,J. Uruchurtu,J. Porcayo-Calderon,V. M. Salinas-Bravo,G. Dominguez-Pati?o,A. Bedolla-Jacuinde
International Journal of Corrosion , 2012, DOI: 10.1155/2012/146486
Abstract: The effect of 2.5?at.% Cr, Ti, and Ag on the corrosion behavior of Fe40Al intermetallic alloy in KCl-ZnCl2 (1?:?1?M) at 670°C has been evaluated by using electrochemical techniques. Techniques included potentiodynamic polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) measurements. Results have shown that additions of both Cr and Ti were beneficial to the alloy, since they decreased its corrosion rate, whereas additions of Ag was detrimental, since its additions increased the corrosion rate, although the alloy was passivated by adding Ag or Cr. The best corrosion performance was obtained with the addition of Cr, whereas the highest corrosion rate was obtained by adding Ag. This is explained in terms of the stability of the corrosion products formed film. 1. Introduction Sodium and potassium impurities present in the form of chloride or sulfates are very corrosive constituents under certain combustion conditions such as waste incinerators and biomass-fired boilers [1, 2]. Early failure of the thermal components frequently occurs due to the complex reactions between the metallic materials and the hostile combustion environment. Incineration has become a viable technology for disposing of various types of wastes, including municipal, hospital, chemical, and hazardous. Problems with process equipment resulting from fireside corrosion have been frequently encountered in incinerators. The major problem is the complex nature of the feed (waste) as well as corrosive impurities which form low-melting point compounds with heavy and alkali metal chloride which prevents the formation of protective oxide scales and then causes an accelerated degradation of metallic elements [1]. In particular, under reducing conditions such as those typical of the operation of waste gasification plants or even under localized reducing conditions, which frequently arise in the case of incorrect operation of waste incineration systems, it is difficult to form protective oxide scales such as Cr2O3, SiO2, and Al2O3 on the surface of structural materials. Thus, the corrosion attack can be further enhanced under reducing atmospheres in the presence of salt deposits [2]. The effect of individual KCl, NaCl, and their mixtures with heavy metal chlorides or sulfates on the corrosion behavior of a series of alloy systems has been studied in detail so far [3–9]. It is generally realized that Cr is not as effective element for corrosion resistance of Fe-base and Ni-based alloys due to chloride attack. In contrast, alumina- (Al2O3) forming
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