High-frequency Induction Furnace Research Articles

Salt-flux growth of HoCuMg4 single crystals.

Polycrystalline samples of the magnesium-rich intermetallic compounds RECuMg4 (RE = Dy, Ho, Er, Tm) were synthesized by reaction of the elements in sealed tantalum ampoules heated in a high-frequency induction furnace. Phase purity of the RECuMg4 phases was ascertained by powder X-ray diffraction patterns. Well-shaped single crystals of HoCuMg4 could be grown in a NaCl/KCl salt flux and the crystal structure was refined from single crystal X-ray diffraction data: TbCuMg4 structure-type, space group Cmmm, a = 1361.4(2), b = 2039.3(4), c = 384.62(6) pm. The crystal structure of the RECuMg4 phases can be understood as a complex intergrowth variant of CsCl and AlB2 related slabs. The remarkable crystal chemical motif concerns the orthorhombically distorted bcc-like magnesium cubes with Mg-Mg distances ranging from 306 to 334 pm. At high temperatures DyCuMg4 and ErCuMg4 are Curie-Weiss paramagnets with paramagnetic Curie-Weiss temperatures of -15 K and -2 K for RE = Dy and Er, respectively. The effective magnetic moments, 10.66μB for RE = Dy and 9.65μB for RE = Er prove stable trivalent ground states for the rare earth cations. Magnetic susceptibility and heat capacity measurements reveal long-range antiferromagnetic ordering at low temperatures (<21 K). Whereas DyCuMg4 exhibits two subsequent antiferromagnetic transitions at TN = 21 and 7.9 K which successively remove half of the entropy of a doublet crystal field ground state of Dy, ErCuMg4 shows a single, possibly broadened, antiferromagnetic transition at 8.6 K. The successive antiferromagnetic transitions are discussed with respect to magnetic frustration in the tetrameric units present in the crystal structure.

Study the ability of using basic oxygen furnace slag as a flux for removing impurities from liquid iron in a pre-treatment process

In this study, a flux, mixture of basic oxygen furnace (BOF) slag and CaO powder, was investigated the ability of the slag recycling in a pre-treatment process. The first step of the experimental procedure was to melt iron using a high-frequency induction furnace, then 3 kg of flux was embedded into the metal. There were two kinds of experimental conditions including with and without Argon gas protection of the furnace. After ten minutes from the moment of adding the flux, the metal and slag samples were taken out for chemical composition analysis. The results showed that Sulphur (S) content of the iron significantly decreased by 38% and 19% with and without the Argon gas protection, respectively. Meanwhile, the Phosphorus (P) content of the iron was concluded to be independent of the conditional experiments. Besides, the Fe content of the slag decreased in both cases of experiments.

Electrochemical Behavior of Inductively Sintered Al/TiO2 Nanocomposites Reinforced by Electrospun Ceramic Nanofibers.

This study is focuses on the investigation of the effect of using TiO2 short nanofibers as a reinforcement of an Al matrix on the corrosion characteristics of the produced nanocomposites. The TiO2 ceramic nanofibers used were synthesized via electrospinning by sol-gel process, then calcinated at a high temperature to evaporate the residual polymers. The fabricated nanocomposites contain 0, 1, 3 and 5 wt.% of synthesized ceramic nanofibers (TiO2). Powder mixtures were mixed for 1 h via high-energy ball milling in a vacuum atmosphere before being inductively sintered through a high-frequency induction furnace at 560 °C for 6 min. The microstructure of the fabricated samples was studied by optical microscope and field emission scanning electron microscope (FESEM) before and after corrosion studies. Corrosion behavior of the sintered samples was evaluated by both electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques (PPT) in 3.5% NaCl solution for one hour and 24-h immersion times. The results show that even though the percentage of ceramic nanofibers added negatively control corrosion resistance, it is still possible to increase resistance against corrosion for the fabricated nanocomposite by more than 75% in the longer exposure time periods.

Effect of White Mud Addition on Desulfurization Rate of Molten Steel

Fluorspar (CaF2) is commonly used to control the fluidity of slag in ladle-refining of steel. However, because it is desirable to reduce CaF2 consumption because of its environmental impacts, the industrial waste material such as white mud (WM) was investigated as a potential substitute for fluorspar. Steel sample (Fe-0.3C-0.9Mn-0.3Si-0.03Al-0.05S, mass pct) was melted in a high-frequency induction furnace, followed by additions of ladle slag (CaO-Al2O3-SiO2-5MgO-xCaF2, CaO/Al2O3=3, x = 0 to 10 mass pct) and fluxing agent (WM) at 1823 K (1550 °C). The desulfurization experiments were carried out by reducing CaF2 content in the ladle slag and increasing the addition of WM. Ladle slag with added WM showed an overall mass transfer coefficient of sulfur (kO) equivalent to or higher than that of conventional 10 mass pct CaF2-containing ladle slag. In a slag melting experiment based on DIN 51730 standard, the melting rate of mixed slag increased with the amount of WM added, which is considered to have a positive effect on the initial desulfurization rate. In addition, adding WM provided sulfide capacity of the slag equivalent to that of CaF2-containing slag. Consequently, the use of WM yielded slag having k_{{text{O}}} equivalent to or higher than that of conventional ladle slag with 10 pct CaF2, and thus, WM shows promise as a partial replacement for fluorspar.

Comparative study between the melting process of an aluminum batch and a steel batch in a high frequency induction furnace

In this work we analyzed a laboratory induction furnace, having a small capacity, fed by a high-frequency static converter. The measurements were carried out in the case of an aluminum batch, and a steel batch, using the power quality analyzer CA8334B. We studied the influence of the type, temperature and amount of processed material, on the electrical parameters of induction furnace during the melting process. Large electromagnetic disturbances (harmonic currents, current unbalances, reactive power consumption) were recorded, especially during the preheating period of crucible and the first stage of heating, when the furnace worked at low power, for the both batches. The experiments allowed the elaboration of some measures for optimization of melting process in the analyzed induction furnace, in terms of efficiency and mitigation of electromagnetic disturbances.

Study of the silica–magnesia relationship in silicate slags on electrical conductivity at high temperature

Slags are metallurgical aggregates with beneficial minerals and in some processes, they constitute the most abundant mass of the operation and for this reason their control is necessary. These materials have physicochemical behaviors that serve to model the process variables. A particular condition of silicate slags in processes for obtaining some ferroalloys is that there are relationships between compounds that allow predicting the behavior of other variables, these relationships are maintained during production. This study aims to know the electrical behavior of a slag so that the data will contribute to have an additional control in the operation of an electric arc furnace. An alumina content of up to 50% was gradually added to one sample and the other was remelted on three occasions, for all cases the electrical conductivity was determined at a temperature between 1400 °C and 1600 °C. For the electrical resistance value, a Miller 400 type resistivity measurement advice was used, and the temperature was achieved by melting the samples in a high-frequency induction furnace with a collapsible silicon carbide crucible, lined with high-grade refractory alumina. Analysis of the electrical conductivity data for silicate slags made it possible to demonstrate that they are proportional to the values of the major oxides of the slag in their silica-magnesia ratio.

Study on the Possible Error Due to Matrix Interaction in Automated SEM/EDS Analysis of Nonmetallic Inclusions in Steel by Thermodynamics, Kinetics and Electrolytic Extraction

Up to now, the Fe content of nonmetallic particles has often been neglected in chemical evaluations due to the challenging analysis of matrix elements in nonmetallic inclusions (NMI) in steel by scanning electron microscope and energy dispersive spectroscopy analysis (SEM/EDS). Neglecting matrix elements as possible bonding partners of forming particles may lead to inaccurate results. In the present study, a referencing method for the iron content in nonmetallic inclusions in the submicrometer region is described focusing on the system Fe-Mn-O. Thermodynamic and kinetic calculations are applied to predict the inclusion population for different Fe/Mn ratios. Reference samples containing (Fe,Mn)-oxide inclusions with varying Fe ratios are produced by manganese deoxidation in a high-frequency induction furnace. Subsequent SEM/EDS measurements are performed on metallographic specimens and electrolytically extracted nonmetallic inclusions down to 0.3 µm. The limits of iron detection in these particles, especially for those in the submicrometric regime, as well as the possible influence of electrolytic extraction on Fe-containing oxide particles are examined. The measured inclusion compositions correlate well with the calculated results regarding segregation and kinetics. The examinations performed are reliable proof for the application of SEM/EDS measurements to evaluate the Fe content in nonmetallic inclusions, within the physical limits of polished cross-section samples. Only electrolytic extraction ensures the determination of accurate compositions of dissolved or bonded matrix elements at smallest particles enabling quantitative particle descriptions for submicrometric (particles ≤ 1 µm) steel cleanness evaluations.

Release behavior of radionuclides from MOX fuels irradiated in a fast reactor during heating tests

In order to obtain the release rate coefficients from fuels for fast reactors (FRs), heating tests and the subsequent analyses of the fission products (FPs) and actinides that are released were carried out using samples of uranium-plutonium mixed oxide (MOX) fuel pellets irradiated at the experimental fast reactor Joyo. Three heating tests targeting temperatures of 2773, 2973 and 3173 K were conducted using an FP release behavior test apparatus equipped with a high-frequency induction furnace and solid FP sampling systems consisting of a thermal gradient tube (TGT) and filters. Irradiated fuel pellets were placed into a tungsten crucible, then loaded into the induction furnace. The temperature was raised continuously at a heating rate of 10 K/s to the targeted temperature and maintained for 500 s in a flowing argon gas atmosphere. The FPs and actinides released from the MOX fuels and deposited in the TGT and filters were quantified by gamma-ray spectrometry and inductively coupled plasma mass spectrometry analysis. Based on the analysis, the release rates of radionuclides from MOX fuels for FRs were obtained and compared with literature data for light water reactor (LWR) fuels. The release rate coefficients of FPs obtained in this study were found to be similar to or lower than the literature values for LWR fuels. It was also found that the release rate coefficient data for actinides were within the range of variation of literature values for LWR fuels.

Corrosion Resistance of Zn-Al-Mg Alloys with Hypoeutectic Microstructure

Zn-Al-Mg alloys with hypoeutectic microstructure were melted through a high frequency induction furnace. The content of aluminum and magnesium in the alloys were between 1% to 2%. Scanning electron microscopy (SEM) was utilized to analyze microstructure and phase, respectively. Effect of alloying element contents on corrosion resistance was studied. Results show that the Zn-Al-Mg alloys are almost covered by primarily solidified Zn rich block phase and fine lamellar binary and ternary eutectic microstructure exist between the Zn rich phase. The corrosion resistance was characterized through electrochemical test which indicates that increasing Al and Mg content in the Zn-Al-Mg alloys decline corrosion current density. For alloys with 1% Al, more magnesium means lower corrosion potential. For alloys with 2% Al, however, more magnesium suggests higher corrosion potential. In Nyquist curves of electrochemical impedance spectroscopy (EIS) test, Warburg impedance portion could be found for all alloys. With increasing alloying elements content in the Zn-Al-Mg alloys, charge transfer resistance in higher frequency remarkably increase, which implies higher corrosion resistance.

Development of high strength austempered ductile iron (ADI) from conventional pig iron

An alloy ductile iron can be transformed into high strength austempered ductile iron (ADI) by transforming ferritic-pearlitic matrix into ausferrite after subjecting to austempering heat-treatment process. ADI can be used for making complex shapes components for high strength applications owing to its castability. The present work aims to develop ductile iron containing Ni and Mo using low cost conventional pig iron rather than expensive Sorel pig iron by ladle sandwich method in a commercial high-frequency induction furnace. Effect of austempering time ranging from 30 to 120 min at austempering temperatures of 265 °C and 330 °C on microstructure and mechanical properties of resulting ADI was evaluated. Results showed that ADI developed from the cost-effective ductile iron produced by pig iron have mechanical properties comparable to ADI developed using Sorel pig. Optical and scanning electron microscopy revealed that large size graphite nodules were formed in the matrix of ausferrite and retained austenite at 265 °C austempering for 30 min. Increasing austempering time resulted in an increase in ausferrite fraction with the decrease in retained austenite fraction. ADI developed by austempering at 330 °C resulted in a small fraction of ausferrite and a large fraction of retained austenite compared to that developed at 265 °C. Austempering heat treatment process considerably improved mechanical properties of ductile iron at both tempering temperatures (265 and 330 °C). The tensile strength, elongation and hardness of ADI produced by austempering at 265 °C for 90 min soaking time increased by 42, 83 and 26% compared to that produced at 330 °C for 90 min.

Effect of interactions between Fe–Al alloy and MgO-based refractory on the generation of MgO·Al2O3 spinel

ABSTRACTIn the present study, interactions between Fe-2.1 wt-%Al and Fe-5.1 wt-%Al alloys and different tundish refractories, and a spinel generation in the Fe–Al alloys were investigated in laboratory experiments at 1550°C in an alumina crucible using a high-frequency induction furnace. The results indicated that the formation of a spinel layer at the interface was owing to both the oxidation–reduction reactions and the phase transformation at the interface according to initial phases in refractories. The thickness of the interface layer increased with increasing the content of the [Al] in Fe–Al alloys, the SiO2 content in the refractory and the immersion time, however, the [Al] content was a dominant factor. Both experimental results and thermodynamic calculations concluded that MgO·Al2O3 spinel inclusions along with a small amount of CaO–MgO–Al2O3 were the main inclusions in Fe–Al alloys. MgO·Al2O3 inclusions were mainly formed at the interface by alloy/refractory interactions and then mechanically transferred into molten alloys.

Mechanism of Interface Reactions Between Fe-2%Al Alloy and High-Silica Tundish Refractory

The reactions between a Fe-2%Al alloy and a high-silica tundish refractory were investigated at 1550 °C in an alumina crucible using a high-frequency induction furnace. The reaction between the dissolved aluminum in the molten alloy and the oxidizing components in the refractory took place at the interface, generating a MgO·Al2O3 spinel as the main product, which was confirmed by both experimental and FactSage™ 7.0 calculated results. Several layers were detected at the interface depending on an aluminum diffusion in the refractory material and the reaction time. However, the formation of MgO·Al2O3 spinel layer at the interface delayed the reduction of silica because aluminum diffusion became very slow through the interfacial layer. The mass transfer coefficient of silicon in the Fe-2%Al alloy was 7.91 × 10−4 m/s. FactSage™ 7.0 calculated results indicated that the content of silicon in the alloy was higher than that of magnesium, as the result of transformation of forsterite phase to MgO·Al2O3 spinel at the interface.

Separation mechanism of TiSi2 crystals from a Ti-Si eutectic alloy via directional solidification

TiSi2 crystals were successfully obtained via directional solidification separation of a Ti–Si eutectic alloy under electromagnetic stirring. In order to explore the separation mechanism in detail, experiments were conducted using a high-frequency induction furnace at different downward speeds and by varying the thermal parameters of directional solidification (i.e., temperature gradient, cooling rate, and growth rate) of a crucible loaded with Ti–75 wt%Si melt. The results demonstrate that electromagnetic stirring and the thermal parameters of directional solidification played different roles in the crystal separation of TiSi2. While the electromagnetic stirring enhanced the migration of TiSi2 crystals in the Ti–Si melt and mushy zone, low downward rates (5 μm/s) were beneficial for the growth of TiSi2 crystals and reduced the mushy zone area. Therefore, a low downward rate combined with electromagnetic stirring is favorable for the enrichment of TiSi2 crystals.

Effect of Cu Addition on Microstructure and Hardness of As-Cast and Heat-Treated High-Cr Cast Iron

The objective of the present study is to investigate the effect of Cu addition on microstructure and hardness of hypoeutectic high-Cr cast irons (26 wt% Cr) in as-cast and heat-treated conditions. As-cast specimens with varying amount of copper (Cu) addition were produced using an industrial grade high-frequency induction furnace. As-cast specimens were heat-treated in a box furnace using a typical reversed heat treatment sequence where subcritical heat treatment was followed by destabilization heat treatment. Microstructural analysis of the as-cast and heat-treated specimens was carried out using an optical microscope and Feritscope to understand the effect of Cu addition on the microstructure. The bulk hardness of all the specimens was measured using a Brinell hardness tester. The obtained result shows that the microstructures of the as-cast specimens mostly consist of austenitic dendrite matrix with γ+ M7C3 eutectic colony morphology. The eutectic colony consists of fine carbides in the central region and coarse carbides at the boundary region. High Cu containing specimen has a higher amount of thin rod-like M7C3 carbides, whereas low Cu containing specimen has a higher fraction of massive carbide morphology. Heat-treated specimens with various Cu content show mixed microstructure mostly consisting of retained austenite, transformed martensite, eutectic carbides, and secondary carbides. However, their relative volume fraction changes with the change in Cu content. Hardness result shows that higher Cu containing specimen has a lower hardness than the lower Cu contain specimens for both as-cast and heat-treated conditions. Although heat-treated specimens, in general, have higher hardness values than the as-cast specimens.

Reaction between MgO-SiO2 refractory material and Fe-Al alloy

The interaction between molten Fe-Al alloy containing 5.1 wt.% aluminium and MgO-SiO2-based refractory was investigated. In high-frequency induction furnace at 1550 °C refractory samples were immersed in liquid alloy for 1 min, 2 min, 10 min, 20 min, 30 min and 60 min. Scanning electron microscope was employed to investigate phases at the interface and inclusions in the Fe-Al alloy. Forsterite phase in refractory was transformed to MgO·Al2O3 spinel, owing to the reduction of iron oxide and silica in forsterite by aluminium in the Fe-Al alloy at the interface. The interface layer separated locally from the refractory material and formed cluster and single particles in the Fe-Al alloy. In view on the reaction rate, the disintegration of the refractory material increased the reaction area but interfered with increasing thickness of the spinel layer. The dissolution rate of silica into the molten alloy decreased with increasing the reaction time because of the slowed down transport of aluminium diffusing through increasing spinel layer became the rate controlling step.

CePd2Ga3 and CePd2Zn3 – Kondo lattices and magnetic behaviour

We report the single crystal properties of CePd2Zn3 and CePd2Ga3 compounds. The compounds were prepared by Bridgman method in high-frequency induction furnace. Both compounds adopt the hexagonal PrNi2Al3-type structure with a = 5.3914(2) Å, c = 4.3012(2) Åfor CePd2Zn3 and a = 5.4106(8) Å, c = 4.2671(8) Åfor CePd2Ga3, respectively. CePd2Zn3 orders antiferromagnetically below TN = 1.9K. Magnetoresistance measurements revealed a crossover at Bc = 0.95T. CePd2Ga3 orders ferromagnetically at TC = 6.7K. Applied hydrostatic pressure reduces the value of the Curie-temperature (rate ∂TC/∂p=0.9 KGPa −1) down to 3.9K at 3.2GPa. Both compounds display a strong magnetocrystalline anisotropy with easy axis of magnetization perpendicular to the c-axis in the hexagonal lattice.

Determination of Total Sulfur, Sulfate, Sulfite, Thiosulfate, and Sulfolipids in Plants.

In response to oxidative stress the biosynthesis of the ROS scavenger, glutathione is induced. This requires the induction of the sulfate reduction pathway for an adequate supply of cysteine, the precursor for glutathione. Cysteine also acts as the sulfur donor for the sulfuration of the molybdenum cofactor, crucial for the last step of ABA biosynthesis. Sulfate and sulfite are, respectively, the precursor and intermediate for cysteine biosynthesis and there is evidence for stress-induced sulfate uptake and further downstream, enhanced sulfite generation by 5'-phosphosulfate (APS) reductase (APR, EC 1.8.99.2) activity. Sulfite reductase (SiR, E.C.1.8.7.1) protects the chloroplast against toxic levels of sulfite by reducing it to sulfide. In case of sulfite accumulation as a result of air pollution or stress-induced premature senescence, such as in extended darkness, sulfite can be oxidized to sulfate by sulfite oxidase. Additionally sulfite can be catalyzed to thiosulfate by sulfurtransferases or to UDP-sulfoquinovose by SQD1, being the first step toward sulfolipid biosynthesis.Determination of total sulfur in plants can be accomplished using many techniques such as ICP-AES, high-frequency induction furnace, high performance ion chromatography, sulfur combustion analysis, and colorimetric titration. Here we describe a total sulfur detection method in plants by elemental analyzer (EA). The used EA method is simple, sensitive, and accurate, and can be applied for the determination of total S content in plants.Sulfate anions in the soil are the main source of sulfur, required for normal growth and development, of plants. Plants take up sulfate ions from the soil, which are then reduced and incorporated into organic matter. Plant sulfate content can be determined by ion chromatography with carbonate eluents.Sulfite is an intermediate in the reductive assimilation of sulfate to the essential amino acids cysteine and methionine, and is cytotoxic above a certain threshold if not rapidly metabolized and can wreak havoc at the cellular and whole plant levels. Plant sulfite content affects carbon and nitrogen homeostasis Therefore, methods capable of determining sulfite levels in plants are of major importance. Here we present two robust laboratory protocols which can be used for sulfite detection in plants.Thiosulfate is an essential sulfur intermediate less toxic than sulfite which is accumulating in plants in response to sulfite accumulation. The complexity of thiosulfate detection is linked to its chemical properties. Here we present a rapid, sensitive, and accurate colorimetric method based on the enzymatic conversion of thiosulfate to thiocyanate.The plant sulfolipid sulfoquinovosyldiacylglycerol (SQDG) accounts for a large fraction of organic sulfur in the biosphere. Aside from sulfur amino acids, SQDG represents a considerable sink for sulfate in plants and is the only sulfur-containing anionic glycerolipid that is found in the photosynthetic membranes of plastids. We present the separation of sulfolipids from other fatty acids in two simple ways: by one- and two-dimensional thin-layer chromatography.

Multiphase steel with improved impact-abrasive wear resistance in comparison with conventional Hadfield steel

In the present work, a new multiphase steel and a conventional Hadfield steel (Mn13Cr2) were investigated after being casted in a high-frequency induction furnace. Field-emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and thermal dilatometer were applied to characterize impact-abrasive wear behaviors, wear mechanisms and phase transformation of the two steels. Results revealed that the multiphase steel with a triplex microstructure (bainite, martensite and retained austenite) had higher tensile strength, micro-hardness and impact-abrasive wear resistance than Mn13Cr2. The main strengthening mechanisms were phase transformation (retained austenite to martensite), grain refinement and high density dislocations for the multiphase steel, and the interaction of twining and dislocation walls were for Mn13Cr2, respectively. The wear mechanisms of the multiphase steel were called as “press-in particle”, “micro-voids” and “delaminated crater”, however those of Mn13Cr2 were called as “adhesion”, “crater” and “micro-crack”. Impact-abrasive wear features like grain deformation, orientated features, crack propagation, voids linking and the block effect of bulk retained austenite to crack branching were observed in the affected layer of the multiphase steel.

Enhanced Air Stability in REPb3 (RE = Rare Earths) by Dimensional Reduction Mediated Valence Transition.

We conceptually selected the compounds REPb3 (RE = Eu, Yb), which are unstable in air, and converted them to the stable materials in ambient conditions by the chemical processes of "nanoparticle formation" and "dimensional reduction". The nanoparticles and the bulk counterparts were synthesized by the solvothermal and high-frequency induction furnace heating methods, respectively. The reduction of the particle size led to the valence transition of the rare earth atom, which was monitored through magnetic susceptibility and X-ray absorption near edge spectroscopy (XANES) measurements. The stability was checked by X-ray diffraction and thermogravimetric analysis over a period of seven months in oxygen and argon atmospheres and confirmed by XANES. The nanoparticles showed outstanding stability toward aerial oxidation over a period of seven months compared to the bulk counterpart, as the latter one is more prone to the oxidation within a few days.

Primary Fragmentation Characteristics of Coal Particles during Rapid Pyrolysis

Experiments were carried out to investigate the rapid pyrolysis of Nei-meng (NM) lignite, Shen-fu (SF) bituminous coal, and Jin-cheng (JS) anthracite with the duration time of 0–500 ms and the temperature of 1173–1773 K using a high-frequency induction furnace. Interest was centered on the primary fragmental characteristics of particles, including the changes of mass loss, particle density, and size distribution, during the pyrolysis. A pair of fragmental parameters, i.e., dimensionless particle diameter δ and particle distribution Sf, was proposed to characterize the fragmentation during the different stages of pyrolysis. The result showed that the pyrolysis progress increases with time and temperature. The fragmentation extent is also positively related to the time and temperature. The progress of primary fragmentation is lignite ≈ bituminous coal > anthracite. However, the particle morphology changes little during the pyrolysis fragmentation. Evidence reveals that major fragmentations of NM and SF occu...