High Frequency Induction Heating Research Articles

Thermal stability of nanocrystalline Al−10Fe−5Cr bulk alloy

Abstract Thermal stability of nanocrystalline Al−10wt.%Fe−5wt.%Cr bulk alloy was investigated. The initial micro-grained mixture of powders was processed for 100 h using mechanical alloying (MA) to produce nano-grained alloy. The processed powders were sintered using high frequency induction heat sintering (HFIHS). The microstructures of the processed alloy in the form of powders and bulk samples were investigated using XRD, FESEM and HRTEM. Microhardness and compression tests were conducted on the bulk samples for evaluating their mechanical properties. To evaluate the thermal stability of the bulk samples, they were experimented at 573, 623, 673 and 723 K under compression load at strain rates of 1×10−1 and 1×10−2 s−1. The annealed samples exhibited a significant increase in their microhardness value of 2.65 GPa when being annealed at 723 K, as compared to 2.25 GPa of the as-sintered alloy. The bulk alloy revealed compressive strengths of 520 MPa and 450 MPa at 300 K and 723 K, respectively, when applying a strain rate of 1×10−1 s−1. The microstructural stability of the bulk alloy was ascribed to the formation of iron and chromium containing phases with Al such as Al6Fe, Al13Fe4 and Al13Cr2, in addition to the supersaturated solid solution (SSSS) of Cr and Fe in Al matrix.

Separation behavior of metal-resin composite film using high frequency induction heating

Waste flexible printed circuit (WFPC) contains a number of precious resources such as base and noble metals. In this research, we propose a new separation / recovery technology using high frequency induction heating as a recycling process of WFPC. The peeling strength of the sample heated by high frequency induction heating was quantitatively evaluated using a tensile tester, and the effect of sample dimensions and heating conditions on adhesive properties was experimentally investigated. As a result of the high frequency induction heating experiment, it became clear that the coil current when the FPC simulated sample is peeled decrease with increase in heating area and decrease in sample thickness. As a result of the tensile test, there was a difference in peeling behavior between the unheated sample and the heated sample. It was found that the peeling tensile force of the heated sample increased with increase in the coil current. In addition, the peeling tensile force showed a tendency to decrease after reaching the maximum. Ultimately, the peeling tensile force of the sample heated at the critical current value was decrease than that of the unheated sample.

Evaluation of Continuous Welding Behavior of CFRTP Using High-Frequency Induction Heating

Evaluation of Continuous Welding Behavior of CFRTP Using High-Frequency Induction Heating

Microhardness Improvement of Ni-W/SiC Composite Coatings by High Frequency Induction Heat Treatment

Electrodeposited Ni-W alloy coating is considered as one of the most suitable candidate to replace the environmentally hazardous hexavalent hard chromium coatings. However, it is necessary to carry out heat-treatment at a high temperature to improve its microhardness and refine its grain. In the present work, an alternative high frequency induction heat-treatment (HFI-HT) technology was used to improve surface microhardness of Ni-W/SiC composite coatings, which were electrodeposited from an ammonium-citrate bath, containing suspended green SiC particles. Transformation of amorphous to crystalline structure can be observed after HFI-HT. The precipitation of a Ni6W6C phase rather than a Ni4W phase occurs by prolonging induction time to 64 s at a power density of 21 W mm−2 or turning power density up to 42 W mm−2 for 4 s. While the two phases of Ni6W6C and Ni4W can be precipitated at 900°C. The microhardness of Ni-W/SiC composite coatings can be improved up to 1100 HV with HFI-HT at 21 W mm−2 for 8 s, which is comparable to that of hard chrome coatings.

High-Frequency Induction Heating of Al-Si-Cu-Mg aluminum alloy in Thixoforming

Thixoforming is the process of shaping near net shape metal components in a semisolid state. The process consists of preparing feedstock, reheating and shaping. Reheating the billet is the most critical step in thixoforming. Induction heating requires precise temperature control to obtain globular microstructure and prevent process defects, such as insufficient heating, overheating, and electromagnetic end effect and elephant foot phenomena. Moreover, inductive heating parameters are investigated to improve the quality of thixoforming. This study investigates applied coil current and optimal coil geometry and design (i.e. height, diameter and coil turn) in high-frequency induction heating numerically and experimentally. Simulation results combined with an approximation approach method are verified via a reheating experiment. The proposed method validated via an experiment can be a practical tool for predicting temperature distribution and reheating time required for thixoforming.

Synthesis and Rapid Consolidation of W-1.5 ZrO2 Composite

ZrO2 is a candidate material for hip and knee joint replacements because of its excellent combination of biocompatibility, corrosion resistance and low density. However, the drawback of pure ZrO2 is a low fracture toughness at room temperature. One of the most obvious tactics to cope with this problem is to fabricate a nanostructured composite material. Nanomaterials can be produced with improved mechanical properties(hardness and fracture toughness). The high-frequency induction heated sintering method takes advantage of simultaneously applying induced current and mechanical pressure during sintering. As a result, nanostructured materials can be achieved within very short time. In this study, W and ZrO2 nanopowders are mechanochemically synthesized from WO3 and Zr powders according to the reaction(WO3 + 3/2 Zr→W+ 3/2 ZrO2). The milled powders are then sintered using high-frequency induction heating within two minutes under the uniaxial pressure of 80MPa. The average fracture toughness and hardness of the nanostructured W-3/2 ZrO2 composite sintered at 1300°C are 540 kg/mm2 and 5 MPa·m1/2, respectively. The fracture toughness of the composite is higher than that of monolithic ZrO2. The phase and microstructure of the composite is also investigated by XRD and FE-SEM.

Tribological Investigation of Multilayer Graphene Reinforced Alumina Ceramic Nanocomposites

We investigated the wear resistance properties of high-frequency induction heat (HFIH) sintered alumina (Al2O3) ceramic nanocomposites containing various multilayer graphene (MLG) concentrations. The tribology of the monolithic Al2O3 and nanocomposites samples was assessed against spherical ceramic (Si3N4) counter sliding partner at sliding loads ranging from 6 to 40 N using ball-on-disk wear test configuration. Compared with the monolithic Al2O3, the incorporation of 1.0 vol % MLG reduced the friction coefficient by 25% and the wear rate by 65% in the MLG/Al2O3 nanocomposites tested under 40 N sliding load. Based on the mechanical properties, brittle index, and microstructure, the active wear mechanisms for the nanocomposites were analyzed. The MLG contributed in the nanocomposites tribology process, indirectly, by enhancing the mechanical properties and, directly, by reducing the friction between the counter sliding partners. The synergistic role of MLG thin triboflim and twirled MLG for improving the tribological performance of the nanocomposites is discussed.

Induction Heating Technology for Steel Wire Processing

This article discusses the induction heating application features in metallurgical industry for previously unused objects, such as wire coils and wire rod bundles. The analysis of international trends and a forecast of the induction heating application shows a steady expansion of the induction technologies in the metallurgical industry. The article considers the advantages of induction heating in comparison to other competitive technologies. Heat treatment in electrotechnological induction plants is determined by the interconnected electric and thermophysical processes taking place in them, the complex nature of the internal heat sources distribution, the dependence of the distribution pattern of the induction plant on the temperature of the products being processed. It is shown that the investigation results of the induction heating method influence the temperature and time factors in the formation of the structure, the increase in the uniformity of heating, and the quality of the heat treatment of steel wire and wire rod buntle, taking into account the stated technological task. The efficiency estimation of application of medium and high-frequency induction heating of steel wire of various diameters is given. Evaluation of the efficiency improving of the induction heating device, when the heat treatment simultaneous multiple strands of steel wire of equal diameter, united in a bundle, is given.

The Effect of the Green Density on the Properties of Powder Metallurgy Ti Sintered by High Frequency Induction Heating

Sintering is a vital technology used for consolidation of metal and ceramic powders. The process is generally long and energy consuming because of the way in which heat transfer happens in electrical and gas furnaces. This study focuses on optimizing the sintering process of metallic powders, in particular titanium, using high frequency induction heating as alternative sintering method. Using electromagnetic induction and the associated Eddy current effect, the heat is generated directly into the electrically conductive object. Consequently, faster heating rates and lower heat loses are achieved. The purpose of this study is to understand the effect of process parameters, such as the powder compact density, on the efficiency of the induction heating and the properties of the sintered materials. The average heating rates recorded while heating to 1300oC are in the range of 3.5o to 15.3o C per second. Significant densification and consolidation, evident by the amount of closed porosity and increase in tensile strength was found in spite of the short heating time. The results show that the powder compact density plays a crucial role on the heating efficiency as well on the properties of the sintered material such as final density, porosity distribution and tensile properties. The samples with higher initial density showed tensile strength and ductility values comparable to those of high vacuum sintered and those specified by international standards for powder metallurgy Ti products.

Complex Crystal Chemistry of Yb6(CuGa)50 and Yb6(CuGa)51 Grown at Different Synthetic Conditions

Two new compounds in the Yb–Cu–Ga system were discovered. Yb6(CuGa)50 was obtained as single crystals grown from gallium metal flux, and Yb6(CuGa)51 was synthesized by high-frequency induction heating technique. Structure analysis reveals new structure type for Yb6(CuGa)50 (C2/m space group), while Yb6(CuGa)51 crystallizes in rhombohedral space group R3̅m adopting the Th2Zn17 structure type. Both structures could be derived from the simplest layered packing, through CaCu5-type structure, as a common parent. Physical properties of the Yb6(CuGa)51 sample obtained bulk quantity were explored. The magnetic susceptibility study of Yb6(CuGa)51 in the temperature range of 2–300 K suggests a valence fluctuation at lower temperatures. X-ray absorption near edge spectroscopy suggests that Yb exists in mixed-valent state in Yb6(CuGa)51. Electrical resistivity measurement reveals that Yb6(CuGa)51 is metallic in nature and shows Fermi-liquid behavior in the temperature range from 3.5 to 25 K.

Effect of bonding conditions on the bonding strength in an aluminum bonding using ultrasonic vibrations and high-frequency induction heating in an atmosphere

ABSTRACTThe needs of aluminium joints have grown in recent years. However, as aluminium forms strong oxide layers on the surface in an atmosphere, joining of these materials is difficult. This is why we conceived a new atmosphere solid-phase bonding method that uses high-frequency induction heating and ultrasonic vibration. The effects of ultrasonic vibration and bonding conditions on this new bonding method were investigated. As a result, we were able to confirm the efficacy of ultrasonic waves on bonding. The bonding mechanism of new bonding method was also clear.

Residual stresses of polycrystalline CBN abrasive grits brazed with a high-frequency induction heating technique

Residual stresses produced in polycrystalline CBN abrasive grits during a high-frequency induction brazing process are calculated by using finite element analysis, with a consideration of the nonuniform temperature distribution in the induction brazing model. The influences of induction brazing parameters on the residual stresses of polycrystalline CBN abrasive grits have been analyzed, including the embedding depth, grit side length, etc. Results obtained show that the tensile stress with a 40% embedding depth is 292 MPa, which is the minimum on the bonding interface compared with other embedding depths. Meanwhile, the maximum tensile stress is 575 MPa, with an increase of 59% compared with that of a grit side length of 50 mm. Finally, the simulation results of the brazing residual stress of polycrystalline CBN abrasive grits have been confirmed valid based on the residual stress measurement of the brazed monocrystalline CBN grit.

Thermal Load Test Method and Numerical Calculation for Ceramic Matrix Composite Turbine Guide Vane

With the improvement of inlet temperature of aero-engine turbine, continuous fiber reinforced ceramic matrix composite (CFCC) has become an important material for turbine guide vane. In this paper, the testing method of steady state thermal load and cyclic thermal load were explored under typical working environment of turbine guide vane. The temperature field was established through the high-frequency induction heating and was measured by thermocouples and an infrared thermometer. The DIC strain gauge was used to measure the strain. This method overcomes the difficulties in the temperature field establishment, temperature and strain measurements of the ceramic matrix composites. The material mapping method has been applied to calculate the macroscopic stress and strain. It has been observed that the maximum strain error was 11.8% compared with the steady state thermal load experiment result. On this basis, the stress and strain of the thermal fatigue load were analyzed. In addition, a fatigue test was carried out on the standard test pieces, which had the same manufacturing process with the turbine vane. The obtained results through this paper show that the life of the vane was more than 8.34 × 106 under the thermal fatigue load. The experimental and numerical calculation methods proposed in this study provide the experimental and theoretical basis for further research.

Enhancement of Electrical Property of Thermally-Annealed Nano Carbon Based Polymer Composite By High Frequency Induction Heating

It has been said that CNT and Graphene have especially excellent electrical, thermally and mechanical property. Also it has been expected as fillers for polymer composite instead of conventional carbon fiber. Recently large amount of research has been done about Nanocarbon, so we can get easily a lot of kind of Nanocarbon. There is not the universal standard for Nanocarbon materials especially CNT and Graphene. Therefore, it causes a large problem for prediction of property of composites that their qualities and size are not uniform because property and structure of CNTs are changed by production method. CNTs has different names and property depending on the number of layers such as Single-wall carbon nanotube (SWCNT) and Multi-wall carbon nanotube (MWCNT). So the purpose in this study is to clarify the effect of Nano carbon materials quality on the properties of polymer based Nanocarbon composite and to develop polymer matrix Nanocarbon composite which have excellent properties. We improve the quality by heating the Nanocarbon materials in the inert atmosphere by high frequency induction heating. Also we compared filler properties of Nanocarbon composite polymer. First, the sample of CNT and Graphite was set into a carbon crucible and heated in the inert atmosphere for 10 to 30 minutes by high frequency induction heating. Thereafter, the qualities of the annealed samples were analyzed by Raman spectroscopy. In Raman spectroscopy can analyze crystal integrity, diameter and other. In the Raman scattering spectrum of CNT appear characteristic waveforms. Specifically, it are appeared near 1590 cm⁻¹ called G band and near 1350 cm⁻¹ called D band. Since the G band is derived from the in-plane stretching motion of the 6-membered ring structure of carbon atoms in graphite and the D band is derived from its defect structure, the crystal integrity (G / D ratio) is determined by the ratio of the peaks of the G band and the D band . In general, the larger the G / D ratio is, the higher the crystalline perfection is. For example, when graphene is thermally annealed at 1500 ° C for 15 minutes, the Full Width at Half Maximum (FWHM) is larger than that of without thermally annealing. It showed that impurities in graphite were removed by thermal annealing. But, there was not large change in G/D ratio. Second, the shapes of samples were analyzed for example diameter and length by using a scanning electron microscope. In SEM observation, the shape and size of Nanocarbon was mainly observed. TEM mainly observed the diameter, size and layers of CNT. Next, the nanocarbon samples were mechanical mixing with the polymer. This matrix used polypropylene (PP).The mixer used was of an elliptical blade. The temperature was 200 to 250 ° C. for 30 to 60 minutes, and the rotation speed was 80 to 100 rpm. Finally, the volume resistivity of the prepared composite material was measured using a resistivity meter. In general, the volume resistivity of PP is about 10 ^ 16 to 10 ^ 17 Ωcm, and the boundary through which electricity passes is said to be 10 ^ 6 Ωcm. Also, we think that annealed high quality Nanocarbon property in comparison with no thermal annealed Nanocarbon. So, we will be able to improve property of Nanocarbon composite.

Growth and Scintillation Properties of Two-Inch-Diameter SrI2(Eu) Single Crystals

The sealed vertical Bridgman (VB) method is the main technique used to grow SrI2(Eu) crystals because SrI2(Eu) is very hygroscopic. In this study, we grew SrI2(Eu) single crystals with two-inch diameters and four-inch lengths using the VB method equipped with a removable chamber. The SrI2(Eu) single crystals were produced by the Liquinert process, which requires careful consideration of the crucible material and growth atmosphere. After a review of available materials, carbon crucibles were selected due to their several advantages over traditional quartz ampules: (1) they are suitable for large size crystal growth due to which they do not require any process for sealing of quartz ampule before the growth; (2) ease in controlling the temperature gradient because carbon crucibles can be heated directly via a high frequency induction heating system; and (3) carbon crucibles can assist in removing oxygen and moisture from the melt. The starting material, seed, and hot zone were prepared inside the glovebox in...

Thermophysical Properties of High-Frequency Induction Heat Sintered Graphene Nanoplatelets/Alumina Ceramic Functional Nanocomposites

This paper concerns the thermophysical properties of high-frequency induction heat (HFIH) sintered alumina ceramic nanocomposites containing various graphene nanoplatelets (GNP) concentrations. The GNP/alumina nanocomposites demonstrated high densities, fine-grained microstructures, highest fracture toughness and hardness values of 5.7 MPa m1/2 and 18.4 GPa, which found 72 and 8%, superior to the benchmarked monolithic alumina, respectively. We determine the role of GNP in tuning the microstructure and inducing toughening mechanisms in the nanocomposites. The sintered monolithic alumina exhibited thermal conductivity value of 24.8 W/mK; however, steady drops of 2, 15 and 19% were recorded after adding respective GNP contents of 0.25, 0.5 and 1.0 wt.% in the nanocomposites. In addition, a dwindling trend in thermal conductions with increasing temperatures was recorded for all sintered samples. Simulation of experimental results with proven theoretical thermal models showed the dominant role of GNP dispersions, microstructural porosity, elastic modulus and grain size in controlling the thermal transport properties of the GNP/alumina nanocomposites. Thermogravimetric analysis showed that the nanocomposite with up to 0.5 mass% of GNP is thermally stable at the temperatures greater than 875 °C. The GNP/alumina nanocomposites owning a distinctive combination of mechanical and thermal properties are promising contenders for the specific components of the aerospace engine and electronic devices having contact with elevated temperatures.

Feasibility of Multipoint Press with Continuously Divisional Forming for Double Curvature Plates in Shipbuilding

This article introduces a mechanical forming technique using a set of multipoint press forming (MPF) steps to obtain a curved hull plate. Given only the geometry of the desired surface, the integrated MPF system can generate the punch strokes required by various geometries of hull surfaces without the need for solid dies. The divisional MPF-forming technique can form double-curvature surfaces since the discrete die surface is constructed by changing the strokes of the double-sided reconfigurable multiple presses. The spring-back phenomena after unloading can be successfully compensated for by a combination of finite element analysis (FEA) and the displacement adjustment method. The deformation history of a moving plate on each division was simulated while carefully considering the movement toward a contacting boundary. The displacement adjustment iterates the calculation of punch strokes based on the deformed geometry simulated by FEA, which was used to simulate the spring-back of the plate. The strokes are determined by an iterative process of sequential pressing. A nonlinear shell element was used to deal with the elasto-plastic state and contact problems at the tool-metal interfaces. The appropriate stroke is calculated for each punch for both the initial and corrective forming processes. Experiments were performed to validate the configuration of the spring-back compensation, divisional forming and the integrated system. The predicted punch stroke in the displacement adjustment shows good agreement with the experimental results. 1. Introduction The bow and stern sections of a ship have double-curvature surfaces, whereas the parallel midship section is characterized by flat and cylindrical plates. Double-curvature surfaces are currently formed using the line heating method, in which the forming quality and geometrical precision depend on the thermal elasto-plastic deformation behavior. Gas-flame and high-frequency induction heating have been successfully used to provide the heat needed for thermal bending (Shin et al. 2003; Shin & Lee 2002; Nomoto et al. 1990; Jang et al. 2002). However, it is difficult to control the residual deformation of thermal bending because it is not easy to control the plastic strain distribution, which is coupled with the heat input.

Single Stage Boost Integrated High-Frequency Full Bridge Inverter for Induction Heating System

This paper proposes a new single-stage boost high frequency ac series resonant power inverter for high frequency induction heating (IH) applications. The proposed ac-ac converter consist of a single stage boost (SSB) converter and full-bridge ac series resonant inverter integrated circuit with a ac source voltage control strategy by controlling the inverter switches. The Simulink model is developed using MATLAB simulation software and the simulated results are examined. The output power is maintained to the required level by using phase shift control strategy and the simulated results are validated.

Microstructural Evaluation of Inductively Sintered Aluminum Matrix Nanocomposites Reinforced with Silicon Carbide and/or Graphene Nanoplatelets for Tribological Applications

Silicon carbide (SiC) nanoparticles (NP) and/or graphene nanoplatelets (GNP) were incorporated into the aluminum matrix through colloidal dispersion and mixing of the powders, followed by consolidation using a high-frequency induction heat sintering process. All the nanocomposite samples exhibited high densification (> 96 pct) with a maximum increase in Vickers microhardness by 92 pct relative to that of pure aluminum. The tribological properties of the samples were determined at the normal frictional forces of 10 and 50 N. At relatively low load of 10 N, the adhesive wear was found to be the predominant wear mechanism, whereas in the case of a 50 N normal load, there was significant contribution from abrasive wear possibly by hard SiC NP. From wear tests, the values for the coefficient of friction (COF) and the normalized wear rate were determined. The improvement in hardness and wear resistance may be attributed to multiple factors, including high relative density, uniform SiC and GNP dispersion in the aluminum matrix, grain refinement through GNP pinning, as well as inhibition of dislocation movement by SiC NP. The nanocomposite sample containing 10 SiC and 0.5 GNP (by wt pct) yielded the maximum wear resistance at 10 N normal load. Microstructural characterization of the nanocomposite surfaces and wear debris was performed using scanning electron microscope (SEM) and transmission electron microscope (TEM). The synergistic effect of the GNP and SiC nanostructures accounts for superior wear resistance in the aluminum matrix nanocomposites.

Microstructure and Mechanical Properties of Al₂O₃/Er₃Al₅O12 Binary Eutectic Ceramic Prepared by Bridgman Method.

Directionally solidified Al2O3/Er3Al5O12 (EAG) eutectic ceramic was prepared via vertical Bridgman method with high-frequency induction heating. The effects of the growth rate on the microstructure and mechanical properties of the solidified ceramic were investigated. The experimental results showed that there were no pores or amorphous phases in the directionally solidified Al2O3/EAG eutectic ceramic. Al2O3 phase was embedded in the EAG matrix phase, and the two phases were intertwined with each other to form a typical binary eutectic “hieroglyphic” structure. With the increase of growth rate, the phase size and spacing of the solidified Al2O3/EAG ceramic both decreased, and the growth rate and phase spacing satisfied the λ2v ≈ 60 formula of Jackson-Hunt theory. The cross section microstructure of the solidified ceramic always exhibited an irregular eutectic growth, while the longitudinal section microstructure presented a directional growth. The mechanical properties of the solidified ceramic gradually increased with the increase of growth rate, and the maximum hardness and fracture toughness could reach 21.57 GPa and 2.98 MPa·m1/2 respectively. It was considered that the crack deflection and branching could enhance the toughness of the solidified ceramic effectively.