High Frequency Induction Heating Research Articles

Hot Bending–Quenching Characteristics of Heat Treatable A6063 Aluminum Tubes

This study investigates the application of hot bending–quenching technology to heat-treatable A6063 aluminum tubes, focusing on the bending formability and mechanical properties after aging treatment under various heating conditions. High-frequency induction heating was used to uniformly heat aluminum tubes to the solution treatment temperature of 560 °C. The effect of wall thickness on bending formability was explored, revealing that thinner tubes (2 mm) experienced significant flattening defects, whereas thicker tubes (5 mm) exhibited superior formability with reduced shrinkage and wall thinning. Additionally, the pre-quenching temperature was found to influence the mechanical properties of the tube with a thickness of 5 mm. Tubes held at the solution temperature for 1 min 30 s or longer maintained higher temperatures during transfer, resulting in improved tensile strength and hardness after aging. The findings confirm the feasibility of applying hot bending–quenching technology to aluminum tubes, though careful control of temperature loss during continuous industrial processes is required to ensure optimal mechanical performance.

A Novel LCLC Parallel Resonant Circuit for High-Frequency Induction Heating Application

A Novel LCLC Parallel Resonant Circuit for High-Frequency Induction Heating Application

Investigation on titanium wire melting through high-frequency induction heating for additive manufacturing process

ABSTRACT A high-frequency induction heating (HFIH) system is a novel and clean heat source that can potentially melt high melting point material to develop the wire feed-based additive manufacturing (AM) process. The present study establishes the optimised coil parameters, including coil geometry for melting the titanium wire using induction heating. A fully coupled electromagnetic-thermal-fluid flow model is established to analyse the temperature profile of the wire. The wire feed velocity (0.012 m/s) is incorporated in the coupled model using the deformed mesh method. Optimised wire diameter and coil parameters, such as a three-turn helical coil with a circular cross-section, coil turn spacing of 1.5 mm, and a coupling distance of 4 mm, melt the 3.6 mm titanium wire rapidly and create the molten droplet. The results suggest that the optimised coil parameters improve the magnetic flux density, which enhances joule heating in the wire. However, the conical-spiral coil geometry of the three-turn fails to melt the wire completely. In contrast, the helical coil of the three-turn melts the wire completely. The maximum velocity of the molten metal is found as 0.25 m/s. Effectively, the heat transfer and material flow analysis drives to develop the potential additive manufacturing system.

Induction assisted autogenous plasma arc welding of HSLA steel

In this work, a high frequency induction heating (HFIH) assisted plasma arc welding (IPAW) technique is proposed to weld 6 mm thick S690QL high strength low alloy steel plates in square butt joint configuration and without using any filler material. A 3D finite element based coupled electromagnetic-thermal analysis is carried out to ascertain the weld's thermal characteristics. Microstructure evolution and mechanical performance are investigated using scanning electron microscopy, electron back scattered diffraction, transmission electron microscopy, tensile test, Charpy impact test and micro hardness test. The results demonstrate that 15 s initial static heating using a co-directional current coil with magnetic flux concentrator predominantly improves the weld penetration by 48 % and joint efficiency reaches 90 % to the base plate strength. Microstructural study shows that the addition of HFIH promotes low angle grain boundaries (LAGB) with bainite ferrite and granular bainite micro-constituents in the fusion zone, which causes localised yielding and failure in this zone during tensile test. Further investigation reveals that the HFIH encourages the formation of BI-type bainite ferrite laths of 1.3–2.2 μm width, combined with slender martensite-austenite (M-A) island at the bainite ferrite lath boundaries. The results also reveal that the induction heating promotes the formation of M23C6 precipitates and B2 structured Cu-enrich nano precipitates in the fusion zone (FZ). The microhardness distribution indicates that the FZ and coarse grain heat affected zone are significantly reduced due to the assistance of the HFIH. The impact test result shows a lower energy absorption by the IPAW weldments due to dominance of the LAGB with unfavourable strain distribution.

Preparation of Al-Li-Cu-Graphite Composite via High-Energy Ball Milling and Sintering with High-Frequency Induction Heating

Preparation of Al-Li-Cu-Graphite Composite via High-Energy Ball Milling and Sintering with High-Frequency Induction Heating

Research on erosion wear behavior of NiTi alloy coating fabricated via high-frequency induction heating technology

NiTi alloy is widely used in extreme working conditions due to its pseudoelasticity, shape memory effect and wear resistance. In this study, the NiTi alloy coating (Ni49.8Ti50.2 (at%)) was fabricated by high-frequency induction heating. The coating was well-formed on the surface of cemented carbide YG8 and converted to crystalline after aging treatment. The results of 70h erosion wear experiments carried on the rotary erosion wear test device showing that the erosion wear amount of the coating was reduced by 93 % compared with that of YG8, resulting from the deformation recovery effect. Moreover, the main erosion wear mechanism of the coating was micro-cutting and ploughing. This study can provide technical support and theoretical basis for preparing of NiTi alloy coating and erosion wear resistance.

The effect of fibers addition on the microstructure and mechanical properties of ZrO2 fibers toughened Al2O3/ZrO2 (Y2O3) solidified ceramics

Fiber toughening is considered an effective way to strengthen the toughness of traditional sintered ceramics. Herein, ZrO2 fibers toughened Al2O3/ZrO2 (Y2O3) directionally solidified eutectic ceramics (DSECs) were prepared with the high-frequency induction heating zone melting (IHZM). The effects of ZrO2 fibers content on the phase composition, microstructure, and mechanical properties of the eutectic ceramics were studied. The findings revealed that DSEC consists of α-Al2O3 and ZrO2 phases, presents a typical colony microstructure. The phase spacing in the colony decreased with the addition of fibers, reaching a minimum value of 1.99 ± 0.25 μm at 20 wt%, which was nearly 40 % lower than that without the fiber’s addition. The hardness of DSEC increased gradually with the addition of fibers. Its highest value reaches 18.42 ± 0.55 GPa when the fiber content is 20 %. The fracture toughness of DSEC first increased and then decreased, reaching a maximum of 5.43 ± 0.22 MPa·m1/2 at 10 wt%, which was 1.5 times higher than that of the fibers-free eutectic ceramic. The improvement of fracture toughness was primarily due to the fibers toughening. In addition, the crack deflection, pinning, bridging, and branching had a significant inhibitory effect on the crack propagation.

Validation of 3D and 2D thermal and electromagnetic models for high-frequency induction heating in crystal growth processes

Induction heating is crucial to various crystal growth techniques, including the Floating Zone (FZ) method, which is used for producing high-quality single silicon crystals. In this work, 3D and 2D axisymmetric numerical models for the high-frequency induction heating in the FZ process are implemented in open-source software tools Elmer and OpenFOAM. The models are compared and validated with in-situ measurements conducted on a model experiment of the FZ process, consisting of a flat inductor that heats a tin rod. The magnetic flux density distribution around the inductor is measured using a 3D induction coil probe, and the rod’s surface temperature is measured using an infrared camera. Both numerical models were found to be in good agreement with the experimental data, with deviations mainly due to geometric approximations and simplified thermal modeling. The present measurement setup can be used as a benchmark for other numerical models of high-frequency induction processes.

In-situ synthesis and oxidation behaviors of Ti-xAl coatings by high-frequency induction heated combustion

Ti-xAl coatings (x=25, 33.3, 50, 66.7, and 75 at%) were fabricated in situ using high-frequency induction heating synthesis (HFIHCS). The process parameters for preparing Ti-Al coatings via HFIHCS were orthogonally optimized employing the finite element method. The effect of the aluminum content on the microstructures and phase compositions of Ti-Al coatings fabricated by HFIHCS, as well as their oxidation behaviors at 900℃ for 100 h was investigated. The results showed that the distribution of interfacial temperature difference was influenced by induced current (62.11%), relative density of compact (9.86%), and indenter material (28.03%). The minimum interfacial temperature difference was achieved with an induced current of 300 A, a graphite indenter material, and a compact density of 82.9%. The Ti-xAl coatings exhibited a core (Ti)-shell (TixAly) ring structure. The rise in aluminum content in the Ti-xAl coatings led to a gradual reduction in the titanium-rich phase, accompanied by a progressive increase in the aluminum-rich phase and the interface thickness of zones Ⅰ and Ⅱ. The porosities of Ti-xAl coatings containing over 50 at% aluminum exhibited an order of magnitude higher than those of Ti-xAl coatings with 50% aluminum or lower. The mechanisms of reaction, pore-forming, and interfacial diffusion for Ti-xAl coatings were predominantly controlled by dissolution-precipitation, thermal expansion of intrinsic pores within the cold-pressed compact and voids formed after molten aluminum flow, and liquid-solid co-diffusion, respectively. The increase in aluminum content in the Ti-xAl coatings led to in a gradual decrease in its oxidative weight gain, a shift in the oxidation kinetics from a linear-parabolic to a parabolic law, and an enhancement in preservation of internal core-shell characteristics and the likelihood of forming a protective layer of thin Al2O3. The oxidation behaviors of Ti-xAl coatings with a core-shell structure were co-controlled by the aluminum content and the porosity affected by the aluminum content.

Fabrication of Titanium Aluminide Alloys by Twin-Wire Tungsten Inert Gas Welding Applied with High-Frequency Induction Heating Wire Technology: Processing, Microstructure, and Properties

Fabrication of Titanium Aluminide Alloys by Twin-Wire Tungsten Inert Gas Welding Applied with High-Frequency Induction Heating Wire Technology: Processing, Microstructure, and Properties

Optimization of composition, cold rolling scheme and structure of brass strip workpiece for continuous high-frequency pressure welding

The influence of thickness, deformation scheme, grain size and chemical composition of annealed Л68 alloy strip billet on the quality of tubes for continuous pressure welding after high-frequency induction heating are analyzed. Two methods are considered for obtaining of billets for welding of tubes from brass alloyed with silicon, ensuring high quality tubes. Keywords:tube, brass, high-frequency welding, workpiece, weld seam, chemical composition mikhailpevzner@yandex.ru

Influence of the sintering method on microstructure and microhardness of AlCuNiSnZn-based high-entropy brasses and bronzes obtained by powder metallurgy

The present report focused on synthesizing and characterizing a series of AlCuNiSnZn alloys obtained by powder metallurgy as a new family of high-entropy brasses and bronzes. The (AlCuNi)80Sn10Zn10 and (AlCuNi)70Sn15Zn15 alloys were obtained by mechanical alloying and sintering, evaluating two sintered methods: high-frequency induction heat and conventional. After 10 h of mechanical alloying, the elemental powder mixture formed solid solutions of face-centered cubic (FCC-α) and body-centered cubic (BCC-β) phases. However, the solid solutions, after sintering, were decomposed into a mixture of γ Ni2Zn11, AlNi, and Cu2Ni3Sn3 phases. The (AlCuNi)80Sn10Zn10 system sintered by high-frequency induction heat exhibits a microhardness value of ∼501 HV±17, while that obtained by the conventional method was ∼320 ± 21 HV. The results showed that it is convenient to maintain the BCC/FCC solid solutions after sintering due to their stability and properties. In addition, it is necessary to design alloys with lower values of ΔHmix to improve the microhardness.

Numerical simulation and experimental study on the preparation of the inner layer of bimetal composite pipe by high-frequency induction heating

Bimetal composite pipe has the advantages of impact resistance, low thermal expansion rate, pressure resistance and high temperature resistance. Its application scope is becoming more and more extensive, bringing more obvious economic, environmental and social benefits. In order to explore a new process for preparing bimetal composite pipe that is green, energy-saving and efficient. Ansys Workbench and Maxwell were used for joint simulation to obtain process parameters such as temperature distribution and thermal conduction time during high-frequency induction heating. Then the preparation of the bimetal composite pipe was completed through experiments, the forming quality and mechanical properties of the inner layer were tested and analyzed. The results show that process parameters have a significant impact on the molding quality of the inner layer. By optimizing the parameters, an amorphous inner layer with good molding quality, high hardness and high toughness was prepared, forming a metallurgical bond with the base pipe, with a bonding strength of 90.6 MPa. This research can provide a guidance for the preparation of bimetal composite pipe by high-frequency induction heating.

A Study on Defect Detection of Dissimilar Joints in Cu-STS Tubes Using Infrared Thermal Imaging of Induction Heating Brazing

We proposed a novel detection method for identifying joint defects in the brazing process between copper tubes and stainless steel using a convolutional neural network (CNN) model. The brazing joints were created using high-frequency induction heating equipment, and infrared thermal imaging cameras were employed to capture the thermal data generated during the jointing process. The experiments involved 15.88 mm diameter copper tubes commonly used in plate heat exchangers, stainless-steel tubes, and filler metal containing 20% Ag. The thermal data were obtained with a resolution of 80 × 80 pixels per frame, resulting in 4796 normal joint data and 5437 defective joint data collected over 100 high-frequency induction-heating brazing experiments. A total of 10,233 thermal imaging data were categorized into 6548 training data, 1638 validation data, and 2047 test data for the development of the predictive model. We designed CNN models with varying hyperparameters, specifically the number of kernel filters and nodes, to evaluate their impact on detection performance. A comparative analysis revealed that a CNN model structure, exhibiting 98.53% accuracy and 99.82% recall on test data, was the most effective. The selected CNN-based defect prediction model demonstrated the potential of using CNN models to discern joint defects in tube configurations that are challenging to identify visually. This study opens avenues for applying CNN-based models for detecting imperfections in complex tube structures.

Fast Synthesis of Fine Boron Carbide Powders Using Electromagnetic Induction Synthesis Method

Boron carbide (B4C) powders with defined stoichiometry, high crystallinity, minimal impurity content, and a fine particle size are imperative for realizing the exceptional properties of this compound in advanced high-technology applications. Nevertheless, achieving the desired stoichiometry and particle size using traditional synthesis methods, which rely on prolonged high-temperature processes, can be challenging. The primary objective of this study is to synthesize fine B4C powders characterized by high crystallinity and a sub-micron particle size, employing a fast and energy-efficient method. B4C powders are synthesized from elemental boron and carbon in a high-frequency induction heating furnace using the electromagnetic induction synthesis (EMIS) method. The rapid heating rate achieved through contactless heating promotes the ignition and propagation of the exothermic chemical reaction between boron and carbon. Additionally, electromagnetic effects accelerate atomic diffusion, allowing the reaction to be completed in an exceptionally short timeframe. The grain size and crystallinity of B4C can be finely tuned by adjusting various process parameters, including the post-ignition holding temperature and the duration of heating. As a result, fine B4C powders can be synthesized in under 10 min. Moreover, these synthesized B4C powders exhibit oxidation onset temperatures higher than 500 °C when exposed to air.

Rapid processes for the production of nanocrystal yttria-stabilized tetragonal zirconia polycrystalline ceramics: ultrasonic spray pyrolysis synthesis and high-frequency induction sintering

In this study, nanocrystalline 3 mol % yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) ceramic was produced by sintering with a high-frequency induction heating (HFIH) system of granular powders obtained by ultrasonic spray pyrolysis (USP) at 600 °C. The granular nano-sized powders (10-30 nm) were micron in size (average size: 700 nm), spherical in shape and amorphous. The influences of the HFIH sintering temperature (1400-1600 °C), applied current time (60-300 sec.) and the mechanical pressure (10 MPa and 20 MPa) on the final density and grain size of the products were investigated. The amorphous granular Y-TZP powders compressed with the HFIH system allow very rapid condensation in the tetragonal phase at high density and avoid grain growth. High density (relative density over 95) nanocrystalline Y-TZP ceramic with ∼70 nm size could be obtained from the simultaneous application of 20 MPa pressure and an induced current within 300 sec. of sintering time at 1500 °C. In this condition, the sample’s maximum hardness and fracture toughness values were reached at 14.9 GPa and 3.8 MPa·m1/2, respectively. Y-TZP powders produced in nano-micro structure with the USP system were sintered with the HFIH system and rapid production was achieved by preventing grain growth.

Study on physical property regulation and high-temperature heat storage properties of Al–Si composite phase change materials prepared by one-step pressing

In this paper, we investigate a metal composite prepared using a one-step pressing method, where Al–Si alloy acts as the phase change materials (PCMs) and Al2O3/AlN serve as the structural support materials. The alloy formation and PCM composite preparation are synthesized in a single step. The study aims to characterize the microstructure, thermodynamic, and thermal properties of the composite material. To assess the heat storage properties of the prepared composite PCMs at temperatures higher than 600 °C, a high-temperature test system is established using a high-frequency induction heater. Additionally, we explore how to improve the issue of liquid leakage under high-temperature conditions. The results demonstrate that Al2O3 and AlN (ceramic materials) exhibit excellent chemical compatibility with Al–Si composite PCMs. After sintering, the ceramic materials form a strong bond with Al–Si, effectively retaining the liquid phase of Al–Si alloy within the composite material. Consequently, the Al–Si composite PCMs do not exhibit high-temperature liquid leakage under elevated conditions. Both Al2O3/Al–Si and AlN/Al–Si composites possess favorable high temperature heat storage properties. The phase change enthalpy of Al2O3/Al–Si composite reaches 400 kJ/kg, with a thermal conductivity of 36 W/(m·K). Similarly, the AlN/Al–Si composite achieves a phase change enthalpy of 404 kJ/kg and a thermal conductivity of 43 W/(m·K). Both composites fulfill the requirements for high-temperature heat storage applications.

Mechanical and Microstructural Characteristics of 1.5 GPa-Grade Boron Steel by High-Frequency Induction of Eddy Currents

In the automobile industry, high-strength plates are increasingly used to reduce vehicle weight due to strict regulations on fuel efficiency and safety, and these plates achieve a tensile strength of 1500 MPa due to the hot-stamping process. Recently, research has been conducted to examine the flow behavior of materials according to the relationship between hot stamping time-temperature characteristics, coil shape, cooling method, and thermodynamic flow characteristics of quenching materials. In this study, a basic experiment in the form of a plate was conducted using an eddy current generated during high-frequency induction heating. It presents the surface temperature change, mechanical characteristics, and microstructure of boron steel that has undergone a high-frequency induction heating process. Surface temperature data were analyzed at different high-frequency induction heating forces (15, 18, 21, 24, 27, and 30 kW) and distances from specimens (6, 9, 12, and 15 mm). Two phases, austenite and ferrite, were formed in the low-temperature region, and martensite was formed in the high-temperature region. Mechanical properties and microstructures were also analyzed under different high-frequency induction heating coil conditions. The correlation between the high-frequency induction heating force and the specimen with the maximum tensile strength was investigated. Due to high-frequency induction heating, scale generation and surface decarbonization can be avoided. As a result of this experiment, 1500 MPa of the same tensile strength as the mechanical characteristics obtained in the existing heat treatment could be obtained.

Microstructural stability and high temperature strength of directionally solidified Al2O3/Er3Al5O12/ZrO2 eutectic ceramics

Al2O3/Er3Al5O12(EAG)/ZrO2 directionally solidified eutectic ceramics (DSECs) were prepared with high frequency induction heating zone melting (IHZM), and heat treated at high temperature. Their phase components, microstructures, flexural and tensile strengths were investigated. The results indicated that the microstructures were composed of the mutually interpenetrated Al2O3, EAG and ZrO2 (stabilized by Er3+ ion) phases. As the growth rate increased from 2 mm/h to 20 mm/h, the phase size decreased and the irregular microstructure became regular. When the heat treatment temperature was up to 1400 °C, the ionic diffusion was triggered and the phase began to grow. Under the action of surface energy and special microstructure, the growth of phase stopped after it reached a certain threshold. The sample with smaller phase size exhibited higher strength at room temperature, which was dependent on the crack propagation resistance. However, the speed of strength reduction was faster. The formation of surface groove, microcrack and malignant growth phase was responsible for this rapidly decreasing of strength. The flexural and tensile strengths of eutectic ceramic with larger phase size remained at 671.6 MPa and 359.45 MPa after long-term heat treatment at 1500 °C, respectively. The smaller difference between the original phase size and the maximum coarsened phase size was beneficial to avoid the occurrence of the above mentioned harmful factors and was the source of strength stability.

Innovative technologies for strengthening of internal surfaces of suspension parts of heavy-loaded machines by laser and high-frequency induction methods

In the article innovative methods of surface hardening of internal surfaces of machine parts by laser and highfrequency induction heating are presented. The relevance of applying the methods of laser and induction hardening for the internal surfaces of heavily loaded parts of quarry equipment is proved. The results of modeling and calculation of thermal and electromagnetic fields under the influence of an external electromagnetic field and laser radiation beams are presented. The original design of a complex of equipment for processing the internal surfaces of suspension parts by external electromagnetic field is described. The optimal designs of inductors with magnetic circuits made of various materials are shown. The study of the structure and properties obtained on the internal surfaces of heavily loaded suspension parts of cars, line of the BelAZ company, treated according to the optimal modes of surface induction exposure is given. The developed original technology and equipment of laser surface hardening, which makes it possible to increase the wear resistance of heavily loaded parts, is described. Data on the implementation of research results at JSC “BELAZ” – the Management Company of the Holding “BELAZ-HOLDING” for processing a wide range of heavily loaded suspension parts are given.