High Frequency Induction Heating Research Articles

The Influence of Grade P6M5 Tool Steel Induction Nitriding Process Parameters on the Diffusion Layer Microhardness and Thickness

The effect the inductor current and the duration of thermal exposure in a nitrogen medium have on the microhardness and depth of the diffusion layers formed in grade P6M5 steel is studied. The investigation was carried out on 5-mm-thick samples 10 mm in diameter that had not been subjected to preliminary heat treatment. The samples were nitrided in a specially designed chamber in the form of a sealed quartz vessel placed in an inductor. The steel samples were placed in the chamber at the inductor location level. After filling the chamber with nitrogen gas to a pressure of 0.2±0.05 MPa, the samples were subjected to high-frequency induction heating. The temperature of the samples was adjusted by changing the inductor current from 4.8 to 5.8 kA. It was found that at an inductor current of 4.8 kA, the sample was heated to a temperature above 800°C; with a further increase in the current, the sample temperature increased above 1000°C. As a result of nitriding with a duration of 300–1200 s at a temperature of 800–1000°C, a surface nitride layer with a thickness of up to 20 μm and a diffusion sublayer with a thickness of up to 200 μm were produced. The surface layers were characterized by a nitrogen content of up to 9 at % and microhardness of 1930–1950 HV (200 gf). The diffusion layers were characterized by a lower nitrogen content of up to 6 at %. and microhardness of 1450–1500 HV (100 gf). Based on the obtained experimental data, empirical models describing the effect of the inductor current and the duration of thermal exposure on the diffusion layer thickness and microhardness have been developed.

Research On Designing Workpiece Loading Robot for High Frequency Induction Heating Machine in Production Facilities in Vietnam

This paper presents a part of the results of research on designing and building a workpiece loading robot for the high-frequency induction heating machine in the production facilities in Vietnam. The robot is used to load 12-kilogram cylindrical steel workpieces, the working length of its arm is 500 mm with an accuracy of ± 1 mm. The robot is designed in 3D based on kinematic analysis and tested for operation in a real production condition. The study is conducted in order to automate the heating-steel process, improving productivity and reducing manpower in the production facilities in Vietnam.

Fabrication of flame-retardant magnesium alloy hollow sphere with specific gravity less than one through atmospheric foaming

Metallic hollow sphere is a kind of lightweight metal foams. Most metallic hollow spheres have been made of iron. The authors have succeeded to fabricate Mg-Al-Zn alloy hollow spheres through inert gas foaming in the previous study. In the present study, magnesium alloy hollow spheres are fabricated through atmospheric foaming. The starting material was AZX912 flame-retardant magnesium alloy plates. AZX912 alloy precursors were produced through accumulative diffusion-bonding process. Magnesium hydride powder with the total amount of 1.0 mass% was used as a foaming agent. Foaming tests were carried out in atmosphere using a high-frequency induction heating system. The foaming process was in-situ observed by the digital video camera. The AZX912 alloy precursor expanded with increasing the heating time. As a result, AZX912 alloy hollow sphere with the porosity of 50% was obtained successfully. The hollow sphere easily floated on the surface of water because of the specific gravity of 0.91 and the closed-cell structure.

Modeling and Simulation of a Novel Neural PLL controller for Circuit of Series Resonant Inverter in High Frequency Induction Heating

Wydawnictwo SIGMA-NOT wydaje czasopisma fachowe informujące swoich czytelników o najnowszych osiągnięciach naukowych i nowoczesnych rozwiązaniach technicznych w Polsce i na świecie, popularyzuje problemy techniczne oraz poszerza wiedzę i kulturę techniczną.

Critical conditions for melting of metallic wire in induction heating system through numerical simulation and experiments

Induction heating is a novel energy source that can be utilized in the melting of metallic wires for the development of green manufacturing processes such as drop-casting and additive manufacturing. The present work aims to find out the critical radius of the feedstock wire to be melted through an induction heating system. An analytical model is developed to find an initial assessment of the feasible parameters and assists the 3D coupled electromagnetic-thermal model to study the melting behaviour of the mild steel wire. Through these models, the time required to reach the melting point of the wire for various process conditions has been investigated. The coil current and the number of turns of the coil primarily influence the melting duration of the wire. The experiments on a high-frequency induction heating system suggests that the critical wire size of 1.6 mm transfer the metal droplets at 550 A coil current, 15 mm inner coil radius, 3-turn induction coil and 353 kHz frequency. At this point, the finite element model acts as an aid to develop the experimental system and provides satisfactory results when compared with experimental data. This work effectively presents a mathematical framework where critical size of wire is identified to create molten droplets in a specific induction heating system.

Microstructure and Mechanical Properties of Vacuum Centrifugal Casted Ti-6Al-4V Alloy by Casting and Heat Treatment

The Ti-6Al-4V alloy has been widely used for structural materials due to high specific strength property, however it is difficult to cast because of high reactivity at high temperature. In this study casting characteristics and post-casting heat treatment were studied in the cast Ti alloy. The cast alloy was prepared using high-frequency induction heating and horizontal vacuum centrifugal casting to reduce reaction with crucible and mold by minimizing overheating of the molten metal and casting fast. In the thin casting with a thickness of 2 mm, α’ martensite was observed, and in the casting with a thickness of 4~8 mm, α+β Widmanstätten was observed. As the thickness of the casting increased, the grain size, α-lath width, and α-case thickness increased. Accordingly, as the thickness of the casting increased, the hardness of the matrix decreased and the hardness of the surface increased. In addition, when the casting was heat treated below the β-phase transformation temperature, the α-lath width increased, and when quenched after heat treatment in the β-phase transformation temperature region, an α’ martensite was formed. On the other hand, when the casting was heat treated in the atmosphere, it was confirmed that the elongation was very low because hydrogen and oxygen in the atmosphere were induced. In addition it was confirmed that casting defects can be removed through HIP.

Simple Lossless Inductive Snubbers-Assisted Series Load Resonant Inverter Operating under ZCS-PDM Scheme for High-Frequency Induction Heating Fixed Roller

This paper presents a high-frequency pulse-density-modulated (PDM) soft-switching series load resonant inverter for use in induction heating (IH) fixed roller applications, which is used in copy and printing machines. The proposed simple high-frequency resonant inverter uses an asymmetrical pulse pattern PDM control scheme to achieve complete zero-current soft-switching commutations over a wide output range of input power regulation. Additionally, when the printer toner requires operation in very light load conditions, this causes difficulty in achieving zero-voltage or zero-current soft-switching operations in the IH high-frequency resonant inverters with pulse frequency modulation or pulse width modulation control schemes. The proposed resonant inverter demonstrates the capability to accomplish highly efficient power conversions. In this work, a fixed roller for printing machines is developed for doing experiments to verify the efficiency of the proposed circuit topology and its PDM control schemes. The inverter’s steady-state and transient operating principles are analyzed based on the proposed control strategy at a high-frequency PDM. Operating conditions such as power loss analysis, power conversion efficiency and temperature rise characteristics of the proposed inverter are presented and analyzed through experimental results. Finally, from a practical viewpoint, a comparative study of a conventional halogen lamp heater and the proposed IH fixed roller is deliberated.

Harmonics Suppression of AC Source Current of a Single Phase Source Fed Induction Heating System

Any high frequency Induction heating system while undergoing through very high frequency switching operations, produces Electromagnetic Interference (EMI) noises or very high frequency harmonics within the system. These high frequency EMI noises conductively propagate towards the input AC source and distort the sinusoidal input AC current and make it non-sinusoidal. The desired performance from the induction heating cannot be anticipated. As such, it is inevitable to eliminate such EMI noises from the input AC source current to get the desired performance. Here, a specially designed ring type LC low pass passive filter is proposed which can accomplish to suppress these high frequency EMI noises up to satisfactory level and can restore the sinusoidal shape in the input AC source current waveform and thus improves the power quality of the AC supply for the induction heating system. The impact of the induction heating system without and with incorporating the proposed filter will be compared in this study.

Two-time Calibration at Both Ends for Sulfur Measurement by Using High Frequency Induction Infrared Absorption Method

High frequency induction heating infrared absorption method is a relative measurement method, and it requires calibrating the analyzer during the measurement process. Usually, one-time calibration on an analyzer is made for high sulfur value by using standard substances. The method proposed by this paper calibrates carbon-sulfur analyzers with a method of two-time calibration at both ends, which eliminates the impact of sulfur blank and thus improves the accuracy and precision of ultra-low sulfur measurement. The method extents the lower limit of measurement of sulfur in high temperature alloy, to 0.00005%, namely, 0.5ppm.

Experimental investigation on the coolability of nuclear reactor debris beds using seawater

During the Fukushima nuclear reactor accident, seawater was injected into the reactor core to cool the decay heat from the heat generating porous debris bed. However, the impact of dissolved salts in water on the coolability of a debris bed is not well understood. This paper is one of the first works to investigate the cooling mechanisms for debris bed using seawater. An experimental system was built where the packed bed test section was volumetrically heated via a high frequency induction heater. The temperature along the axis of the test section was measured using a high resolution temperature sensor based on Optical Frequency Domain Reflectometry. Experimental results show that the dryout heat flux increases with an increase in concentration, with pure water having a dryout volumetric heat flux of 1.8 MW/m3 and salt water of concentration 7% having a dryout volumetric heat flux of 2.8 MW/m3. However, this enhanced coolability using salt water is short term, as the crystallization fouling mechanism becomes significant over time and leads to gradual temperature excursion in the bed. The fouling mechanism eventually leads to a cross section of the debris bed to plug with the deposited salts, and this leads to a pressure build up in the lower regions of the debris bed.

Design, Analysis and Experimental Verification of the Self-Resonant Inverter for Induction Heating Crucible Melting Furnace Based on IGBTs Connected in Parallel

The object of this research was a self-resonated inverter, based on paralleled Insulated-Gate Bipolar Transistors (IGBTs), for high-frequency induction heating equipment, operating in a wide range of output powers, applicable for research and industrial purposes. For the nominal installed capacity for these types of invertors to be improved, the presented inverter with a modified circuit comprising IGBT transistors connected in parallel was explored. The suggested topology required several engineering problems to be solved: minimisation of the current mismatch amongst the paralleled transistors; a precise analysis of the dynamic and static transistors’ parameters; determination of the derating and mismatch factors necessary for a reliable design; experimental verification confirming the applicability of the suggested topology in the investigated inverter. This paper presents the design and analysis of IGBT transistors based on datasheet parameters and mathematical apparatus application. The expected current mismatch and the necessary derating factor, based on the expected mismatch in transistor parameters in a production lot, were determined. The suggested design was experimentally tested and investigated using a self-resonant inverter model in a melting crucible induction laboratory furnace.

Synthesis and Sintering of Nanostructured ZrB2-SiC Composite

ZrB2 is considered a candidate material for ultra-high temperature ceramics because of its high thermal conductivity, high melting point, and low coefficient of thermal expansion. Despite these attractive properties, applications of ZrB2 are limited by its low fracture toughness below the brittle-ductile transition temperature. To improve its ductile properties, the approach universally utilized has been to add a second material to form composites and fabricate nanostructured materials. One example of this is the adding of SiC to ZrB2 to improve fracture toughness. SiC has low density, excellent resistance to oxidation in air, and a high melting point. Therefore, SiC may be a promising additive as a reinforcing material for ZrB2-based composites. A dense nanostructured ZrB2-SiC composite was rapidly synthesized and sintered by high-frequency induction heating (HFIH) within 4 min in one step, from mechanically activated powders of ZrC, 2B and Si. Simultaneous combustion synthesis and consolidation were accomplished using the combination of current and mechanical pressure. A highly dense ZrB2-SiC composite with a relative density of up to 98.4% was fabricated using the simultaneous application of 70 MPa pressure and an induced current. The mechanical properties (toughness and hardness) and the average grain size of the composite were investigated.

Balanced Mechanical and Tribological Performance of High-Frequency-Sintered Al-SiC Achieved via Innovative Milling Route—Experimental and Theoretical Study

In this study, Al-SiC nanocomposite was fabricated via powder metallurgy route using different innovative high-energy ball-milling techniques (HEBM). The powder mixture was consolidated using high-frequency induction heat sintering process (HFIHS). With the aim of studying the physical, mechanical, and tribological performance of the fabricated nanocomposites. Relative density, hardness, compressive yield strength, Young’s modulus, toughness, elongation, specific wear rate and coefficient of friction were experimentally investigated. A finite element model for the frictional process was built to find out the distribution of contact stresses as result of samples sliding. It was found that the highest the energy of the milling, the more improvement in the mechanical and tribological performance could significantly achieved due to the homogeneous distribution and the excellent bonding effect of the composite. In addition, field emission scanning electron microscope was used for studying the sliding surface morphology in order to explicate the mechanism of the dry wear process.

Evaluation of Weakening Characteristics of Reinforced Concrete Using High-Frequency Induction Heating Method

To increase the quality of recycling, a new demolition technique is required that can work in parallel with existing crushing methods, which use large equipment with high crushing efficiency. Moreover, the efficient collection of the remains from the fractional dismantling method needs to be considered based on its procedure, and the technology for partial dismantling that is efficient in remodeling, maintenance, and reinforcement has to be developed. In this study, the temperature-increasing characteristics of rebars inside ferroconcrete with respect to their arrangement was investigated by partial rapid heating through high-frequency induction heating. Based on this, the chemical and physical vulnerability characteristics of ferroconcrete due to the thermal conduction generated on the rebar surface and the cracks caused by the thermal expansion pressure of the rebar were verified. In addition, the objective of this study was to verify the applicability of the technology by specifying the vulnerability range of ferroconcrete based on the heating range with adequate consumption of energy.

A Study on the Heat and Stress Evaluation of Reinforced Concrete through High-Frequency Induction Heating System Using Finite Element Techniques

In this study, we analysed the thermal field generated on the surface of reinforcing steel through 2D and 3D magnetic field analyses based on previous experiments on the temperature rise characteristics of reinforcing steel, temperature rise characteristics and mechanical characteristics. According to the results of the analysis of transferred heat from heated reinforcing steel to concrete, the actual reinforced concrete was analysed and compared with the actual measurements, and the following conclusions were reached. Through analysing the heat source that is generated by the eddy current and the heat that is transferred from the reinforcing steel to concrete, stress analysis is expected to predict and evaluate various problems that arise when induction heating technology is applied to the site.

Evaluation of Heating Technique of Deformed Reinforcement Using High-Frequency Induction Heating System

To improve recycling quality, it is necessary to develop a demolition technology that can be combined with existing crushing methods that employ large shredding-efficient equipment. The efficient collection of bones in a segmentation dismantling method must be considered according to the procedure. Furthermore, there is a need for the development of partial dismantling technologies that enable efficient remodeling, maintenance, and reinforcement. In this study, we experimentally investigated the temperature-rise characteristics of reinforced concrete through partial rapid heating during high-frequency induced heating. Accordingly, the chemical and physical vulnerability characteristics of the reinforced concrete were verified by studying the thermal conduction on the surface of the rebars and the cracks caused by the thermal expansion pressure of the rebars. Furthermore, we aimed to verify the applicability of the proposed technology by specifying the vulnerability range of the reinforced concrete based on the heating range, as well as the appropriate energy consumption. We investigated the temperature rise and temperature distribution characteristics of the rebar surfaces based on diameter, length, bar placement conditions, heating distance, heating coil location, and output, using reinforced steel of grade SD345. Maximum powers of 5, 6, and 10 kW, and inductive heating were used to achieve satisfactory results.

EXPERIMENTAL INVESTIGATION OF SPRINGBACK OF LOCALLY HEATED ADVANCED-HIGH STRENGTH STEELS

Sheet metal bending is one of the important metals forming processes at ambient temperature. The usage of high-strength steel is one of the stronger materials for the construction of components in the automotive industries. However, for complex shapes, cold forming is not always sufficient, and heating the workpiece plays a major role in manufacturing these shapes. Bendability may increase with increasing forming temperature and currently, hot forming of advanced high strength steels (AHSS) is becoming more attractive. While hot forming of AHSS is beneficial for high formability, subsequent quenching is required to maintain final strength. This procedure extends the production time. In this study, temperature gradients, bending loads, and springback after V-bending were investigated. The experimental study was carried out on a 2 mm thick Docol 1500M steel at various temperatures by using a speed-controlled servo press machine. The bending regions of the specimens were locally heated to 200, 300, 400, 500, and 600oC by using a high-frequency induction heating device. The results show that; punch loads were significantly lowered with increasing the local heating temperature during bending. There were no cracks observed on the specimens. The amount of spring back is decreasing with the bending temperature and around 500oC almost no springback was measured. Negative spring back was observed for the bending temperatures higher than 500oC

Indirect Temperature Measurement in High Frequency Heating Systems.

One of the biggest challenges of fused deposition modeling (FDM)/fused filament fabrication (FFF) 3D-printing is maintaining consistent quality of layer-to-layer adhesion, and on the larger scale, homogeneity of material inside the whole printed object. An approach for mitigating and/or resolving those problems, based on the rapid and reliable control of the extruded material temperature during the printing process, was proposed. High frequency induction heating of the nozzle with a minimum mass (<1 g) was used. To ensure the required dynamic characteristics of heating and cooling processes in a high power (peak power > 300 W) heating system, an indirect (eddy current) temperature measurement method was proposed. It is based on dynamic analysis over various temperature-dependent parameters directly in the process of heating. To ensure better temperature measurement accuracy, a series-parallel resonant circuit containing an induction heating coil, an approach of desired signal detection, algorithms for digital signal processing and a regression model that determines the dependence of the desired signal on temperature and magnetic field strength were proposed. The testbed system designed to confirm the results of the conducted research showed the effectiveness of the proposed indirect measurement method. With an accuracy of ±3 °C, the measurement time is 20 ms in the operating temperature range from 50 to 350 °C. The designed temperature control system based on an indirect measurement method will provide high mechanical properties and consistent quality of printed objects.

Preliminary Study on Electromagnetic Thermal Coupling Numerical Simulation Technology of Static Inductor

In this paper, the load transfer analysis method is used. Firstly, the magnetic thermal coupling analysis model is established and the material parameters are determined in ANSYS software. Secondly, the direction of applied current is determined by studying the influence of current direction on the temperature field in the electrified wire. Then, the relationship between current frequency, current magnitude and temperature field and the change of temperature at typical points with time are studied respectively. Finally, the parameters of temperature field for high frequency induction heater to produce better plastic deformation are determined. The research content of this paper can provide a reference for the subsequent research of electromagnetic thermal structure coupling numerical simulation technology of mobile inductor.

Increase of the mechanical response of pure aluminum by grain refinement retained with an alternative rapid sintering route

High-frequency induction heating is frequently used to consolidate solid pieces of refractory ceramics. However, this valuable technique has not been deeply evaluated for sample preparation in light metal-based systems as an economical and feasible alternative for rapid sintering routes such as spark plasma sintering. This work deals with the potential use of induction heating to produce highly densified samples with refined microstructure, enhanced mechanical properties, and lower oxygen contamination. Here we demonstrate that induction-sintering can increase the hardness and yield strength in 70 and 80% respectively, compared to a commercial hardened alloy (AA-1350-H19). Theoretical calculations demonstrate that this behavior can be attributed to two main reinforcement mechanisms: dislocations obstruction and grain refinement. The increased mechanical response can be imputed to the effective sub-micron microstructure retention due to its shorter processing time and lower temperature compared to the conventional sintering process.