Egbert Baake

High-frequency induction (HFI) tube welding is an energy-intensive process in which the impeder plays a critical role in power utilization. Conventional ferrite cores often operate near magnetic saturation in small-diameter applications, which can limit efficiency and process stability, particularly under high production rates. Soft magnetic composites (SMCs) offer higher saturation potential, but their internal behavior under welding conditions is difficult to assess experimentally. To address this challenge, this study proposes a methodology for evaluating impeder performance without relying on industrial-scale trials. The approach combines a three-dimensional electromagnetic–thermal model of the welding process with a reduced two-dimensional model for detailed analysis. The predictive capability of the 3D model was assessed through comparison with experimental measurements, providing an initial experimental validation under the investigated operating conditions. Based on this reference, a 2D model is derived by removing the tube and introducing an equivalent correction factor, obtained through comparison with the 3D results, to account for its influence. The reduced model is then used to investigate the internal thermal behavior of a representative SMC (Fluxtrol 50) impeder. The results reveal a pronounced hotspot in the region corresponding to the inductor position, with significantly higher temperatures than in other areas, indicating a critical thermal limitation for operation. The proposed methodology provides a reliable and efficient framework for analyzing and designing impeder systems, offering a practical alternative to costly industrial testing.

Industrial production still relies heavily on thermal processes that predominantly use fossil fuels for energy. This has significant consequences for primary energy use and greenhouse gas emissions. Meanwhile, rapid advances in electrotechnologies—defined as processes that use electrical energy to transform materials through internal heat dissipation (inductive, conductive, or dielectric/microwave) or heat transfer via resistance and infrared systems—are paving the way for a transition to a non-fossil fuel-based energy supply across a wide range of temperatures and power densities. However, replacing fuel with electricity is not simply a case of making a straightforward substitution; the feasibility of this change is determined by process requirements, constraints on installation space and grid connection, the reliability and volatility of the electricity supply, and economics. This paper therefore proposes a simple, decision-oriented methodology to assess the feasibility of defossilisation from energetic and economic perspectives. The methodology centres on a “substitution coefficient” that compares the amount of fossil energy substituted by a given amount of electrical energy and benchmarks this against the primary energy intensity of electricity generation. The methodology is demonstrated using case studies from energy-intensive sectors such as cement production (using resistance and microwave methods), steel strip processing (with inductive boosting combined with resistive holding) and metal melting for cast iron and aluminium. The case studies show under which conditions electrification can be implemented as a drop-in substitute, a hybrid booster or an enabler of new production models. The results indicate where electrotechnologies can deliver primary energy savings and CO₂ reductions today and outline the conditions under which their advantages will increase as power systems become more decarbonised.

Non steady applied magnetic field impact on a liquid metal has good prospects for industry. For a better understanding of heat and mass transfer processes under these circumstances, numerical simulations are needed. A combination of finite elements and volumes methods was used to calculate the flow and solidification of liquid metal under electromagnetic influence. Validation of numerical results was carried out by means of measuring with ultrasound Doppler velocimetry technique, as well as with neutron radiography snapshots of the position and shape of the solid/liquid interface. As a result of the first part of the work, a numerical model of electromagnetic stirring and solidification was developed and validated. This model could be an effective tool for analyzing the electromagnetic stirring during the solidification process. In the second part, the dependences of the velocity pulsation amplitude and the melt velocity maximum value on the magnetic field pulsation frequency are obtained. The ability of the pulsating force to develop higher values of the liquid metal velocity at a frequency close to the MHD resonance was found numerically. The obtained characteristics give a more detailed description of the electrically conductive liquid behaviour under action of pulsating traveling magnetic field.

The paper describes the results of an experimental research, demonstrating and explaining the effect of grain fragmentation, caused by pulsed resonant electromagnetic stirring. In the experiments, 6082 aluminium alloy melt was directionally solidified under the influence of continuous (AMF) and pulsed application (PMF) of an alternating magnetic field. The frequency of applied PMF was in accordance to the low-frequency circulation of the melt, causing the resonant increase of a pulsed component of the melt velocity. The structure of electromagnetically stirred specimens was compared to those, solidified without a magnetic field. A strong fragmentation effect (decrease of an average grain size on 51%, comparing with the solidification in natural conditions) for the case of resonant EM stirring was stated. Further, to analyse the influence of the flow, appearing due to the resonant stirring, we observed the formation of solid/liquid interface and a macro-crystalloid structure during solidification of continuously and pulsed stirred melt by applying the novel method of neutron radiography. The results confirmed the strong influence of the pulsed component of velocity on thermal conditions during solidification and, consequently, the metal structure.

This article contains findings of simulation research on longitudinal induction welding of cladded pipes with use of simultaneous double frequency. Solutions are proposed to reach the required temperature distribution at the welding edge for the cladding composite of S355 and Alloy 625 with single and simultaneous double frequency. An advanced consideration of magnetic and other material properties was performed to simulate the dominating physical effects of high frequency (HF) welding. The background of use and advantages of simultaneous double frequency are presented. In the context of the research, a correlation for welding speed, frequency and temperature distribution with industrial relevance was found for the cladded pipe welding.

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The paper describes the results of two experimental investigations aimed to extend the abilities of a neutron radiography to visualize two-phase processes in the electromagnetically (EM) driven melt flow. In the first experiment the Argon bubbly flow in the molten Galliuma simulation of the CO 2 free production of Hydrogen processwas investigated and visualized. Abilities of EM stirring for control on the bubbles residence time in the melt were tested. The second experiment was directed to visualization of a solidification front formation under the influence of EM field. On the basis of the neutron shadow pictures the form of growing ingot, influenced by turbulent flows, was considered. In the both cases rotating permanent magnets were agitating the melt flow. The experimental results have shown that the neutron radiography can be successfully employed for obtaining the visual information about the described processes.

Purpose: The purpose of this paper is to research a multi-zone rubber vulcanization process heated by induction. Design/methodology/approach: The design is an abstract setup model with two zones, where the homogene rubber compound is heated with different regimes. Simulation is completely done in ANSYS Mechanical by the finite element method solution. The research is made mostly simulative. Findings: The results show that it is possible to obtain a factor-three vulcanization level difference in a core of a 20-mm rubber plate in a distance of less than 60 mm, while the heating is done from the side of the surface. Originality/value: The originality is the combination of rubber vulcanization with a dynamic heat source in a form of electromagnetic induction applied on the mold form. This allows a high level of control of the vulcanization process of the rubber compound.

Purpose: The purpose of this paper is to the study the multiphase bubbles flow motion in a vertical channel with an electroconducting liquid without and under the influence of a magnetic field. Design/methodology/approach: For numerical calculations, the lattice Boltzmann method (LBM) is used, which is based on the kinetic theory for solving fluid mechanics and other physical problems. The phase-field lattice Boltzmann model is developed to simulate the behaviour of multiphase bubble–bubble interaction while rising in the fluid with high density ratios. Findings: The behaviour of the rising bubble flow in a rectangular column of two phases is investigated with the two-dimensional LBM. Originality/value: The multiphase flow in electroconducting liquids with high ratio of density is studied using the LBM.