Electric Arc Energy Research Articles

Multi-regional microstructure control using ultrasonic-assisted directed energy deposition for Al-Cu alloy

The uneven microstructure and element distribution between the inner-layer zone (INZ) and the inter-layer zone (ITZ) resulting from the thermal cycling effect during the directed energy deposition process with the electric arc energy source (DED-Arc) can lead to inferior mechanical properties. In order to address this problem, the ultrasonic treatment of the 2319 Al-Cu alloy during the DED-Arc process is investigated to control the multi-regional microstructure quantitatively. Therefore, the effect of ultrasonic vibration during the DED-Arc process on grain morphology, distribution of precipitates and mechanical properties in different regions are explored in detail. The formation mechanism of differential microstructure is elucidated by using an ultrasonic-heat-flow coupling simulation model for the DED-Arc process. The results indicate that ultrasonic vibration refines the average grain size, leading to 16% and 40% reductions at the molten pool center (MPC) and boundary (MPB), respectively. However, the grains in the semi-melting zone (SMZ) experience coarsening due to the reduced temperature gradient after ultrasonic treatment. The enhanced melt flow rate is considered responsible for both the homogenization of Cu and the fragmentation of the θ-Al2Cu phase. The higher subgrain boundary density in the ITZ leads to an average microhardness of approximately 60 HV, which is lower than that found in the INZ (72.3 HV). Meanwhile, ultrasonic treatment increases the average strength and elongation by 38.1% and 17.5%, respectively, mainly through precipitation strengthening, which results in a strength increment of 91.6 MPa. The slip directions tend to be consistent after ultrasonic vibration, which is conducive to crystal sliding and displays excellent ductility.

Integrated control mechanism of ultrasound and ZrO2 particles on differential microstructures for the wire arc additive manufacturing

ABSTRACT Inhibiting unhomogenised microstructure during the directed energy deposition process with the electric arc energy source (DED-Arc) has become a significant challenge. Ultrasonic vibration leads to the severe stirring of liquid metal and break down dendrites in the inner-layer zone, which promotes the formation of fine grains after rapid solidification. In contrast, the grain refinement effect is not obvious in the semi-melting zone. The addition of ZrO2 particles in the 2319 Al-Cu alloy during the DED-Arc process can drag and pin the grain boundary to prevent grain coarsening in the semi-melting zone. Under the integrated effect of ultrasound and particles, ZrO2 particles can be evenly distributed in different regions, which is beneficial to enhance the microstructure uniformity of the deposition layer and ultimately achieving significant improvement in mechanical properties. The intergrated effect of ultrasonic vibration and particles on strength and elongation reach 13.8% and 92.4%, respectively.

Experimental Study of Arc Erosion in Gas-blasting and Free-burning Conditions in High-voltage Circuit Breakers

Arc erosion behavior depends on varieties of factors, such as the shape and material of contacts, the gas type and the pressure filled in the chamber. In this contribution, experimental research on the gas-blasting and free-burning conditions was carried out in a model circuit breaker to investigate the gas blowing effect on the mass loss of arcing contacts. SF6 was filled in the chamber and copper-tungsten was used as the contact material. Three different peak current amplitudes (5/20/35kA) were selected, and the average mass loss of plug contact was measured after five consecutive arcing tests. The erosion physical process between arc root and contact material is extremely complex. The mass loss was estimated with four different indexes, which include integral of current squared, thermal stress, transferred electric charge and arc energy. It has been found that the arc energy can be used to represent the degree of arc erosion to relate the gas-blasting and free-burning conditions.

Finite Element Modeling of Additive Manufacturing in Case of Metal Parts

Metal Additive Manufacturing has grown from 3D metal printing; this technology leads to manufacturing parts using various metallic materials.Additive Manufacturing technology uses the same principle of slicing a solid model into multiple layers and creating a tool path for each layer, then uploading this data to the printing machine and building the part up layer by layer following the sliced model data using a heat source (laser, electron beam, electric arc, or ultrasonic energy, etc.) and feedstock (metal powder, wire or thin metal sheet, etc.).The Additive Manufacturing process starts with designing the prototype, continues with printer pre-processing, then with printing the prototype, and finally with post-processing to get the final part, followed by testing. This sequence has to be repeated till achieving the desired prototype. This method costs money and time. In this paper, the Simufact Additive Manufacturing software makes a virtual simulation to save time and money. In this virtual modelling, different types of materials can be used. Different approaches can be tested, such as building orientations with various parameters, changing supporting structures, and cutting and support removal to achieve a usable process, which is free from damaging effects on the first time that goes through the build. This paper deals with three types of metal alloys (TiAl6V4, AlSi10Mg, and 316L). Different types of machines, thermal analysis, mechanical calibration, thermal and thermomechanical calibration, were applied to find the set parameters such as laser power, inherent strains, exposure energy fraction, and volumetric expansion factor.

The Benefit of the Process Combination of Wire Arc Additive Manufacturing (WAAM) and Forming—A Numerical and Experimental Study

Wire arc additive manufacturing (WAAM) involves the deposition of weld beads layer by layer using an electric arc energy source. However, during this procedure, the properties of each layer may differ because of unequal thermal distribution, resulting in a difference in microstructure and, therefore, mechanical properties in between the layers. This negative effect can be compensated for by combining WAAM with a subsequent forming process to introduce dynamic recrystallization, which allows a more homogeneous microstructure distribution within the material. This paper investigates numerically and experimentally the hybrid process of combined WAAM and forming of fine-grained mild steel (FGMS) SG3/G4Si (1.5130) to achieve a high degree of recrystallization in all layers of the WAAM-deposited material. Three different possible combinations of WAAM and forming are considered regarding the sequence and setup of the processes to show their influences on the recrystallization behavior. It was found that combining welding and forming allows recrystallization of up to two layers; however, the top layer is not recrystallized. Preliminary simulation results show that this can be resolved by adding a top roller to induce plastic strain after welding, leading to recrystallization in the top layer. The found results promise a certain controllability of the recrystallization behavior.

Strategy of automation of electric arc heating of steel melt in ladle-furnaceStrategy of automation of electric arc heating of steel melt in ladle-furnaceStrategy of automation of electric arc heating of steel melt in ladle-furnace

Prices hike for consumable materials and energy carriers, increase of requirements to steel quality stipulate the items of intensification of ladle treatment processes and decrease of their energy- and material capacity. Analysis of energy losses in ladlefurnace accomplished, as well as basic factors effecting the energy costs during treatment analyzed. A methodology elaborated for making thermal balance of ladle-furnace: it was proposed to present the melt treatment process in ladle-furnace as a series of separate operations, each having specific features of the process (heating, desulphurization, alloying) and their combination. Based on analysis of 20 thousand heats passports at ladle-furnace of MMK BOF shop, a mathematical model of energy supply system of ladle-furnace was elaborated. Based on the analysis made, a strategy of heating automation was proposed. In particular, electric losses were emphasized, t. e. total losses of electric arc energy, in which provisionally losses at arc open part radiation were included. Control of those flows creates conditions for heating efficiency increase. Conclusions were made that decrease of electric losses is observed at prolonged (about 8−12 min) heating periods and sufficient amount of slag, as well as at injection of additives after heating. Such a mode provides decrease of thermal losses by 4−5%. A new technology of steel melt treatment in ladle-furnace was proposed, characterized by decreased consumption of electric energy.

Preparation and arc erosion properties of Ag/Ti2SnC composites under electric arc discharging

New Ag/Ti2SnC (Ag/TSC) composites with uniform microstructure were prepared by powder metallurgy. The superior wettability between Ag and Ti2SnC was confirmed with a contact angle of 14°. Arc erosion properties of Ag/10wt%Ti2SnC (Ag/10TSC) and Ag/20wt%Ti2SnC (Ag/20TSC) contacts were investigated under 400 V/100 A/AC-3 and compared with Ag/CdO contact. The Ag/10TSC contact exhibited comparable arc erosion property to Ag/CdO contact. The fine arc erosion resistance was attributed to the good wettability between Ti2SnC and Ag, the good heat-conducting property of Ag/10TSC, and the slight decomposition of Ti2SnC that absorbed part of electric arc energy. The excessive Ti2SnC significantly decreased the thermal conducting property of the Ag/20TSC composite, resulting in the severe heat accumulation that decomposed Ti2SnC and deteriorated arc erosion property. The oxidation behavior of Ti2SnC under high electric arc temperature was also studied and then an arc erosion mechanism was proposed to get a comprehensive understanding on the arc erosion property of Ag/TSC composites.

Wire arc additive manufacturing of hot work tool steel with CMT process

This study presents investigations on the additive manufacturing of hot work steel with the energy-reduced gas metal arc welding (GMAW) process, which is a cold metal transfer (CMT) process. The paper analyses the influence of arc energy and the thermal field on the resulting mechanical properties and microstructure of the material. The investigations were carried out with hot work tool steel X37CrMoV 5-1, which is used for the manufacturing of plastic moulds, hot extrusion dies, and forging dies. The results show that this steel can be used to generate 3D metal components or structures with high reproducibility, near-net-shaped geometry, absence of cracks, and a deposition rate of up to 3.6 kg/h. The variation of the wire feed speed and the welding speed enables the production of weld beads of width up to 9.4 mm. The mechanical properties of the generated structures can be adapted by the dominant thermal field, which in turn is influenced by the bypass temperature and the electric arc energy. A determining factor to describe the main variables of the welding process is represented by energy per unit length EL. If the bypass temperature is above the martensite start temperature (Ms), there is a homogeneous hardness level along the height of the additively manufactured structure height as long as the energy produced by the welding arc is enough to keep the temperature of all layers above Ms.

Limitation of Electric Arc Energy in LV Switches During Inductive Current Interruption

In this paper, the commutation and switching mechanisms between the operating low-voltage (LV) switch and parallel external branches are presented. Experiments for the limitation of electric arc energy during inductive current interruption were performed for three scenarios: 1) for standalone operated switch (base case), 2) for passive method of arc energy limitation (widely applied RC branch connected in parallel to operated switch), and 3) active method of electric arc energy limitation (current commutation into the external semiconductor branch controlled by the microprocessor system). A typical three-phase electromechanical LV switch with double arc quenching chamber was selected as the tested object. The following parameters were investigated: electric arc resistance, electric arc power, electric arc energy, as well as power and energy generated at the external branch connected in parallel to the operating switch. Measurements were performed for current interruption in a single-phase circuit. In addition, observations of a burning electric arc in the quenching arc chamber were registered by an ultraspeed camera (for two cases: base case and hybrid switching).

Investigation into limitation of electric arc energy in LV switch installed in AC circuit through application of time-controlled contact separation

Summary This paper presents results from performed research on a mitigation of an electric arc in a LV switch through an application of a time-controlled separation of contacts of the tested switch. The research was performed in an AC circuit composed with a voltage source, a pure inductive load, and the tested switch. The aim of performed activities was to determine electric arc energies as well as arcing times in the situation, when the contacts of the operated switch installed in the tested circuit were separated at different instants of the interrupted current. For this purpose, a microcontroller system with a special algorithm implemented was developed. To perform the research, the following angles of the current period were selected to perform the measurements: 35, 90, 145°, and the time just before 0°. To highlight an importance of the supply voltage on a character of the electric arc, its voltage-current characteristics were determined at 2 different voltage levels of the voltage source (12 and 230 V).

3-D MHD Modeling of Internal Fault Arc in a Closed Container

The phenomenon of an internal fault arc in a closed container has been investigated in a magnetohydrodynamic method, which simulates the arcing process ignited between two rod electrodes in air with ac current, including the distributions of temperature and pressure. Particularly, the pressure rises due to the fault arc at different locations within the container are calculated. More significant is that the fraction <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm k}_{\rm p}$</tex></formula> of electric arc energy leading to pressure rise, which is known as thermal transfer coefficient and obtained according to the experimental date before, can be determined by using the simulation method. Compared with the net emission coefficients radiation model, the semiempirical radiation model is more suitable to the pressure calculation with the re-absorption contributing to the pressure rise considered. The influence of different starting temperatures of the reabsorption layer in the semiempirical radiation model on the pressure rise is focused on. It is found that the radiation model with 0.7 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$&lt; \alpha &lt; $</tex></formula> 0.83 is recommended and attempted in the pressure calculation of fault arcs, where <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\alpha$</tex></formula> is an adjusted parameter about the starting temperature of the reabsorption layer. The simulation results of the pressure rise, arc voltage, arc power, and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm k}_{\rm p}$</tex></formula> in the container agree with the experiments.

Research into the energy conversion processes in hybrid plasma devices for applying the coatings

We investigated the processes of transformation of the incoming energy flows into thermal energy of the jet in the arc channel of plasma generator. As the plasma-forming gases, we used the mixtures of air with hydrocarbon gases. It is demonstrated that plasma generators that employ such gas mixtures have two channels for the introduction of energy (the energy of electric arc and the energy of combustion products of combustible gas in the oxidizer) and can be categorized as hybrid devices. The fact of mutual influence of the sources of energy, which is introduced, is proven. Transition to a more complex gas system increases the power of electric arc that burns inside it. Experimentally confirmed is the practical possibility to shift the region of combustion of the components of gas mixture beyond the limits of the arc channel of plasma generator. We established effect of the content of combustible component of the original mixture on the magnitude of energy share that is released outside the plasmatron in the plasma jet. The possibilities to control total capacity of the device and its specific energy characteristics by changing operational parameters of plasma generation are estimated. We established a leading role of the composition of original plasma-forming mixture in this process.

Investigation into Limitation of Arc Erosion in LV Switches Through Application of Hybrid Switching

In this paper, measurement results of the arc erosion limitation in low voltage (LV) switches are presented. The reduction of the arc erosion in the analyzed electromechanical switches was achieved through an application of the hybrid switching in the tested alternative current circuit during interruption of the inductive current. The presented method is based on a commutation of the current during its interruption into a semiconductor branch that is connected in parallel to the operated switch. Thus, this approach is able to limit the electric arc energy efficiently, and as a consequence the arc erosion of the electrical contacts is also significantly reduced. For this reason, the application of the hybrid switching has a positive influence on a lifespan and a reliability of the operated switch. In order to evaluate the influence of the hybrid switching application on an effectiveness of the limitation of the arc erosion in the analyzed LV switches, 50 000 current interruptions were conducted in the tested circuit by each of four analyzed switches. Researches were performed for two standalone switches during a standard current interruption, as well as, for two switches with applied the hybrid switching system. In order to compare the arc erosion of the contact surfaces in both considered cases, scanning electron microscope method coupled with energy dispersion spectroscopy was applied. Moreover, photos of the electric contact surfaces are presented. Additionally, frames registered by high-speed camera during current interruption are presented for both considered approaches.

Auxiliary energy assisted friction stir welding – status review

The present article introduces the auxiliary energy assisted friction stir welding (FSW) processes purported to overcome the shortcomings of the conventional FSW process. The auxiliary energies used for this purpose are thermal energy from electric resistance heat, induction heat, laser, plasma, arc, etc. and mechanical energy in the form of ultrasonic vibration. The state-of-the-art, experimentation and progresses in these FSW variants are surveyed and compiled. The auxiliary energy assisted FSW processes exhibit great promise by having numerous advantages over the conventional FSW in terms improved process window, heat generation, material flow, reduced load on the tools and mechanical properties of joints. Such remarkable advantages would lead these processes to redefine many global technologies and markets in the twenty-first century. However, these variants are still in their preliminary stages of investigation, and more systematic investigations are necessary for their critical assessment. In this aspect, some unsolved issues and challenges are overlooked.

Application of genetic algorithm to improve an electric arc furnace freeboard model based on practical data

Electric arc furnaces are applied to produce steel by melting scrap in a batch process. Despite of the significant role of the off-gas in the electric arc furnace environmental and energy feature, limited research has been carried out specifically on the modelling of the electric arc furnace freeboard. In this research, a reactor base model for electric arc furnace with burner and without burner is extended by considering more inputs to approach real conditions. There are some uncertainties in the measurement or calculation of electric arc furnace inputs due to different constraints. Regarding the multi objective problem and the conflicting nature of objectives, a genetic algorithm is applied to improve the model accuracy. The genetic algorithm found the optimum input parameters in the validated range based on the best compatibility with actual off-gas data. The comparison among different results illustrates the effective performance of genetic algorithm for this problem. This accurate model can be applied in the study of recycling, storage condition and control of the electric arc furnace off-gas for final purpose of energy saving and environmental protection.

Experimental and theoretical study of internal fault arc in a closed container

The characteristics of an internal fault arc in an air closed cylindrical container have been investigated both experimentally and theoretically. Arc voltage, arc current as well as pressure variations at two different locations within the container are measured for electrode gap lengths of 10, 30 and 50 mm with peak current ranging from 1 to 20 kA of direct current (dc). The fraction of electric arc energy leading to pressure rise in the fault arc, which is known as the thermal transfer coefficient (kp), is also obtained according to the experimental data. The arc motion is recorded during the whole arcing by high-speed camera. The radiation intensities of the spectral lines at wavelengths of 510.64 and 515.39 nm of the Cu atom originated from the copper electrodes are detected by spectrometer, from which the arc temperature is obtained by means of the two-line method. A two-dimensional axisymmetric cylindrical coordinate model for fault arc is developed based on magneto-hydrodynamic (MHD) theory with coupled interactions among the flow, temperature, electromagnetic, turbulence and radiation fields taken into account, which simulates the distributions of temperature, pressure, arc voltage as well as kp. Particularly the internal pressure rise and propagation due to fault arc at different locations within the container are analysed. The results show that radiation and turbulence are two key energy transfer mechanisms in modelling the fault arc. Compared with the net emission coefficient radiation model, the P1 model is more suitable to calculate the pressure variation in fault arcs with the re-absorption effect contributing to the pressure rise considered. The computed pressure variation, arc temperature, arc voltage and kp agree with the experimental result within the error range.

The Effect of Electrical Switch Structure to the Contact Voltage-Drop and Temperature Variations

Due to the continuing renovation of the modern technology and the demand for the better consumer products, electricity has become one of the important factors that affect people’s life. The electrical switch is an important element of the electrical device and has been used intensively in industry and transportation devices, such as electrical bicycle, electrical motorcycle, winch etc. As the increasing usage of the electrical switch, the switch quality requirement increases as well. The important factors are contact point mass transferring loss, electric arc energy and contact point resistance and loss. Once the contact point fails to function, the whole electrical device ceases to function. However, regarding the electrical efficiency, in addition to the effect of the contact point materials, the structure is an important factor. In this study the structure of the electrical switch is studied and the effects of spring stiffness, guiding pin and ring to the switch lifespan are discussed. Taguchi method was used to design the experiment. L9(34) Orthogonal Array table was used to perform and discuss the effect of four factors to the desired characteristics; that is to minimize both the contact voltage-drop and the contact temperature increase. Four factors chosen are guiding pin material, compression spring, contact spring and buckle. Test results show that contact spring has the most effectiveness to the contact voltage-drop and temperature increase and is followed by compression spring. Guiding pin and ring type have minimum influence.

Influence of direct reduced iron on the energy balance of the electric arc furnace in steel industry

A model of the EAF energy efficiency was developed based on a closed mass and energy balance of the EAF melting process. This model was applied to industrial EAFs in steel industry charged with scrap or with mixes of scrap and DRI. Complex mass and energy conversion in the EAF was simplified with the introduction of mass and energy conversion efficiencies for the conversion of oxygen and the energy conversion of electrical energy in the electric arcs, chemical energy from the oxidation reactions in the melt and energy from the combustion of burner gas. It turned out that close agreement with observed process parameters from 16 EAFs is obtained by slight variations of the efficiency values. Especially the sensitivity of the steel temperature from the energy conversion efficiency of the electric arc energy indicates the importance of efficient foaming slag operation in EAF steel making. Characteristics and process parameters of DRI charged EAFs are discussed. Model results for a series of case studies illustrate the correlations between DRI chemical composition, DRI portion, oxygen consumption, etc. with electrical energy demand in order to indentify cost-effective EAF process conditions.

CFD Calculation of Pressure Rise Due to Internal AC and DC Arcing in a Closed Container

Computational fluid dynamics calculation results of pressure rise and propagation due to high-current arcs in a closed container are described. The pressure developments at different locations within the container are calculated by changing the current frequency (ac of 50 and 60 Hz, and dc) and the electric arc energy input (up to approximately 1000 kJ). The local pressure oscillation amplitude for AC/50 Hz within the container exceeds that for dc. From the pressure oscillation period and the sound speed distribution in the container, the following conclusions are made. With growing electric arc energy, the pressure amplitude increases because of the resonance effect between the arc power oscillation and pressure waves reflected on the walls. When the electric arc energy reaches a value of around 500 kJ, the pressure amplitude rises significantly. This is considered attributable to superimposition of pressure waves near the container wall caused by low propagation velocity of the pressure waves near the wall. It is necessary to consider this phenomenon for public safety when designing electric power equipment.

High-temperature gasification of carbon-containing raw materials with the use of electric-arc energy and calorific capacity of the gas fuel

Disposal of carbon-containing wastes in a plasma furnace is studied. The influence of the plasma generator power on gasifier efficiency is found for different waste humidities; dependences of specific energy consumption on the waste humidity and air flow rate are obtained. Experimental results are in good agreement with calculations. Sawdust gasification is performed in an electric-arc furnace with an additional heater. The composition of the resultant synthesis gas is analyzed, and the heater performance is determined. It is demonstrated that burning some part of the resultant gas in the heater allows energy consumption to be reduced by 20–25%, as compared with purely plasma gasification.