Electric Arc Research Articles

Fabrication and tribological behaviors of copper fiber and carbon fiber reinforced phenol‐formaldehyde resin‐based composite for sliding current collector

AbstractTo achieve new current collector (pantograph strip, electric brush) with easy industrialization and high strength‐toughness, carbon fiber and copper fiber reinforced phenol‐formaldehyde (Cuf/Cf/PF) composite is fabricated by over‐lapping and hot‐pressing processes. Cuf/Cf/PF composite has compact structure and good interfacial bonding between fibers and resin matrix. Cuf/Cf/PF composite is superior to carbon skateboard in terms of electrical conductivity, mechanical strength, and friction behavior. As the carbon fiber content increases, fracture failure mechanism of Cuf/Cf/PF composite transforms from plastic failure into brittle fracture. Wear mechanism is studied by combining electrical contacting and sliding friction, and appropriate arc discharge (2.48%) is benefit for the resin‐based composite to form a smooth tribolayer, but high arc discharge rate (4.83%) rapidly deteriorates wear condition on the worn surface.Highlights Carbon fiber and copper fiber mixing reinforce resin‐based composite. Cuf/Cf/PF composite has high strength‐toughness and low friction. Fracture failure mode changes to brittle fracture with increasing carbon fiber. Wear mechanism includes electrical contacting and sliding friction. Appropriate arc discharge improve friction performance of resin‐based composite.

Recovery of Titanium from Red Mud Using Carbothermic Reduction and High Pressure Leaching of the Slag in an Autoclave

Red mud is a by-product of alumina production, which is largely stored in landfills that can endanger the environment. Red mud, or bauxite residue, is a mixture of inorganic compounds of iron, aluminum, sodium, titanium, calcium and silicon mostly, as well as a large number of rare earth elements in small quantities. Although certain methods of using red mud already exist, none of them have been widely implemented on a large scale. This paper proposes a combination of two methods for the utilization of red mud, first by carbothermic reduction and then, by leaching under high pressure in an autoclave in order to extract useful components from it with a focus on titanium. In the first part of the work, the red mud was reduced with carbon at 1600 °C in an electric arc furnace, with the aim of removing as much iron as possible using magnetic separation. After separation, the slag is leached in an autoclave at different parameters in order to obtain the highest possible yield of titanium, aiming for the formation of titanium oxysulfate and avoiding silica gel formation. A maximal leaching efficiency of titanium of 95% was reached at 150 °C using 5 mol/L sulfuric acid with 9 bar oxygen in 2 h. We found that high-pressure conditions enabled avoiding the formation of silica gel during leaching of the slag using 5 mol/L sulfuric acid, which is a big problem at atmospheric pressure. Previously silica gel formation was prevented using the dry digestion process with 12 mol/L sulfuric acid under atmospheric pressure.

System Identification for Robust Control of an Electrode Positioning System of an Industrial Electric Arc Melting Furnace

Through system identification for robust control methods and utilizing real-time experimental field data, a comprehensive mathematical model is derived that represents the dynamic performance of a single electrode positioning system (EPS) in an industrial electric arc melting furnace (EAF). This EPS is characterized by large, time-varying dynamic parameters, which fluctuate based on operating conditions, specifically as the electrode weight changes within its operational range. The system identification methodology for robust control is developed in four main steps, progressing from experimental design to model validation. This approach yields a nominal model of the actual system and provides a trustworthy estimate of the region of uncertainty of the model, bounded by models of the real system under maximum and minimum electrode weight conditions (limit operating models). The methodology generates three fourth-order time-delay models using an ARMAX structure. The results are promising, as system identification for robust control enables the derivation of mathematical models specifically tailored for designing robust controllers. These controllers significantly enhance the EPS control system’s performance and substantially reduce energy consumption and environmental emissions.

Effect of Electrofriction Treatment on Microstructure, Corrosion Resistance and Wear Resistance of Cladding Coatings

In recent years, the issue of increasing the wear resistance of the working bodies of agricultural machinery designed for cutting and breaking the soil has received special attention. The surface layers of working bodies of agricultural machinery during operation are subjected to intensive abrasive wear, which leads to rapid wear of equipment and a reduction in its service life. The induction cladding method using materials such as Sormait-1 is widely used to increase the wear resistance of tool working surfaces. However, after coating, additional heat treatment is required to improve the physical and mechanical properties of the material and increase its durability. In electrofriction technology (EFT) hardening, the surfaces of the parts are subjected to melting under the influence of electric arcs. In this work, three types of surface treatment of L53 steel have been investigated: induction cladding using Sormait-1, electrofriction treatment, and a combination of induction cladding followed by electrofriction treatment. The microstructure was analyzed using optical microscopy and scanning electron microscopy. Erosion and abrasion tests were carried out in accordance with ASTM G65 and ASTM G76-04 international standards to evaluate the wear resistance of the materials under mechanical stress. A dendritic structure was formed after the induction cladding of the Sormait-1 material, but subsequent electrofriction treatment resulted in a reduction of this dendritic structure, which contributed to an increase in the hardness of the material. However, the highest hardness, reaching 965 HV, was recorded after electrofriction treatment of L53 steel. This is explained by needle martensite in the structure, which is formed as a result of quenching. Further, the influence of structural characteristics and hardness on erosion and abrasion wear resistance was examined. The analysis showed that the material microstructure and hardness have a decisive influence on the improvement of wear resistance, especially under conditions of intensive erosion and abrasive friction.

Development and assessment of a biomass-based energy system for green steel production: A thermodynamic study

ABSTRACT Steel is the fundamental pillar of contemporary society, given its significant greenhouse gas emissions, rapid transformation is required for deep decarbonization of the iron and steel industry. This paper proposes a strategy to generate green steel through the H2-DRI-EAF (Hydrogen direct reduced iron processed in an electric arc furnace) process, leveraging biomass as the primary feedstock. The proposed configuration contains a biomass gasifier to generate hydrogen, which is further used in a shaft furnace to reduce iron ore and is fed to an electric arc furnace to produce Green Steel. India serves as the focal point for this study, with agricultural residue from the four most abundant crops selected as the primary feedstock. With these chosen feedstocks, the system demonstrates the capacity to produce approximately 0.1 kg of hydrogen per kg of biomass. Operating with an overall energy efficiency of 29.2% and exergy efficiency of 41.4%, the plant exhibits a crucial characteristic: the ability to seamlessly integrate different feedstocks without significantly affecting its overall performance. The aim of the current study is to promote bioenergy as a viable pathway for the decarbonization of steelmaking processes.

Optimal Sliding Speed and Contact Pressure Design of On-Load Tap Changer Based on Multivariate Nonlinear Regression

During the voltage regulation of on-load tap changers (OLTCs), the movement of the contacts can easily cause arcing, which may lead to erosion or malfunction. To reduce the energy and probability of arcing, we focus on designing an optimal range for the sliding speed and contact pressure of the contacts to minimize arc energy. Initially, our research introduces a novel OLTC arc testing platform to simulate the motion of static and dynamic contacts, exploring the relationship between different sliding speeds, contact pressures, and factors like arc voltage waveform, arcing rate, arc resistance, and arc energy. Subsequently, by employing multiple nonlinear regression methods, we establish functional relationships between sliding speed and arc energy, as well as contact pressure and arc energy, evaluating the fit using correlation coefficients. Finally, through analyzing their nonlinear behaviors, we determine the ideal sliding speed and contact pressure. The results indicate that when the OLTC contacts slide at an optimal speed between 89 and 103 mm/s and optimal contact pressure between 1.5 and 1.7 N, the arc energy can be minimized, thereby enhancing the performance and lifespan of the on-load tap changer. This study offers feasible insights for the design and operation of OLTCs, aiding in the improvement of power system regulation.

Mutual effects between a gliding arc discharge and a premixed flame

Mutual effects between a gliding arc (GA) discharge at atmospheric pressure and a premixed CH4/air flame were experimentally investigated. Effects of the flame on the GA were studied using simultaneous measurements of the current, the voltage, and the instantaneous images of the plasma columns. The GA in the flame has a thicker and more diffusive plasma column, and it is more frequently ignited at a smaller breakdown voltage than that in the air. The GA extension velocity and the gliding velocity in the flame are larger than those in the air. The electrode voltage drop of the GA discharge in the flame is about 160 V, whereas that in the air is about 220 V. Compared with the GA in the air, the different features of the GA in the flame can be explained by high-temperature, weakly ionized, and species-abundant environment that are generated by the premixed CH4/air flame. Effects of the gliding arc discharge on the premixed flames were demonstrated using planar laser-induced fluorescence of hydroxyl radicals (OH) and formaldehyde (CH2O). OH and CH2O can be formed in the CH4/air mixture in the presence of the GA due to kinetic effects, and the increase of OH and CH2O shows the great potential of the GA for combustion enhancement.

Iron extraction from dust from scrap metal smelting in electric arc furnaces by magnetic separation

Iron extraction from dust from scrap metal smelting in electric arc furnaces by magnetic separation

Study on the Damage Mechanism of an H62-Cu/7075-Al Tribo-Pair Under the Influences of Current Direction and Density

In the present study, we used 7075 Al-H62 Cu and H62 Cu-7075 Al pairs to study the effects of current density and direction on their tribological properties and on the damage caused by the current-carrying friction and wear. We found that, when the current density increased from 0 A/mm2 to 79.61 A/mm2, the coefficients of friction for both pairs decreased. Results obtained after wear indicate that the current direction influences the electromigration between the two tracks, leading to different kinds of damage on the worn surface. In the case of the 7075 Al-H62 Cu pair, damage mainly involved mechanical wear at low current densities. As the current density increased, electro-erosion damage gradually became more dominant. Under the action of a large electric arc, the material surface was severely eroded, and a dense oxide film formed on the material contact surface, ultimately leading to the failure of electrical conduction between the materials. In the case of the H62 Cu-7075 Al pair, damage mainly involved mechanical wear. A layer of copper film was found on the surface of the worn aluminum pin, which caused its mass to be greater than it was before wear.

Fuzzy Logic Controller for Power Control of an Electric Arc Furnace

Electric Arc Furnaces (EAFs) are widely used in the steel manufacturing industry to melt scrap steel by employing a large number of electric arcs. EAFs play an important role in ensuring the efficient production of steel. However, their nonlinear and variable load characteristics have a significant impact on power quality. Because the active power of an electric arc depends on its length, a system for controlling the electrode positions is necessary. This paper presents a control system based on a fuzzy logic controller for the active power control of an electric arc furnace. Individual simulation scenarios were chosen with both reference values and the process taken into consideration. The reference, constant value, step variation, and the sequence of step variation were investigated, as well as step disturbances and the sequence of step disturbances from the viewpoint of the process. Furthermore, the procedure of changing the tap on a transformer was investigated. The proposed solution minimizes the time required for charge elaboration, but the main benefit is that there are no additional costs in the implementation process because the installation remains identical, with the only changes being improvements to soft control management.

What is the embodied CO2 cost of getting building design wrong?

Today, carbon and cost-efficient construction are well matched. However, in the future, as steel production is increasingly done from recycled scrap in electric arc furnaces (EAFs) and concrete mix design is improved, the current balance of CO[Formula: see text] impacts and costs can be altered. When this happens, structural designers need to update their design strategies, and incentives must be put in place to retain the alignment between environmental impact and cost. Here, I assess the potential of carbon taxation to improve the structural design. I also assess the discrepancy in embodied carbon outcomes if construction costs remain constant, but the embodied carbon of materials is varied. Finally, I look at the effect of an early-stage design tool, PANDA, on embodied carbon outcomes of real projects. I find that carbon taxes need to be extremely high to have an effect, and that this effect is limited to certain types of frames. Embodied carbon in construction can become disconnected from costs if the embodied carbon of materials varies heterogeneously. Finally, novel design tools can help designers substantially improve the embodied carbon of their design. This happens despite the absence of a significant monetary incentive to that effect.This article is part of the discussion meeting issue 'Sustainable metals: science and systems'.

INVESTIGATION OF STRUCTURAL FEATURES OF ASPHALTENES USED FOR CARBON MATERIALS SYNTHESIS BY ARC PLASMA TREATMENT

This study presents analysis of asphaltenes isolated from two crude oils: naphthenic-aromatic biodegraded oil and paraffin-naphthenic oil, which have been used as precursors for carbon materials synthesis. The aim of this study is to investigate the interrelationship between the initial structure of asphaltene and the properties of carbon materials. Based on number of spectroscopic and other data, it can be found out that the asphaltenes from napthenic-aromatic biodegraded oil contain less paraffin and more cyclic fragments (aromatic and aliphatic), that are larger and more densely stacked. The asphaltenes of paraffin-naphthenic oil contain a larger number of labile bonds and heteroatoms. Both the asphaltenes contain sulfur enclosed in thiophene and sulfide fragments, nitrogen and oxygen, which are incorporated in different units with different thermal stability. Carbon materials are obtained from both asphaltenes via plasma of an electric arc discharge. The asphaltenes undergo graphitization as a result of plasma treatment, the general trend is an elimination of functional groups and N, S, O. The yields of the carbon materials are almost equal for two studied asphaltenes, giving graphite-like materials as the major product in both cases. The carbon material obtained from the napthenic-aromatic asphaltenes is less thermally stable, the yield of nano-structures and nanofibers are higher compared to the asphaltenes from paraffinic oil, with trace metals remaining during the synthesis process. The carbon material from paraffin-naphthenic oil is amorphous with low heteroatoms content.

Application of Atmospheric Cold Plasma (ACP) for Processing of Raw Bovine Colostrum: Investigation of Antimicrobial Efficacy of Different ACP Treatments

As a rich source of bioactive components, bovine colostrum (BC)1 can be used to produce valuable nutraceuticals. Achieving this goal with common thermal pasteurization processes is challenging due to the heat-sensitive nature of raw BC. This research aimed to investigate the potential of atmospheric cold plasma (ACP) as a novel non-thermal process in inactivating the microbial population in BC. Raw BC was treated with different ACP treatments, including direct dielectric barrier discharge (DBD) in both static and continuous modes, indirect DBD, corona discharge, and gliding arc discharge. The occurrence of creaming and curdling of BC during the treatments was one of the challenges of this research, which was the most and least severe during static and continuous treatments, respectively. The continuous and the indirect DBD treatments were the most and least effective in terms of microbial inactivation. The inactivation of natural microflora with the continuous ACP at the voltage of 15 kV for 20 min was approximately 98%. The indirect DBD treatment led to an increase in the microbial population of BC. In addition, the initial microbial population significantly affected the antimicrobial efficacy of ACP. Treatment voltage and time had a significant effect on the creaming and curdling, natural microflora population, and the total coliform population of the treated samples. The voltage of 14.5 kV and the exposure time of 14.2 min were determined as optimal treatment conditions by response surface methodology (RSM) to achieve the maximum reduction of microbial population, without pH changing of ACP-treated BC. The optimal treatment conditions of ACP reduced the total plate count and total coliform count of raw BC by 1.41 and 3.55 log CFU/ml, respectively, with a minor change in pH. These results promise the potential of ACP technology for BC processing.

Dephosphorization study on hydrogen reduction-melting separation of high-phosphorus oolitic hematite

In order to clarify the dephosphorization mechanism of DRI (Direct Reduced Iron) derived from hydrogen reduced high-phosphorus iron ore during the electric arc furnace melting process, slag was prepared using reagent-grade powder based on the gangue mineral composition of high-phosphorus oolitic hematite. By incorporating varying amounts of CaO, FeOx, and reduced iron powder, experiments simulating the dephosphorization of melting separation slag from DRI with different basicity and metallization rates were conducted at 1873 K. The results show that phosphorus in the iron primarily exists in the form of Fe-P-O spherical slag inclusions and FexP, while in the slag, phosphorus mainly resides within the silicate phases. As the amount of CaO added increases, there is a significant decrease in the phosphorus content within the slag inclusions, and the P-containing compounds in the iron gradually shift from FexP and Fe3(PO4)2 to FeO. As the dephosphorization capacity of the slag increases, the distribution of phosphorus-rich phases in the rapidly cooled slag becomes more extensive. When the basicity increases to 3, the phosphorus-rich phases in the slag transition to 2CaO·SiO2 and 3CaO·SiO2. When the basicity is fixed at 2.5, regulating the metallization rate can control the FeOx content in the melting slag, thereby enhancing the dephosphorization ability of slag. The results show that under conditions of a DRI basicity of 2.5 and a metallization rate of 85%, slag/metal separation can produce low-phosphorus iron with 0.022 wt% P, achieving a dephosphorization rate exceeding 95%.

Decoupling of sulfation reactions to enhance zinc extraction from electric arc furnace dust: Unveiling the significance of O2 activation and mechanistic insights

Electric arc furnace dust (EAFD) is a hazardous solid waste generated during steelmaking, boasting significant concentrations of zinc and iron. Currently, a large amount of EAFD is disposed of in landfills, causing severe environmental pollution and resource wastage. To address this issue, the sulfation roasting followed by water leaching process was proposed, offering efficient zinc extraction, iron separation, low cost, and environmental friendliness advantages. This study presented a novel experimental design that decoupled the sulfation process for EAFD into gas–solid and solid–solid processes to uncover the sulfation mechanisms. During these processes, Zn-bearing phases were successfully converted into zinc sulfate (ZnSO4), while Fe-bearing phases transformed into iron oxide (Fe2O3). The resulting compounds were then separated using a water leaching process, achieving a high zinc extraction rate of 97.21% and a low iron residue of 0.61%, respectively, for the gas–solid sulfation process, and 98.76% and 0.81% for the solid–solid sulfation process. Comprehensive characterizations, in situ diffusion Fourier transform infrared spectroscopy (DRIFTS) experiments, and density functional theory (DFT) calculations provide a deeper understanding of the sulfation restructuring mechanisms in gas–solid and solid–solid roasting processes, highlighting the significant role of O2 activation. In the solid–solid sulfation process, Fe2(SO4)3, derived from the oxidation of FeSO4 by O2, was identified as the predominant compound responsible for sulfation. In the gas–solid sulfation process, sulfite species (SO32-) played a critical role as intermediates, eventually transforming into sulfate species (SO42-) with the assistance of O2. Moreover, adsorbed SO2 underwent oxidation and activation by adsorbed O2, forming the sulfate functional group. Migration of this functional group to the adjacent Zn atom through a transition state, established a Zn-SO4 bond, disrupting the Zn-O bond on ZnFe2O4 and completing the sulfation of ZnFe2O4. This study provides a fresh perspective on the application of sulfation roasting for the extraction of valuable metals, contributing to resource sustainability and effective management of zinc-bearing resources.

Continuous [C] Content Prediction Model in Molten Steel of the All-Scrap Electric Arc Furnace

The continuous [C] content prediction model in molten steel of the all-scrap electric arc furnace was established through the explicit finite difference method combined with numerical simulation based on the thermodynamics and kinetics of the decarburization reaction. Initially, a method to figure out the average [C] content of mixed input scrap was proposed, which provided a basis for subsequent calculations. Furthermore, scrap melting rate, mixing side-blowing / bottom stirring, and oxygen blowing intensity adjustment of oxygen lance had been considered as the three key elements. Decreasing scrap melting time was beneficial to improving the EAF efficiency because it accounts for 80% of the total operation time. The research found that the scrap melting rate was mainly affected by the solid-liquid phase heat transfer and [C] content transfer, and the heat transfer played a dominant role. Applying mixing side blowing / bottom stirring could lead to an improvement in the mass transfer coefficient of the decarburization reaction, and the value was increased from the range of 0.0059 s-1-0.021 s-1 by using single side-blowing to the range of 0.0079 s-1-0.023 s-1. The mass transfer coefficient could be enhanced by the oxygen intensity adjustment of oxygen lances when mixing side blowing / bottom stirring was used. This was a benefit of deeper jet impact zones on the molten steel surface caused by high oxygen flow. After the model was applied to an industrial site, the prediction accuracy of the endpoint [C] content within the error range of ±0.02% and ±0.01% reached 91.2% and 85.7%, respectively.

Investigation of arc spot splitting behavior on aluminum, titanium, and their alloy cathodes under different gas flows

This paper presents an experimental study on the spot splitting behavior of aluminum, titanium, and their alloy cathodes during electric arc discharge. Utilizing high-speed digital cameras, we dynamically captured the splitting motion of cathode arc spots and analyzed their behavior under different pressures of argon, nitrogen, and oxygen. The study also examined the effects of pulsed arc current parameters on spot splitting. We observed a ringlike expansion of pulsed arc spots during splitting, with aluminum cathodes showing better performance than titanium in promoting spot splitting and stabilizing the subsequent motion of the split spots. Oxygen was found to enhance spot splitting more effectively than nitrogen. Furthermore, the parameters of the pulsed arc can control the extent of spot splitting and expansion. These findings provide valuable insights for optimizing arc parameter control in metal film deposition processes.

Evaluation of Material Characteristics and Durability of Mixture of Carbon-Eating Concrete and Electric Arc Furnace Slag via Optimal Carbon Dioxide Curing

This study evaluates the material characteristics and durability of a mixture of carbon-eating concrete (CEC) and electric arc furnace slag. Due to the high C<sub>3</sub>A content present in the electric arc furnace reducing slag binder used in the CEC mix, the initial and final setting times of CEC are observed to be 18.8% and 7.0% faster than those of ordinary Portland cement (OPC), respectively. The optimal carbon dioxide curing condition is determined by varying the pressure and temperature variables within the scope of this study. The 3-day compressive strength of CEC under optimal carbon dioxide curing conditions is observed to exceed the 28-day compressive strength of OPC. The formation of calcium carbonate, which contributes to early strength, is confirmed via scanning electron microscopy and thermogravimetric analysis. Additionally, CEC exhibits significantly higher improvements in abrasion resistivity and chloride-ion penetration resistivity when subjected to carbon dioxide curing compared to OPC.

Identifying patterns in the structural-phase transformations when processing oxide doped waste with the use of carbon reducer

The object of this study is the structural and phase transformations during the carbon reduction of tungsten high-speed steel slag in order to obtain a resource-saving alloying additive. The problem is the loss of precious elements when obtaining and using alloying material from man-made raw materials. Solving the problem is related to the definition of technological parameters to enable the reduction of losses of the corresponding elements. As a result of increasing the degree of scale reduction from 33 % to 72 % and 85 %, the strengthening of the manifestation of the solid solution of carbon and alloying elements in α-Fe relative to FeWO4, FeO and Fe3O4 was revealed. Fe3C, WC, W2C, FeW3C, Fe3W3C, Fe6W6C, VC, V2C, Cr3C2, Cr7C3 and Cr23C6 also appeared. Along with this, rounded and multifaceted particles with different chemical composition and the formation of a spongy microstructure were found. It was established that the most acceptable degree of recovery is 85 %. But achieving a recovery rate of 72 % is also sufficient. This is explained by the fact that the residual carbon in the carbides provides an increased reducing capacity, which is realized during the further reduction of oxides in the liquid metal during alloying. The spongy microstructure results in faster dissolution in contrast to standard ferroalloys, which provides a reduction in melting time while reducing spent resources. No phases with an increased tendency to sublimation were found in the obtained alloying material. That is, no additional conditions are needed that restrain the loss of alloying elements during evaporation with a gaseous phase, which provides an increase in the degree of extraction of the corresponding elements. The properties of the resulting alloying material make it possible to use it in metallurgical production when smelting alloyed steel grades in an electric arc furnace, the composition of which does not have strict restrictions on the carbon content

Validated kinetic modelling of ladle furnace process for predicting inclusions in API steel grade

A kinetic model of ladle furnace (LF) process is developed in C++ format using the FactSage database and ChemApp subroutines. The model considers all the process parameters such as ferroalloy and slag dissolution, wire additions, electrical arcing, steel/slag reactions, reoxidation due to slag eye opening, heat exchange between metal/slag, and refractory dissolution. Further, a correlation for inclusion removal rate was developed as a function of argon flow rate, using discrete phase method (DPM) in Computational Fluid dynamics (CFD). Lollypop samples from steel bath and slag samples were collected from the plant for API steel grade for chemical analysis and inclusion characterisation. At LF_in, the inclusions found were mostly alumina spinel with very low amount of Mg (∼3%), followed by spinel at intermediate stage having ∼15 wt. % of Mg and after Ca treatment, inclusions transformed into CaS and Calcium Aluminate type of inclusions. Overall inclusion weight fraction varied from 136 ppm at LF_in to 93 ppm at LF_out. The model calculations were found to give very good prediction for steel and slag chemistry, and inclusion global composition as compared to the plant results. Predicted temperature was found with an accuracy of ± 5 oC, while the calculated inclusion weight fraction was having an accuracy of ±12 ppm.