Arc Deflection Research Articles

Effect of plasma main arc on droplet transfer in skew-coupling arc welding

Abstract A method of controlling droplet transfer by plasma arc was proposed to solve the problem that cathode spot force hindered the transition of cathode droplet under high current of twin-wire indirect arc (TWIA) in skew-coupling arc (SCA) welding. The effects of the plasma arc on droplet transfer were analyzed from the perspectives of plasma arc current (PAC) and plasma gas flow rate (PGFR). The current-voltage waveform, arc shape and the transition process of droplet were studied by using an electric signal and high-speed camera acquisition system. The results show that controlling droplet transfer by the plasma arc is feasible and effective in the SCA welding. With the increase of the PAC, the degree of the plasma arc deflection increased, and increasing the PGFR has a shrinkage effect on the top of the SCA. Increasing the PAC or the PGFR made the TWIA current vary in a small range, and the plasma arc voltage increase. Increasing the PGFR is more effective to promote the transition of cathode droplet than increasing the PAC, because the plasma fluid force of the TWIA on cathode droplet is enhanced by the double axial thrust of the plasma arc and the TWIA. The cooling effect of the plasma gas on anode droplet weakens the promoting effect of the plasma gas on the transition of anode droplet. The existence of the fluid beam hanging at the cathode wire is important to improve the transition of cathode droplet. The PGFR and the PAC could be cooperatively adjusted to promote the transition process of anode and cathode droplet.

Analysis of Flow Velocity Distribution in Arc Affected by Transverse Magnetic Field with Lateral Gas Flow for Elucidation of Arc Deflection

Analysis of Flow Velocity Distribution in Arc Affected by Transverse Magnetic Field with Lateral Gas Flow for Elucidation of Arc Deflection

Development of a highly productive GMAW hot wire process using a two-dimensional arc deflection

Gas metal arc welding (GMAW) processes are used in a wide range of applications due to their high productivity and flexibility. Nevertheless, the supplied melting wire electrode leads to a coupling of material and heat input. Therefore, an increase of the melting rate correlates with an increase of the heat input by the arc at the same time. A possibility to separate material and heat input is to use an additional wire, which reduces penetration and worsens the wetting behaviour. Consequently, bead irregularities such as bonding defects or insufficient root weldings can occur. In the context of this article, a controlling system for a two-dimensional magnetic arc deflection is presented, which allows to influence arc position as well as material transfer. The analysed GMAW hot wire process is characterised by high melting rates while also realising a sufficient penetration depth and wetting behaviour.

Tomographic measurement of current density and heat input density for tilting TIG arc

ABSTRACT Heat source characteristics in the arc welding process such as temperature distribution of arc plasma, the current and heat input densities to the base metal is very important since they are one of the upstream factors of the process. Many studies have reported the distribution of temperature and metal vapour concentration in welding arc plasma by emission spectroscopy, and the distribution of heat input density to the base metal by split copper anode plate method. These studies generally require the axisymmetric assumption of the arc plasma. However, actual welding arcs are not limited as axisymmetric phenomenon. For example, tilted TIG arc welding is often performed due to the visibility and some reasons, resulting in a non-axisymmetric phenomenon in production sites. In order to measure such target, a tomographic approach is necessary. In this study, multidirectional measurement system with rotary split copper anodes was constructed to measure the non-axisymmetric distribution of the current and heat input densities of tilted TIG arc plasma. Integral values are measured from four directions and converted into a two-dimensional distribution by the image reconstruction method. It was experimentally revealed that as the tilting angle increases, the maximum value of current and heat input density decreases and the low density region of the distribution spreads towards the aiming direction. Although the measurement method using split anode including this study possesses the problem of arc deflection the insulating gap of split part, we found the fitting process on the measured data is useful to reduce this effect.

Influence of arc interactions on heat and mass transfer during a two-arc hybrid welding

The quantitative analysis of the heat and mass transfer in weld pool is of great significance for the optimization of welding parameters in manufacturing process with a high-quality weld bead. In this study, the arc deflections caused by the electromagnetic force of two-arc hybrid welding was calculated. The heat source and arc force models of the hybrid welding were proposed considering the influence of the arc deflection and surface deformation of weld pool. Compared with single heat welding, the distributions of the arc heat energy, arc pressure, and arc shear stress in two-arc hybrid welding were studied based on three-dimensional transient computational models. The temperature field and the fluid flow on the upper surface and the longitudinal and cross -sections of the weld pool were analyzed to reveal the heat and mass transfer in workpiece. Experiments were carried out and the results showed that the simulated cross-section weld bead, thermal cycle, temperature field, and flow field agreed well with the experimental values.

МАГНІТНЕ ПОЛЕ ЗВАРЮВАЛЬНОГО СТРУМУ

The use of one-sided high-speed welding is limited by a decrease in process stability, quality and welded joints toughness. The process stability determines the welds formation, the quality and welded joints toughness. Therefore, increasing process stability, quality and welded joints toughness is an important scientific and technical problem. The welding current magnetic field is created by the arc current and the current flowing through the liquid and base metal. The arc magnetic field creates a pinch-effect and compression under. the action of its own magnetic field, which concentrates energy and increases the electrode, the base metal melting and the welding process efficiency, reduces heat input and increases the welded joints toughness. The magnetic field of the current flowing through the liquid and base metal leads to magnetic blowing, which is the result of arc deflection according to the minimum energy law towards a lower magnetic field, process stability violation, lower quality and welded joints toughness. To regulate and use the welding current magnetic field, a method has been developed for measuring the magnetic field in the joint gap on the upper, lower surface and in the metal thickness middle when current flows through the plates and pipe, the adequacy of which is confirmed in the production conditions of pipe welding for gas and oil pipelines. The developed research technique provides of the welding current magnitude and magnetic field distribution the measurement in the junction gap of the plates and the pipe, which prevents the formation of undercuts and magnetic blowing during one-sided high-speed welding, increases the process stability, the quality and welded joints toughness.

High Efficiency and Quality of Multi-Pass Tandem Gas Metal Arc Welding for Thick Al 5083 Alloy Plates

Multi-pass tandem gas metal arc welding (TGMAW) for Al 5083 alloy plates with 30mm thickness is carried out to study its high efficiency and high quality. The welding process is evaluated by high-speed photographs and electrical signals. The deposition rate and welding time are calculated to characterize the welding efficiency. The bead formation, porosity, microstructure and mechanical properties are tested and analyzed. The results indicate that though arc deflection occurs due to the electromagnetic interference between two arcs during TGMAWprocess, it does not affect the welding process stability significantly. The deposition rate and welding time of TGMAW process are about 15 g/min larger and about 16.7% less than those of gas metal arc welding (GMAW) process respectively, accompanied by the reduction of heat input. The TGMAW welded joint has less porosity and more refined microstructure to contribute to the improvement of mechanical properties (micro-hardness, tensile strength and ductility). It can be concluded that TGMAW process yields excellent performance of welded joint with improved welding efficiency, which makes it extremely practical during welding of thick plates.

GMA zavarivanje korena perlitnih šina korišćenjem skretanja magnetnog luka

GMA zavarivanje korena perlitnih šina korišćenjem skretanja magnetnog luka

GMA zavarivanje korena perlitnih šina korišćenjem skretanja magnetnog luka

GMA zavarivanje korena perlitnih šina korišćenjem skretanja magnetnog luka

Gas Metal Arc Root Welding of Pearlitic Rails Using Magnetic Arc Deflection

Magnetic arc deflection was applied to improve gas metal arc root welds on R260 pearlitic rail steel foot samples. During laboratory welding trials parameter optimization was carried out which comprised the welding current, voltage and speed, layer sequence, filler wire diameter, and the external magnetic field. Results were evaluated by visual inspection, and the lateral and diagonal penetration in cross-sections, as well as the microstructure and the hardness in the HAZ. Additionally, the influence of the external magnetic field on the process was studied using a high-speed camera. Overall best results were finally obtained in high welding current spray arc mode (380-400A) with the 1,6mm solid wire and at high welding speed (65cm/min) and two pass per layer sequence, in combination with maximum 30mT magnetic flux density and increased welding voltage (30-31V) for longer arc. A continuously well-formed root with sufficient lateral penetration was achieved and a smooth transition from base metal to weld metal at the lower edges could be achieved. Inside base metal HAZ the microstructure was fully pearlitic and no soft zone occurred. Furthermore, the size of the HAZ was in comparison to aluminothermic weld reduced by more than 75% in comparison to an AT rail weld.

Observation and analyzation of plasma channel evolution behavior in air flushing electrical arc machining

Blasting erosion arc machining (BEAM) is a novel and promising electrical machining process for difficult-to-cut material processing. In this research, air is applied as an alternative dielectric to investigate the feasibility of dry BEAM. An arc plasma observation experiment is designed and conducted based on a four-channel intensified charge-coupled device (ICCD) high-speed camera in order to observe and investigate the arc plasma expansion and deflection behavior. Furthermore, the influence of the aerodynamic force on plasma column deflection is also studied through comparing the images under different airflow velocities. Voltage and current waveforms were captured to verify the positive effect of air flushing on plasma channels’ deflection behavior. Additionally, crater geometries on the workpiece and electrodes were also observed and discussed as a means to analyze the effect of airflow on machining characteristics. The experimental results reflected that aerodynamic arc disturbing mechanism can be realized in air flushing BEAM, which is a promising process of working fluid for BEAM.

Double arc interference and dynamic behavior characteristics of double wire double-pulsed GMAW

The double wire gas metal arc welding (GMAW) technology combined with double pulse low-frequency modulation offers the benefits of the higher efficiency of double wire GMAW combined with superior weld joint quality offered by double pulse low-frequency modulation. However, the potential for severe double arc interference of double wire double-pulsed GMAW affects the stability of the welding process and has thus far limited its widespread use. In this study, high-speed photography was used to record the arc profiles and arc interference of double wire double-pulsed GMAW in the synchronous and alternant phases, while the voltage and current waveforms were simultaneously recorded. Experimental results demonstrated that the double arc deflection of the strong pulse was more severe than that of the weak pulse due to the high current associated with a strong pulse. It was also discovered that the trailing arc stiffness was lower than the leading arc stiffness. Moreover, the deflection of trailing arc was greater under the influence of the leading arc’s electromagnetic attraction. Whereas, the arc deflection of the pulse stage in the alternant phase was small, less than that of the pulse stage in the synchronous phase, the arc deflection of the background stage was much greater. Furthermore, the arc deflections of the pulse and background stages in the synchronous phase were smaller than the arc deflection of the background stage in the alternant phase. Finally, the leading and in the synchronous phase maintained their stiffness and demonstrated weaker magnetic arc blow, fewer spatters, a more refined fish-scale appearance, and weld beads with better uniformity.

Numerical Simulation of Vacuum Arc Behavior Considering Action of Adjacent Phases in Vacuum Circuit Breakers

In the interrupting process of a three-phase vacuum interrupter, there exists a transverse magnetic field (TMF) in the interelectrode region, which is produced by adjacent phases. The deflection of the vacuum arc caused by TMF will affect the interrupting process of vacuum circuit breakers. In this paper, the vacuum arc characteristics considering the action of TMF produced by adjacent phases is simulated based on a steady 2-D asymmetrical magnetohydrodynamic model. The simulation results show that the vacuum arc will swing around and is especially obvious at the smaller current moments near current-zero during one ac half-cycle, because of the changed direction of TMF produced by adjacent phases. This kind of swing phenomena can also be observed in the electrode erosion of unsuccessful interruption. At the moments near current-zero, axial magnetic field is relatively weaker, while TMF generated by adjacent phases is relatively stronger, therefore, the offset phenomenon of plasma parameters is more significant. Compared with smaller diameter electrode arc, larger diameter electrode has larger arc deflection distance, while its value of plasma parameters is much smaller.

Experimental Study on Deflection Behavior of Vacuum Arcs Under the Influence of External Transverse Magnetic Field

In real power system, when the three-phase short-circuit fault occurs, the vacuum arc in one phase will be influenced by the transverse magnetic field generated by neighbor phases and bus bars. This kind of effect is the main cause of the unstable arc and deflected erosion of contact plates, which leads to the failure of vacuum circuit breakers interruption. The objective of this paper is to get more insight into the influence of external transverse magnetic field (ETMF) on vacuum arc’s behavior. The experiments were conducted in a demountable vacuum chamber with pressure about $10^{-4}$ Pa. The cup-type axial magnetic field contacts were used, whose material was pure copper and the diameter is 35 mm. The uniform ETMF in the arc region was generated by two parallel bulk permanent magnets. The experiments were conducted under different ETMFs (0, 15, and 25 mT) and current levels (1-, 2.5-, and 4-kA rms) with different gap distances (6, 8.5, and 11 mm). The videos of arc column were recorded by a high-speed charge-coupled device camera. Under the action of ETMF, the vacuum arc got deflected. Due to the retrograde motion of cathode spots and Ampere force acting on arc column, the deflection behaviors during three typical periods (that is, initial, peak value, and close-to-current-zero period) were different. Moreover, the deflection level of vacuum arc at current peak value moment was greatly impacted by ETMF and gap distance. Larger the ETMF and gap distance were, higher the deflection level at current peak value moment was. The simulation results of arc deflection based on magnetic-hydrodynamic model were in agreement with experimental results in trends.

Two Heat Source Models to Simulate Welding Processes with Magnetic Deflection

Abstract The technique of weaving by magnetic arc deflection was developed a few years ago to enable the oscillation of the weld pool, thus, causing grain refinement and improving the properties on the welded joint. This paper aims to propose two heat source models that include effects of magnetic arc deflection on a bead-on-plate GTAW process in numerical simulations by using the finite element method. Two cases are studied. In the first case, non-deflected arc and straigth magnectic deflected arc along the torch movement are carried out and compared to numerical simulations. Temperatures at three different points on the backside of the plates (two away from the welding center line and one in its center) and weld pools of SAE 1020 3.2 mm and 6 mm thick steel plates are analyzed. Results obtained by numerical simulations are close to the experimental ones. In the second case, welding with weaving (frequency of 1Hz) on 3 mm thick steel plates is analyzed. The bead width and its visual presentation are compared to experimental results, which show good agreement with both proposed models.

Soldagem TIG com Oscilação Magnética Sincronizada

Resumo: Na busca por melhorias de processos e técnicas de soldagem mecanizada/automatizada, a combinação de modos operacionais, em adição à possibilidade de combinar níveis de corrente de soldagem, tem ganhado espaço. Por meio dessas combinações é possível variar a energia do arco, o que, aliado a movimentos impostos ao próprio arco, pode possibilitar distribuir a energia de forma otimizada para controlar a formação da solda. Uma forma de impor movimento ao arco é por oscilação magnética. Assim, este trabalho explora a sincronização da oscilação magnética com a soldagem TIG. Para tal, foi desenvolvido um sistema para controle simultâneo da oscilação magnética e da fonte de soldagem. Em seguida, foi feita uma caracterização da deflexão (em função da tensão do eletroímã, da corrente de soldagem e do comprimento do arco) baseada em filmagens de alta velocidade e proposto um modelo simples para a deflexão. A oscilação magnética com sincronização foi comparada à sem sincronização, tendo como base de análise o efeito sobre a largura dos cordões de solda. No caso da oscilação sincronizada, foi variado o nível de energia do arco de acordo com sua posição na peça, sendo possível aumentar a largura do cordão no lado da oscilação com maior energia do arco.

Experimental investigation and numerical simulation of triggered vacuum arc behavior under TMF/RMF-AMF contact

A series of triggering experiments was carried out to investigate the characteristics of vacuum arc controlled by TMF/RMF-AMF contacts. During all the experiments, the current ranged from 5–20 kA (rms) and both the arc appearance and behavior of cathode spots were captured by high-speed camera with corresponding arc current and arc voltage. A 3D steady magnetohydrodynamics (MHD) model was built to simulate and analyze the vacuum arc behavior under TMF/RMF-AMF contacts, and arc plasma parameters were calculated based on the above model. The experimental results showed that arc deflection was visible under both low and high current. Under high current, arc core formed, which meant the arc contracted significantly. In addition, the anode became much more active under high current. The behavior of the cathode spots showed that they split themselves into other new cathode spots. Under high current, the bulk of the spots rotated along a clockwise direction on a transverse magnetic field (TMF) plate, which caused much noise and oscillation in the arc voltage. The simulation results show that ions are likely to gather on the branches of the TMF plate on the anode plane, as a result of the effects between the electromagnetic force and pressure gradient of the arc plasma. The current contracts in the center of the TMF plate on the cathode which was due to the thin connecting rod there. The anode contraction of the current is caused by the Hall effect. Ions move along a clockwise direction on the TMF plate, which is driven by Ampere force. The current contraction resulted in significant melting in the center of the cathode surface while the other region suffered from uniform melting. The melting caused by the anode contraction is more significant than that of the cathode.

The influence of arc interactions and a central filler wire on shielding gas flow in tandem GMAW

Tandem gas metal arc welding (GMAW) has been developed in order to increase the productivity of the GMAW process and enables rapid joint completion. However, the very small distance between the two arcs and the superposed magnetic fields causes arc interactions and weld pool instabilities, which reduces the process capability. In this article, an advanced tandem GMA welding process is presented, in which a separation of the two arcs is achieved by a centrally fed filler wire. In high-speed recordings and numerical calculations, the arc stabilizing effect by the filler wire is investigated. The geometric boundary of the filler wire separates the arc streams in the flow area and forms a barrier in the weld pool to reduce unfavorable weld pool oscillation. Furthermore, the arc deflection can be influenced via a hot-wire technique and a positive effect is obtained when the hot-wire polarity is opposed to the arc wires. In addition, the deposition rate can also be increased by the resistive preheating of the filler wire. As a result, the process capability and the productivity of the tandem GMAW process are increased significantly. However, it was shown that even with the more stable advanced tandem GMAW process, sufficient shielding gas coverage can only be achieved within a common shielding gas nozzle used in conventional tandem GMAW processes.

Arc characteristics and metal transfer modes in arcing-wire gas tungsten arc welding

Arcing-wire gas tungsten arc welding is an innovative process developed as a variant of gas tungsten arc welding to reinforce the deposition rate by utilizing bypass arc energy. After establishing an experimental platform, the experiments were conducted to study the arc characteristics, interaction of the main and bypass arcs, and metal transfer behavior. Magnetic arc blow, location of the bypass arc root, and shielding gas flow were found to cause arc deflection and an invisible obstacle between the arcs in arcing-wire gas tungsten arc welding. The bypass arc voltage should be controlled carefully to maintain the stability of the welding process. Globular transfer, short-circuiting transfer, and continuous bridging transfer could be obtained, which were determined by wire feed speed (the melting current) and the distance from the wire tip to the workpiece as well as the welding direction.

Investigation on Welding Arc Interruptions in the Presence of Magnetic Fields: Welding Current Influence

Arc interruptions and, therefore, oscillation in the amount of energy and molten wire delivered to the plate have been observed during tandem pulsed gas metal arc welding (GMAW). It appears that these instabilities are related to the magnetic interaction between the arcs. In order to clarify the possible mechanisms involved, this paper tries to mimic the tandem GMAW arc interruptions. External magnetic fields were dynamically applied to GTAW arcs in constant current mode to verify their resistance to extinction as a function of current level and direction of deflection. High-speed filming was carried out as an additional tool to understand the extinction mechanism. The influence of the welding current level on the arc resistance to extinction was established: The higher the welding current, the more the arc resists to the extinction. The arc deflection direction has minor effect, but arcs deflected backward have more resistance to extinction.