Short-circuiting Transfer Process Research Articles

Stability Analysis of Metal Active-Gas Welding Short-Circuiting Transfer Based on Input Pulsating Energy.

In this study, a platform for a welding experiment, used to collect input and output electrical signals, was constructed, and the algorithm for the input pulsating energy interpolation line (IPEI) was given. Experiments with MAG surface straight line welding were conducted at various voltages. Analysis of the IPEI in relation to the welding current was performed while combining real-world welding occurrences with high-speed camera images of droplet transfer. It was established that the IPEI can be employed as a characteristic parameter to assess the stability of the short-circuiting transfer process in MAG welding. The three criteria for assessing the stability were the spectrum, approximation entropy, and coefficient of variation. A comparative analysis was conducted on each of these approaches. It was determined that the most effective technique is approximation entropy. The approximation entropy of the welding current and IPEI are also highly consistent, with a correlation coefficient as high as 0.9889.

Three-dimensional numerical model of short-circuiting transfer in GMAW

Spatter generation is considered to be a practical problem in the industrial short-circuiting transfer process of gas metal arc welding. Extensive experimental research has been conducted, and some novel approaches have been developed to mitigate splatter generation. In this study, a three-dimensional numerical model of the short-circuiting transfer process was constructed, and the behavior of the liquid bridge was analyzed. The accuracy of the model was verified by comparing the calculation results with the results of an experiment on a water bridge. When short-circuiting transfer was performed with an inclined electrode wire, the liquid bridge was deformed in a manner similar to the deformation of an arch, and it subsequently broke up. Thereafter, the bridge droplet detached as a spatter from the wire tip. This behavior was caused by the difference in the magnetic flux density between the two sides of the liquid bridge. The balance between the surface tension and the electromagnetic force is important for the spatter generation. The inclination angle of the electrode wire, the short-circuiting current, and the surface tension of the molten metal are the most important factors that influence spatter generation.

Dynamic control of current and voltage waveforms and droplet transfer for ultrasonic-wave-assisted underwater wet welding

Ultrasonic vibration can change the dynamic behavior of the bubble and improve the process stability in underwater wet welding (UWW); thus, it has been attempted to profitably control metal transfer process. Arc signals about welding current and arc voltage together with the high-speed imaging detected in conventional UWW and ultrasonic-wave-assisted UWW (U-UWW) were used as information source for determining the droplet transfer mode. The results show that the change in the characteristics of bubble motion affects the droplet transfer process in U-UWW. During the short-circuiting transfer process in small arc voltage, the frequency of arc extinction and the peak of short-circuiting current are both decreased. During the droplet repelled transfer process in middle arc voltage, the droplet repulsive phenomenon is weakened, and the transfer frequency is increased from 7.9 Hz to 10.5 Hz at 34 V. Meanwhile, the droplet diameter is reduced and its transfer stability is improved. During the droplet repelled transfer process in high arc voltage, the frequency and duration time of arc extinction are both reduced. The underlying difference of droplet transfer process between conventional UWW and U-UWW was investigated by the two aspects including ultrasonic wave effect and dynamic bubble effect.

Effects of ultrasonic energy on short-circuiting transfer process in PU-GMA welding

ABSTRACTFor short-circuiting transfer, a smaller short-circuiting current is useful to obtain a better quality of welded joints, such as less spatter and better welding surface. By analyzing images from the high-speed camera, welding electrical signal, and current-voltage (U-I) cycle diagram, stable welding process could be obtained by adding pulsed ultrasonic into the arc. The ultrasonic radiator height, as one of the most important parameters, could affect the energy of acoustics field in pulsed ultrasonic-assisted gas metal arc welding. According to droplet transfer frequency, short-circuiting current and U–I cycle diagram, the ultrasonic radiator height was optimized and the optional ultrasonic radiator height was determined to be 12 mm. The sound radiation force was the main reason for the reducing short-circuit transfer cycle.

Process Stability of Ultrasonic-Wave-Assisted Gas Metal Arc Welding

As a newly developed arc welding method, ultrasonic-wave-assisted arc welding successfully introduced power ultrasound into the arc and weld pool, during which the ultrasonic acts on the top of the arc in the coaxial alignment direction. The advanced process for molten metals can be realized by using an additional ultrasonic field. Compared with the conventional gas metal arc welding (GMAW), the welding arc is compressed, the droplet size is decreased, and the droplet transfer frequency is increased significantly in ultrasonic-wave-assisted GMAW (U-GMAW). However, the stability of the metal transfer has deep influence on the welding quality equally, and the ultrasonic wave effect on the stability of the metal transfer is a phenomenon that is not completely understood. In this article, the stabilities of the short-circuiting transfer process and globular transfer process are studied systematically, and the effect of ultrasonic wave on the metal transfer is analyzed further. The transfer frequency and process stability of the U-GMAW process are much higher than those of the conventional GMAW. Analytical results show that the additional ultrasonic wave is helpful for improving welding stability.

溶接電流・ワイヤ送給制御によるGMA短絡移行プロセスのシミュレーション

In order to realize both of low spattering and low heat input, controlled GMA short-circuiting transfer processes have been developed and practically used in various fabricating sites: Controlled Bridge Transfer (CBT) method by current waveform control, Cold Metal Transfer (CMT) method by wire feeding control, etc. Actually higher performance of GMA welding processes have been provided by deeply understanding mechanism of short-circuiting transfer process. So, we developed three-dimensional numerical model of GMA short-circuiting transfer process including control of welding current and wire feeding speed.It is shown that welding current control method can effectively adjust electromagnetic force for breakup time of liquid bridge in increasing deposition rate and wire feeding control method can effectively improve regularity of short-circuiting transfer process. Both advantages of increase in deposition rate and improvement in regularity of short-circuiting transfer process are provided by hybrid control method combining two control methods.

Novel stability evaluation for short circuiting transfer based on features of input power

An experimental platform of carbon dioxide arc welding, which is used to measure input and output electrical signals, is established. On the basis of input signals, an algorithm for instantaneous input power is introduced. By analysing the waves of instantaneous input power and output current, it is found that the peak of pulsating input power (PPIP) and the pulsating input energy (PIE) are basically consistent with the variation trend of the output current. Short circuiting transfer frequency, coefficient of variation for PPIP and coefficient of variation for PIE are calculated based on the input power characteristics with different wire feedrate. As a result, it shows that all of them can be used to evaluate the stability of short circuiting transfer process. In addition, the optimum method for evaluating the stability is identified, according to comparison of the Pearson correction coefficients, and the results demonstrate that the short circuiting transfer frequency is the best.

Effect of laser on the welding process of short-circuiting transfer MIG welding of aluminum alloys

In this paper, the effect of laser on the welding process in metal inert gas (MIG) welding of aluminum alloys was studied exploiting high-speed imaging and welding electrical signals collecting. Bead-on-plate welding experiments were conducted using conventional short-circuiting transfer MIG welding and laser-short-circuiting transfer MIG hybrid welding. The obtained results point out that it took less time to strike the arc in laser-MIG hybrid welding, and the stability of arc striking was increased. When the laser was introduced into the arc atmosphere, the arc was compressed, and the welding energy was more concentrated. The arc cathode spot was fixed to the laser beam impinging spot, so the arc could burn stably. In laser-MIG hybrid welding, the droplet short-circuiting transfer stability and the weld appearance were improved significantly. Moreover, an analysis method of judging droplet transfer stability which bases on statistical techniques was proposed. By this method, it can be concluded that the short-circuiting transfer process became more stable in laser-MIG hybrid welding.

Effect of Current Waveform on Metal Transfer in Controlled Short Circuiting Gas Metal Arc Welding

With high-speed welding inverter and precisely controlling the welding current with arc-bridge state, advanced pulse current waveforms can be produced to optimize the transfer characteristics of short circuiting transfer welding. In this paper, the images of droplet/wire, and the transient data of welding current and arc voltage were simultaneously recorded to study the influence of peak arcing current, background arcing current and tail-out time on the stability of short circuiting transfer process. It was found that maximum short circuiting transfer stability is reached under specific welding conditions. Any deviation from these conditions will cause abnormal rises in arc voltage indicating instantaneous arc extinguishing and greater spatter. Optimal welding conditions were obtained to achieve the maximum stability of short circuiting metal transfer process.

The CMT short-circuiting metal transfer process and its use in thin aluminium sheets welding

Cold metal transfer (CMT) is a modified metal inert gas welding process based on short-circuiting transfer process, characterised by low heat input and no-spatter welding. The wave control characteristics and its droplet transfer process were analyzed by sensing and image method. The results show that it can realize no-spatter welding and low heat input during welding process. When welding thin sheets, it can obtain small deformation weldment. The low heat input also promotes the gap bridging ability.

Modelling of the short-circuiting transfer process in GMA welding. A numerical model for metal transfer phenomena in GMA welding

During gas metal arc (GMA) welding, such as MAG welding, the welding wire serves as a welding system electrode. The electrode wire is melted by arc heat to form a metal drop on the wire tip. Under the effects of forces such as gravity and electromagnetic force, the metal drop detaches from the wire and transfers to the base metal. Despite welding wire being continuously supplied, molten metal is intermittently transferred to the base metal. For this reason, various factors affecting the progression of GMA welding, such as the arc length and shape alongside the heat source and so-called arc initiation position, fluctuate in time and space. That is to say, metal transfer phenomena control arc stability and are moreover closely related to welding quality itself as well as to operability factors such as generation of spatter and welding defects. To clarify the corresponding mechanisms, it is necessary to undertake theoretical investigations in conjunction with observations by high-speed imaging.

溶滴移行現象のモデル解析（第１報） 短絡移行プロセスのモデル化

In this paper is described a 2D-numerical model of short-circuiting transfer process in GMAW. Time-dependent deformation and/or detachment of the molten drop at the tip of electrode wire were simulated with aids of the numerical solution technique based on finite-difference method, which was developed in order to investigate the effect of electromagnetic force and capillary force on the kinetics of metal transfer process. It is shown that the time required for breakup of liquid metal bridge, formed between the electrode and the weld pool, depends on the drop size before the contact and/or the short-circuiting current value.