Effect of dynamic wire in the GTAW process Gonçalves e Silva, Régis Henrique; Correa Riffel, Kauê; Pompermaier Okuyama, Marcelo ...
Journal of materials processing technology,
July 2019, 2019-07-00, 20190701, Letnik:
269
Journal Article
Recenzirano
Odprti dostop
Experimental tests were carried out to evaluate and compare metallic transfer aspects and welding process behavior, in GTAW with dynamic wire feeding in relation to conventional mode (wire insertion ...in a continuous way with constant speed / steady state). Inconel 625 cladded steel plates were laid out at four main welding positions (overhead, vertical up, vertical down and flat). The metallic transfer analysis was based on wire’s tip monitoring, by means of high speed videography and monitoring of the difference of electric potential between tungsten electrode, wire and plate. Continuous wire feeding resulted in rupture of the contact between wire and puddle, which generated large droplets on the wire’s tip, which transferred in irregular intervals. This fact is a common occurrence mainly out of flat position and incurs in irregularity of metal transfer and of oscillographic behavior. For dynamic wire feeding the amount of molten metal in the wire’ tip (droplet) was minimized and the transfer frequency became regular, rendering a more stable and robust process. Also, the risk of electrode contamination was reduced. The benefits of dynamic feeding were observed for both constant and pulsed current.
GMA welding process stability and robustness, as well as weld quality, depend strongly on metal transfer behavior. Evaluating in detail the phenomenon of droplet transfer, considering the detachment ...of metal from the tip of the electrode until it reaches the weld pool and considering the forces acting in the process, is a field of great interest for those looking to control these parameters to achieve the desired characteristics in welding. Currently, there are better high-speed filming systems, which allow the acquisition of better-quality images and open the possibility for the application of computer vision algorithms with the aim of better understanding the dynamics of the metallic transfer. The objective of this research was to develop an algorithm that allows the detection of metal droplets in the footage of the metal transfer process. For this, exploratory work performed an algorithm that managed to detect the drops with high precision. Several methods using findContours, Canny, Laplacian, Sobel, and a weightless neural model were adapted and compared in the detection and measurement of the projected areas, as well as with regard to the processing times. The results generated by the algorithm allowed the detection and monitoring of the metal transferred in the form of drops, as well as the calculation of the projected area and the displacement, allowing for a better understanding of the metal transfer phenomena and, consequently, future conceptions of welding manufacturing control methods.
Arc-based welding processes are susceptible to the magnetic field effects. The electric arc shape, the current density, and the welding energy can influence the weld pool and weld properties, ...providing an additional degree of freedom for process control. This study analyzed the electromagnetic effect in constriction and expansion on arc shape changing and also the consequence on the weld bead geometry. The results demonstrated that with the electromagnetic field action, the electric arc cross-section was changed from cylindrical to elliptical, and that the greater the coils’ excitation, the greater the effect. It was also observed that with the coil excitation current inversion, the ellipse orientation rotates 90° and that the greater the arc constriction (transversally to weld), the greater the penetration and the shorter the bead width. Furthermore, the greater the electric arc expansion (transversally to weld), the lower the penetration and the greater the bead width. The ellipse is rotated electrically without the need for mechanical movement or reassembly, which makes it easy and agile to rotate the ellipse. The coils are electrically powered which allows a continuous range of excitation current (0 to 10 A) and consequently of forces acting on the change in the electric arc shape. With the coil excitation current increase, there is an electric arc area reduction and, therefore, a current density and heat intensity increase. The use of this device allows an additional independent parameter in arc welding processes and allows different weld bead geometries for the same welding current.
Highlights
The electromagnetic constriction and expansion change the cross-section of the electric arc from cylindrical to elliptical, and the inversion of the coil excitation current provides a 90° rotation of this ellipse.
The geometric changes of the arc are reflected in the geometry of the bead, that is, the greater the constriction of the arc, the greater the penetration and the smaller the width of the bead. In the same way, the greater the expansion of the electric arc, the smaller the penetration and the greater the width of the bead.
The reduction in the area of the electric arc is proportional to the increase in the coil excitation current. This reduction in arc area causes an increase in heat intensity and current density.
TIG welding process with dynamic feeding: a characterization approach e Silva, Régis Henrique Gonçalves; dos Santos Paes, Luiz Eduardo; Okuyama, Marcelo Pompermaier ...
International journal of advanced manufacturing technology,
06/2018, Letnik:
96, Številka:
9-12
Journal Article
Recenzirano
Wire forward and backward oscillation in automatic feeding tungsten inert gas (TIG) process have been pointed as a simple technique to achieve high productivity levels and process stability for a ...wider operation range, compared to the conventional version. However, in this case, physical aspects related to the involved phenomena are still not fully understood. Based on that, the present paper addresses a characterization analysis of low frequency dynamic wire feeding process, in order to yield some contribution to the knowledge gain of these phenomena. Both conventional automatic feeding and autogenous process were taken as a reference. The study covers system description as well as metal transfer modes, welding pool temperature gradient, and respective weld geometry. Bead on plate welding was performed and monitored with high-speed and thermographic cameras. Dynamic oscillation showed good stability and proved to be more flexible among other versions, as feeding speed and power do not need to be correlated. In order to enable proper wire dynamic movement monitoring, a special motion measuring system was developed.
Gas protection is very important in arc welding processes and several factors influence its effectiveness. This paper provides a discussion of the applicability of the Schlieren technique to arc ...welding processes. Tests were performed with different types of shielding gas and with GMAW and GTAW torches, in order to highlight differences associated with the various conditions. The results obtained in conjunction with a review of results reported in the literature allowed an evaluation of the limitations associated with the use of the Schlieren technique in the arc welding processes. The most important limitation is that the visualization is inherently difficult when using pure Ar gas, meaning that in most situations it is not possible to adequately visualize the flow interface with atmospheric air, which is the main region of interest in this type of analysis. However, visualization is possible in regions where pure Ar is heated, or when mixtures with other gases are used. In addition, the results obtained with different sources of light were compared and the test was performed by filming the arc welding or with the gas flowing through the torch without the arc. The differences observed in the results obtained are discussed herein.
Recent profusion of advanced GMAW process variants impairs understanding of the nature of each one, with the arc rotation technique among them. This paper’s objective is investigating influences of ...wire-electrode rotation over metal transfer mode and melting rate. A bead on plate experimental matrix was performed and electrical signals acquired in synchronicity with high speed videography. Impacts of electrode rotation were observed on welding voltage and current, whereby rotation speed exerts marked influence. Droplet short-circuiting frequency was affected, culminating in free-flight transfer mode for higher rotation speeds. Increase of melting rate was observed for lower electrical power, indicating efficiency enhancement of the process. Moreover, arc rotation proved to expand controllability of the thermal development of the workpiece. Results are supported by videothermography.
No campo da soldagem, a preocupação com fatores ergonômicos e de usabilidade deve-se à crescente incorporação de tecnologias computacionais e à conseqüente transformação das atividades executadas ...pelos soldadores. Sendo assim, o objetivo deste trabalho foi avaliar a usabilidade de um sistema interativo destinado à soldagem robotizada aplicando-se métodos e técnicas de engenharia de usabilidade. Assim, foram realizados, em laboratório, testes de interação com o equipamento em uma bancada especialmente construída para simular atividades típicas envolvendo a configuração de parâmetros e processos de soldagem. A amostra da pesquisa foi constituída por treze participantes envolvidos em atividades de pesquisa em soldagem. Para a coleta de dados foram utilizados questionários específicos para avaliar a satisfação dos participantes com a usabilidade do sistema. Ainda, para avaliar o desempenho dos participantes durante a realização das tarefas foram registrados os tempos e as taxas de conclusão. Dessa forma, verificou-se que o sistema interativo atendeu ou superou as expectativas dos usuários quanto à utilidade, facilidade de uso, facilidade de aprendizado e qualidade da interface. Por fim, a avaliação de usabilidade forneceu um diagnóstico dos fatores que representaram obstáculos para os usuários, e informações que poderão ser usadas no aprimoramento das próximas versões do equipamento.
No campo da soldagem, a preocupação com fatores ergonômicos e de usabilidade deve-se à crescente incorporação de tecnologias computacionais e à conseqüente transformação das atividades executadas ...pelos soldadores. Sendo assim, o objetivo deste trabalho foi avaliar a usabilidade de um sistema interativo destinado à soldagem robotizada aplicando-se métodos e técnicas de engenharia de usabilidade. Assim, foram realizados, em laboratório, testes de interação com o equipamento em uma bancada especialmente construída para simular atividades típicas envolvendo a configuração de parâmetros e processos de soldagem. A amostra da pesquisa foi constituída por treze participantes envolvidos em atividades de pesquisa em soldagem. Para a coleta de dados foram utilizados questionários específicos para avaliar a satisfação dos participantes com a usabilidade do sistema. Ainda, para avaliar o desempenho dos participantes durante a realização das tarefas foram registrados os tempos e as taxas de conclusão. Dessa forma, verificou-se que o sistema interativo atendeu ou superou as expectativas dos usuários quanto à utilidade, facilidade de uso, facilidade de aprendizado e qualidade da interface. Por fim, a avaliação de usabilidade forneceu um diagnóstico dos fatores que representaram obstáculos para os usuários, e informações que poderão ser usadas no aprimoramento das próximas versões do equipamento.
In the field of welding, the concern with ergonomic and usability factors due to the increasing incorporation of computer technologies and the consequent transformation of the activities performed by welders. Therefore, the objective of this study was to evaluate the usability of an interactive system for the robotic welding by applying methods and techniques of usability engineering. So were performed in the laboratory tests of interaction with the equipment in a specially constructed bench to simulate typical activities involving the configuration parameters and welding processes. The survey sample consisted of thirteen participants involved in welding research. To collect data specific questionnaires were used to assess participants' satisfaction with the usability of the system. Yet, to evaluate the performance of participants during the tasks were recorded times and completion rates. Thus, it was found that the interactive system met or exceeded the expectations of users regarding the usefulness, ease of use, ease of learning and quality of the interface. Finally, the usability evaluation has provided a diagnosis of the factors that represent obstacles for users, and information that may be used in improving future versions of the equipment.
In the field of welding, the concern with ergonomic and usability factors due to the increasing incorporation of computer technologies and the consequent transformation of the activities performed by ...welders. Therefore, the objective of this study was to evaluate the usability of an interactive system for the robotic welding by applying methods and techniques of usability engineering. So were performed in the laboratory tests of interaction with the equipment in a specially constructed bench to simulate typical activities involving the configuration parameters and welding processes. The survey sample consisted of thirteen participants involved in welding research. To collect data specific questionnaires were used to assess participants' satisfaction with the usability of the system. Yet, to evaluate the performance of participants during the tasks were recorded times and completion rates. Thus, it was found that the interactive system met or exceeded the expectations of users regarding the usefulness, ease of use, ease of learning and quality of the interface. Finally, the usability evaluation has provided a diagnosis of the factors that represent obstacles for users, and information that may be used in improving future versions of the equipment.
O processo TIG, em configurações tradicionais, apresenta problemas quando utilizado de maneira autógena com elevadas corrente e velocidade de soldagem. Nessa condição, normalmente ocorrem defeitos no ...cordão, principalmente descontinuidades denominadas humping. Em estudo realizado no LABSOLDA, foram obtidas soldas de excelente qualidade com o processo TIG atingindo velocidades de 1,5 m/min. Este procedimento, utilizando na proteção misturas argônio-hidrogênio, possibilitou velocidade semelhante ao processo MIG/MAG convencional, com a vantagem de ser realizada sem material de adição. O presente trabalho tem o objetivo de fornecer subsídios para uma nova análise da formação dos defeitos na soldagem TIG de elevada produtividade, já que a teoria baseada na pressão do arco não contempla totalmente o que tem sido observado na prática. Foram realizados ensaios com diferentes correntes utilizando argônio, hélio e misturas argônio-hidrogênio no gás de proteção. Os resultados mostram que para a mesma corrente média, à medida que o teor de H2 foi aumentado, ocorreram também gradativos aumentos da área fundida e eficiência de fusão. Foi possível mostrar indícios de que o mecanismo de formação de defeitos não depende somente da pressão do arco, mas sim do balanço entre pressão do arco e quantidade de metal fundido, que é dependente da eficiência de fusão proporcionada pelo gás utilizado.
Under usual configurations, the TIG process presents problems when used autogenously with high current and welding speed. In this condition defects in the weld bead usually occur, especially discontinuities called humping. In a study conducted at LABSOLDA, welds with excellent quality were obtained using the TIG process reaching speeds of 1.5 m/min. Under argon-hydrogen shielding gas mixtures welding speed similar to the conventional MIG/MAG process was allowed, with the advantage of being performed without filler material. The objective of this paper is to provide support for a new analysis of the defects formation in high productivity TIG welding, since the theory based on the arc pressure does not fully contemplate what has been being observed in practice. In this work, tests were performed with different current levels using argon, helium and argon-hydrogen mixtures as shielding gas. The results show that, for the same average current, as the H2 content was increased, there were also gradual increases of melted area and melting efficiency. It was possible to show evidences that the mechanism of defects formation depends not only on the arc pressure, but on the balance between arc pressure and the quantity of molten metal, which depend on the melting efficiency provided by the used gas.
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