Dynamic Behavior Metal Vapor during Gas Tungsten Arc Welding

et al. 2020

Jpn. J. Appl. Phys.

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Cathode erosion is an important issue in the industrial applications of the direct-current arc. However, the mechanism of erosion under molecular gas has not been well clarified. The purpose of this study is to elucidate the erosion mechanism of tungsten-based cathodes in atmospheric pressure Ar-N 2 DC arcs. Tungsten electrodes doped with various metal oxides as electron emitters were investigated. The metal vapor from the cathode was successfully visualized by an optical system that combined a high-speed camera with bandpass filters. The difference in the electrode temperature distribution due to the additives is explained with two factors. The first is the thermal factor that the high melting point additive is difficult to spread on the cathode surface. The second is the chemical factor that the emitter is reduced by nitrogen radicals. Advances in the understanding of such electrode phenomena are expected to lead to expanded applications of nitrogen arcs.

Section: High-speed Visualization Of Metal Vapormentioning

confidence: 99%

Investigation of electrode erosion mechanism in Ar-N₂ DC arc based on visualization of electrode phenomena

Sakura

Yoshida

et al. 2020

Jpn. J. Appl. Phys.

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“…There are past studies that have visualized anode-derived metal vapor in TIG welding. [17,18]. In this experiment, the relative intensity method was used for the observation of tungsten vapor.…”

Section: High-speed Visualization Of Metal Vapormentioning

confidence: 99%

Investigation of erosion mechanism of tungsten-based cathode in Ar–N₂ DC arc

Sakura

Yoshida

J. Phys. D: Appl. Phys.

et al. 2019

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Direct current arc has been used in a wide industrial field. Reducing in cathode erosion is an important issue for process cost reduction, however the erosion mechanism under molecular gas as plasma supporting gas has not been clarified yet. The purpose of this research is to elucidate the erosion mechanism of tungsten based cathodes in atmospheric pressure Ar-N 2 DC arc. The metal vapor generated from the cathode surface was successfully visualized by a high speed camera system with a pair of band pass filters. Combing the visualization with the cahtode temperature measurements provides the tungsten vapor evaporation mechanism; tungsten vapor was generated not from the high temperature part of the cathode tip but from the peripheral part. The arc temperature measurement confirmed that ionization of tungsten atoms in the high-temperature region of the arc caused to this characteristic distribution of tungsten vapor. These findings advance the understanding of such electrode phenomena leading to increased use time of the electrode, and as a result the industrial use of N 2 arcs is expected to expand.

“…In recent, the imaging technique based on high-speed camera observation with imaging monochromators or appropriate band-pass filters has been developed. Temperature distribution of free-burning arc during tungsten-inert gas arc welding process was successfully visualized (Nakanishi et al, 2013;Bachamann et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Investigation of temperature characteristics of multiphase AC arc by high-speed visualization

Imatsuji

Hashizume

et al. 2017

JFST

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The objective of the present study is to understand fluctuation phenomena in a multiphase AC arc as a heat source for material processing based on the high-speed visualization technique of the temperature field. The multiphase AC arc is one of the most attractive thermal plasmas which possess extremely high temperature, high chemical reactivity, rapid quenching capability, and selectivity of the reaction atmosphere in accordance with required chemical reaction. In particular, the multiphase AC arc has a strong advantage on higher energy efficiency compared with other thermal plasmas. Therefore, this heat source has been applied to innovative material processing such as in-flight glass melting. However, the temporal and spatial characteristics of the multiphase AC arc have not been clarified although these are essential to control the characteristics of the products such as particle size distribution, yields of the desired materials. The high-speed visualization of the temperature field of the multiphase AC arc was conducted at 1x10 4 fps as typical framerate to observe the dynamic behavior of the multiphase AC arc in millisecond time scale. An optical system including the band-pass filters was combined with the high-speed camera to observe particular line emissions from atomic argon with negligible emissions from thermal plasma. The obtained experimental results indicated that the temperature of the multiphase AC arc was around 1.0x10 4 K. The arc temperature fluctuated in the range from 0.6x10 4 to 1.3x10 4 K. Consequently, the arc temperature in the multiphase AC arc is sufficiently high to treat the refractory metals and/or ceramics powders. Furthermore, the obtained temperature was well-validated by the conventional spectroscopic method with high accuracy.