Identification of light emitting elements around tungsten electrode during TIG welding using optical emission spectroscopy

et al. 2023

Preprint

Self Cite

A unique mechanism of splashing from a tungsten-based anode was identified during arc discharge. Splashing occurred by breakoff of a liquid metal column, which elongates after a local concavity forms on the molten anode surface. Blue–violet luminescence, emitted by cerium ions originating from additives in the tungsten-based anode, was captured before the concavity formation. The surface temperature exceeded the boiling point of the additives at the time of splashing. The measured droplet speeds suggested that an electromagnetic force contributes the high-speed ejections. Energy dispersive spectrometry mapping also exhibited a remnant of the additives on the longitudinal cross-section of the anode after arc discharge. Based on these experimental facts, the mechanism of anode splashing in arc discharge was deduced as follows: bubble formation of additives at temperatures above their boiling point, bubble bursting at the surface,, micro-plasma jet generation, liquid-column elongation and breakoff under an electromagnetic force, and consequent high-speed droplet ejection.

Section: Resultssupporting

confidence: 61%

“…Spectroscopic analysis identi ed a line-emission spectrum with a wavelength of 456.2 nm originating from cerium ions. This luminescence was caused by the vapour of cerium oxide (an electrode additive), which evaporated and became a plasma 21 . Therefore, the blue-violet luminescent zone in Fig.…”

Section: Resultsmentioning

confidence: 99%

Splashing of tungsten-based anode during arc discharge

Iida

Komen

et al. 2023

Preprint

Self Cite

“…99) In particular, the imaging spectroscopy techniques revealed the temperature and concentration of species in arc plasmas even contaminated with metal vapors. [100][101][102][103][104][105][106][107][108][109] Moreover, oxygen contamination was measured on a water-cooled cupper 110) and investigated by optical visualization techniques of Schlieren method and xenon emission filtering. 4,5) Simulations were also used to obtain numerical information in arc plasmas, which could hardly be measured.…”

Section: Mpbulkmentioning

confidence: 99%

Progress of computational plasma fluid mechanics

2023

Jpn. J. Appl. Phys.

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This article reviews and discusses the recent progresses of studies with the concept of “Computational plasma fluid mechanics”. Computational demonstrations show that the inhouse simulation codes such as PLASTIPC (PLasma All-Speed Turbulence with Implicit Pressure Code) have captured hydrodynamic instabilities and reproduced flow dynamics in thermal plasma – nonionized gas coexisting systems. A unique method has made it feasible to study collective growth of binary alloy nanoparticles by numerical analysis. SPH (Smoothed Particle Hydrodynamics) method with incompressibility modification has achieved complex behaviors of molten metal involving phase change, flow, heat transport, material mixing, and large deformation during arc welding. It is essential to study thermal plasma processes as comprehensive fluid systems in which hot plasma, cold nonionized gas, and materials coexist. The viewpoint and approaches of fluid mechanics as well as plasma physics are indispensable. Computational study will play a more important role in giving us new and deeper insights.

Splashing of tungsten-based anode during arc discharge

Iida

Komen

et al. 2023

Sci Rep

Self Cite

A unique mechanism of splashing from a tungsten-based anode was identified during arc discharge. Splashing occurred by breakoff of a liquid metal column, which elongates after a local concavity formed on the molten anode surface. Blue–violet luminescence, emitted by cerium ions originating from additives in the tungsten-based anode, was captured before the concavity formation. The surface temperature exceeded the boiling point of the additives at the time of splashing. The measured droplet speeds suggested that an electromagnetic force contributes the high-speed ejections. Energy dispersive spectrometry mapping also exhibited a remnant of the additives on the longitudinal cross-section of the anode after arc discharge. Based on these experimental facts, the mechanism of anode splashing in arc discharge was deduced as follows: bubble formation of additives at temperatures above their boiling point, bubble bursting at the surface, micro-plasma jet generation, liquid-column elongation and breakoff under an electromagnetic force, and consequent high-speed droplet ejection.