Effects of metal vapor on electron temperature in helium gas tungsten arcs
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I. INTRODUCTION
IT is important in welding processes to investigate the effects of metal vapor on the arc plasma. Contamination of the arc plasma by metal vapor can change the thermodynamic properties of the arc. It means that the arc plasma during welding can be quite different from the pure plasma of the shielding gas. Thus, better control of the welding process requires more information about the arc plasma during welding. Many researchers have tried a variety of investigations on metal-contaminated arc plasma. Glickstein[1] presented the result of spectroscopic measurements on a 100A, 2-mm-long argon arc with evaporation from a heated alloy 600 plate. He showed that the arc temperature results determined with a stationary molten anode are similar to the results with a cooled anode. He measured the arc temperature using only the Boltzmann plot method. If there is a slight change of slope, which is derived from the relation between the line intensity and the excitation energy, the results were drastically changed in this method.[2] Etemadi and Pfender[3] presented the result of spectroscopic measurements on a 150 A, 10-mm-long, 800 Torr argon arc with evaporation from the molten copper. They found that the order of temperature decrease was 1000 K at 1 mm above the anode, as compared to the pure argon arc with water-cooled copper anode. Razafinimanana et al.[4] showed the result of spectroscopic measurements on a 90 A, 18-mm-long, atmospheric argon arc with evaporation from the copper anode. They also found that the order of temperature decrease was 2000 K near the anode. Furthermore, they showed the density of neutral copper atoms, derived from the measurement of the line-spectrum intensity. Farmer et al.[5] showed results of spectroscopic measurements on a 200 A, 5-mm-long, atmospheric argon arc with evaporation from a molten SUS304 anode. They reported that the metal vapor had no significant influence on the temperature distribution in the arc. They considered that the strong cathode jet, in the case of the 200 A argon arc, counteracted any tendency for metal vapor to flow or diffuse from the anode to the arc, and changes in plasma transport properties in the arc were not sufficient to change the temperature distributions of the arc. HIDENORI TERASAKI, Postdoctoral Student, MANABU TANAKA, Research Associate, and MASAO USHIO, Professor, are with the Joining and Welding Research Institute (JWRI), Osaka University, 11-1 Minogaoka, Ibaraki, Osaka 567-0047, Japan. Contact e-mail: [email protected] Manuscript submitted August 23, 2001. METALLURGICAL AND MATERIALS TRANSACTIONS A
In computational investigations, Menart and Lin[6] showed results of numerical calculation on a 200 A, 10-mm-long, atmospheric argon arc with copper evaporation. They predicted that the order of temperature decrease is 2000 K near the anode. Gonzalez et al.[7] showed results of numerical calculation on 200 and 300 A, 10-mm-long, atmospheric argon arcs with iron evaporation. Effects of metal vapor on the transport and radiant propert
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