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Tsujimura Y.,Osaka University | Nakanishi S.,Osaka University | Kodama S.,Nippon Steel & Sumitomo Metal Corporation | Murphy A.B.,CSRIO Materials Science and Engineering | Tanaka M.,Osaka University
Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society | Year: 2013

In this study, plasma diagnostics in MIG welding of aluminum is performed. In MIG welding, the metal vapor has the large influences on the welding process since the content of the metal vapor in the arc plasma is large. The distribution of metal vapor varies dynamically by a metal transfer. Therefore, the dynamical distributions of temperature and concentration of metal vapor are obtained by the spectral images pictured by high-speed video cameras. Consequently, the metal vapor is distributed near the center axis and the temperature of the arc plasma decreases. Finally, we discuss plasma physics in the welding arc through numerical simulations, using the basic conservation equations of mass, energy, momentum, current and electron density of plasma physics. There is close interaction between the electrode, the arc plasma, the weld pool, and also the metal vapor, which constitute the welding process, and must be considered as a unified system. The simulation results also show the temperature of the arc plasma decreases near the center axis. This is caused by the fact that the energy loss by the radiation increases with increases with the metal content. Source


Nakanishi S.,Osaka University | Tsujimura Y.,Osaka University | Kodama S.,Nippon Steel & Sumitomo Metal Corporation | Murphy A.B.,CSRIO Materials Science and Engineering | Tanaka M.,Osaka University
Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society | Year: 2013

This study shows the time variation of temperature distribution and concentration distribution of metal vapor during gas tungsten arc welding. In this study, stationary gas tungsten arc welding of pure iron was conducted in helium as shielding gas. We investigated the influence of iron vapor on arc plasma and mechanism of iron vapor transportation from the weld pool into the arc plasma. We observed the arc plasma two-dimensionally with spectrometric method. We captured three different monochromatic images simultaneously by three monochromators with high speed video cameras. Thus, two inherence spectra of iron and also one inherence spectrum of helium in arc plasma were obtained. Using these spectra, plasma temperature distribution was obtained. In addition, concentration distribution of iron vapor was obtained by measuring electron density. It was concluded that plasma temperature decreased with increase of iron vapor concentration. Especially, the metal vapor concentration indicated the highest value near the base metal and the temperature around the weld pool decreased rapidly. Source


Kodama S.,Nippon Steel & Sumitomo Metal Corporation | Sugiura K.,Osaka University | Nakanishi S.,Osaka University | Tsujimura Y.,Osaka University | And 2 more authors.
Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society | Year: 2013

In order to clarify the mechanism of metal vapor generation in helium (He) gas tungsten arc plasma, the phenomenon of heat transfer between the plasma and the base metal was examined. In addition to the argon (Ar) arc and He arc, the numerical analyses of imaginary arcs changing the thermal conductivities of respective arcs were conducted, and the plasma temperatures, molten pool temperatures, and the concentrations of metal vapor were compared. As a result, with the increase of the thermal conductivity of the plasma, the maximum temperature of the molten pool surface and the maximum iron (Fe) vapor concentration went up while the plasma temperature in the vicinity of the molten pool dropped. Therefore it is assumed that the phenomenon of Fe vapor generation in the He arc and the phenomenon of the plasma temperature drop near the molten pool are influenced greatly by the high thermal conductivity of the He plasma. Source


Sugiura K.,Osaka University | Kodama S.,Nippon Steel & Sumitomo Metal Corporation | Tsujimura Y.,Osaka University | Murphy A.B.,CSRIO Materials Science and Engineering | Tanaka M.,Osaka University
Yosetsu Gakkai Ronbunshu/Quarterly Journal of the Japan Welding Society | Year: 2013

It is problem that nitrogen absorption in gas tungsten arc (GTA) weld metal. Recently, various arc welding simulation techniques have been developed. However, there are few models dealing with the absorption and a mixture of a shielding gas, an atmosphere and a metal vapor.. In this study, intruding behaviors of the atmospheric gas (N2) into the molten poor and nitrogen transportation phenomenon in the molten poor during GTA welding was investigated using a unified numerical model. This model includes the tungsten cathode, arc plasma and base metal. We take atmosphere (N2), shielding gas from the gas nozzle and metal vapor from the molten poor into consideration. As a result, we show nitrogen concentration distribution and nitrogen transportation in the molten poor. Additionally, we clarify that these behaviors are affected by the arc plasma characteristics. Source


Hess M.,Odjel Znanosti I Tehnologije Polimera | Allegra G.,Odjel za kemiju | He J.,Kemijski Institute | Horie K.,Kozukayama | And 7 more authors.
Kemija u industriji/Journal of Chemists and Chemical Engineers | Year: 2015

The document gives definitions of terms met in the conventional thermal and thermomechanical characterisation of polymeric materials. © 2015, Croatian Society of Chemical Engineers. All rights reserved. Source

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