Shielding gas

About: Shielding gas is a research topic. Over the lifetime, 6697 publications have been published within this topic receiving 58668 citations.

Pipe welding apparatus

Abstract: In pipe welding apparatus (1) for welding pipe sections together to form a pipeline,upper and lower pipe sections (2, 3) are abutted, end-to-end, and welded together by two or more welding heads (5) that travel around a circumferential guide (4) extending around one of the pipe sections (2). Welding supplies, such as electric power, cooling water and shielding gas are supplied from supply equipment (9, 10, 11) through a distribution manifold (18). The supply equipment (9, 10, 11) thus distributes welding supplies to each of the welding heads.

Investigation of the relationship between arc-anode attachment mode and anode temperature for nickel nanoparticle production by a DC arc discharge

Abstract: Multiple and constricted arc-anode attachment modes were observed in helium arc discharge to prepare nickel nanoparticles. The electron overheating instability resulted in the formation of multiple attachment modes. The effects of hydrogen concentration and shield gas flow rate on the characteristics of nickel nanoparticles were investigated. The evaporation rate of anode material contributed to forming different arc-anode attachments. The surface temperature of the electrode was measured during the arc discharge by two-color pyrometry combined with a high-speed camera which employs appropriate band-pass filters. The relationship between the arc-anode attachment mode and the temperature behavior of the anode surface was investigated by using two synchronized high-speed cameras. The waveform of anode jet area variation with time follows that of the highest temperature variation of anode surface with time. The fluctuation of the highest anode temperature increased when the arc anode attachment changed from multiple into constricted mode. The highest temperature fluctuation and stability of the arc contributed to nanoparticle size distribution. Nickel nanoparticles with large productivity and narrow size distribution were obtained when shield gas was employed by controlling the residence time of nanoparticle growth. The formation mechanism of different arc-anode attachment modes was explained.

Dissimilar welding of super-duplex and super-austenitic stainless steels

Abstract: Dissimilar welding of super-duplex stainless steel 2507 (UNS S32750) to super-austenitic stainless steel 6Mo (UNS S31254) was studied using nickel-alloy filler materials ERNiCrMo-13 and ERNiCrMo-3 as well as super-duplex filler material ER2594 in GTAW. It was shown that mechanical properties of the dissimilar welded joints made with nickel-alloy filler materials and super-duplex stainless steel filler meet the requirements in the related international standards. Intermetallic phases were found in the 2507 fusion line and the weld metals with nickel-alloy filler materials while intermetallic phases were observed in the 6Mo fusion line with super-duplex filler. Intermetallic phases were observed in the weld metals with super-duplex filler and shielding gas of pure Ar, but not with the same filler and shielding gas of Ar + 2%N2. The dissimilar welded joints have passed the ASTM G48A test at 45 °C made with nickel-alloy filler materials ERNiCrMo-13 and ERNiCrMo-3, at 40 °C with super-duplex filler and shielding gas of Ar + 2%N2, and at 35 °C with super-duplex filler and shielding gas of pure Ar. Based on the mechanical properties and pitting corrosion resistance of the dissimilar welded joints of 2507 to 6Mo, the filler material can be ERNiCrMo-13 as the first choice, ERNiCrMo-3 as the second choice and super-duplex filler ER2594 together with shielding gas of Ar + 2%N2 as the third.

Dynamic analysis of droplet transfer in gas–metal arc welding: modelling and experiments

Abstract: In this work, a pulsed welding process is investigated to highlight how a time-varying profile of current impacts the metal transfer dynamics. First, the process is recorded using a high-speed camera, allowing us to qualitatively evaluate the effectiveness of metal transfer and the synchronization of droplet detachment with current peaks. Second, a time-dependent axisymmetric 2D model is developed to take into account both the droplet detachment using a volume-of-fluid model and the production and diffusion of metal vapour through a simplified diffusion model (neglecting demixing effects). We report a comparison between experimental and simulative results of a pulsed transfer mode for a steel wire (φ = 1 mm) and Ar shielding gas.