Topic
Shielding gas
About: Shielding gas is a research topic. Over the lifetime, 6697 publications have been published within this topic receiving 58668 citations.
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TL;DR: In this article, the variations of weld porosity and weld shape in aluminum welding with alternate supply method of pure argon and pure helium were compared with conventional gas supply method with pure argON and argon + 67%helium mixture, respectively.
34 citations
TL;DR: In this article, the effect of welding parameters and shielding gas composition in determining the weld shape in Ar-CO2 shielded gas tungsten arc (GTA) welding with SUS304 stainless steel is discussed.
Abstract: The interaction between the variable welding parameters and shielding gas composition in determining the weld shape in Ar-CO2 shielded gas tungsten arc (GTA) welding with SUS304 stainless steel is discussed. The GTA weld shape depends to a large extent on the pattern and strength of the Marangoni convection on the pool surface, which is controlled by the content of surface active element, oxygen, in the weld pool and the welding parameters. Results showed that oxygen absorption into the liquid pool during the welding process is sensitive to the CO2 concentration in the shielding gas. An inward Marangoni convection occurs on the pool surface when the oxygen content is over 100 ppm in the welding pool under Ar-0.3%CO2 shielding. A low oxygen content in weld pool changes the inward Marangoni convection to an outward direction under the Ar-0.1%CO2 shielding. The strength of the Marangoni convection on the liquid pool is a product of the temperature coefficient of the surface tension (dσ/dT) and the temperature gradient (dT/dr) on the pool surface. Different welding parameters will change the temperature distribution and gradient on the pool surface, and therefore, affect the strength of Marangoni convection and the weld shape.
33 citations
TL;DR: In this article, the authors used computational fluid dynamics (CFD) to estimate the local heat transfer between the adjoining shielding gas, laser-induced melt pool and surrounding heat affected zone.
Abstract: Parts fabricated using additive manufacturing (AM) methods, such as laser-powder bed fusion (L-PBF), receive highly localized heat fluxes from a laser within a purged, inert environment during manufacture. These heat fluxes are used for melting metal powder feedstock, while remaining energy is transferred to the solidified part and adjoining gas environment. Using computational fluid dynamics (CFD), the local heat transfer between the adjoining shielding gas, laser-induced melt pool and surrounding heat affected zone is estimated. Simulations are performed for the L-PBF of a single layer of Ti-6Al-4 V. Local temperature, temperature gradients, temperature time-rates-of-change (including cooling rates), as well as dimensionless numbers descriptive of important thermophysics, are provided in order to quantify local convective heat transfer for various laser/gas motion directions. Results demonstrate that L-PBF track heat transfer is highly dependent on relative gas/laser direction which can impact the prior β grain sizes in Ti-6Al-4 V material by up to 10%. It is found that when the laser and gas are moving in the same direction, convection heat transfer is the highest and a ‘leading thermal boundary layer’ exists in front of the laser which is capable of preheating downstream powder for a possible reduction in residual stress formation along the track. Presented results can aid ongoing L-PBF modeling efforts and assist manufacturing design decisions (e.g. scan strategy, laser power, scanning speed, etc.) – especially for cases where homogeneous or controlled material traits are desired.
33 citations
TL;DR: In this article, a novel application of Tungsten/Metal Gas Suspended Arc Welding (T/M-GSAW) was conducted to achieve a bond between copper and stainless steel.
33 citations
TL;DR: The techniques described here, and in particular the use of what is termed u.v.-ozone measurements, will prove useful in further study of ozone generation and CrVI formation and may be applied in the investigation of engineering control of occupational exposure in MIG and other welding process such as Manual Metal Arc and Tungsten Inert Gas.
Abstract: This paper describes the relationships between ultra-violet emission, ozone generation and CrVI production in MIG welding which were measured as a function of shield gas flow rate, welding voltage, electrode stick-out and shield gas composition using an automatic welding rig that permitted MIG welding under reproducible conditions. The experimental results are interpreted in terms of the physico-chemical processes occurring in the micro- and macro-environments of the arc as part of research into process modification to reduce occupational exposure to ozone and CrVI production rates in MIG welding. We believe the techniques described here, and in particular the use of what we have termed u.v.-ozone measurements, will prove useful in further study of ozone generation and CrVI formation and may be applied in the investigation of engineering control of occupational exposure in MIG and other welding process such as Manual Metal Arc (MMA) and Tungsten Inert Gas (TIG).
33 citations