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, a theoretical approach for the formation of these process deviations and arising material defects is presented, and the impact of these deviations on building surface and part quality is investigated by 3D confocal microscopy, microsections and ultrasonic testing.
Abstract: Selective laser melting is a promising additive manufacturing technology for the production of complex metal components. The technique uses metallic powder as a starting material and a laser for melting and building-up parts layer by layer. One crucial factor influencing the process stability and therefore the part quality is the shielding gas flow. In addition to the shielding properties of the inert atmosphere the gas flow is responsible for the removal of process by-products like spatter and welding fumes originating from the process zone. Insufficient removal or inhomogeneous gas flow distribution may lead to increased interaction between laser and process by-products. Consequences are attenuation of the laser spot as well as redeposition of this by-products on surfaces which are exposed to the laser afterwards. Firstly, a conclusion on all known process by-products is drawn. Secondly, based on these considerations the uniformity of the gas flow is investigated by the width of single welds. Furthermore process deviations are provoked by unfavorable gas flow conditions. Thirdly, the impact of this deviations on building surface and part quality is investigated by 3D confocal microscopy, microsections and ultrasonic testing. Finally, theoretical approach for the formation of these process deviations and arising material defects is presented.
201 citations
TL;DR: In this article, the effects of pulsed gas tungsten arc welding parameters on the morphology of additive layer manufactured Ti6Al4V has been investigated and it was found that the wire feed rate has a considerable effect on the prior beta grain refinement at a given heat input.
Abstract: The effects of pulsed gas tungsten arc welding parameters on the morphology of additive layer manufactured Ti6Al4V has been investigated in this study. The peak/base current ratio and pulse frequency are found to have no significant effect on the refinement of prior beta grain size. However, it is found that the wire feed rate has a considerable effect on the prior beta grain refinement at a given heat input. This is due to the extra wire input being able to supply many heterogeneous nucleation sites and also results in a negative temperature gradient in the front of the liquidus which blocks the columnar growth and changes the columnar growth to equiaixal growth.
197 citations
TL;DR: In this article, the wave control characteristics and its droplet transfer process were analyzed by sensing and image method, and the results show that it can realize no-spatter welding and low heat input during welding process.
197 citations
TL;DR: The cold metal transfer (CMT) is an automated welding process based on dip transfer welding, characterised by controlled material deposition during the short circuit of the wire electrode to the workpiece as mentioned in this paper.
Abstract: Cold metal transfer (CMT) is an automated welding process based on dip transfer welding, characterised by controlled material deposition during the short circuit of the wire electrode to the workpiece. Preliminary results are presented examining the suitability of this process for welding aluminium alloy. Trials show that in comparison with pulsed metal inert gas (MIG) welding, CMT exhibits a higher electrode melting coefficient. By adjusting the short circuit duration penetration can be controlled with only a small change in electrode deposition. Furthermore, by mixing pulsed MIG welding with CMT welding the working envelope of the process is greatly extended allowing thicker material sections to be welded with improved weld bead aesthetics.
192 citations
15 Jan 2009-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a modified metal inert gas welding process based on short-circuiting the transfer process, characterised by low heat input and no-spatter welding, was used to join aluminium to zinc-coated steel.
Abstract: Cold metal transfer (CMT) is a modified metal inert gas welding process based on short-circuiting the transfer process, characterised by low heat input and no-spatter welding. The arc characteristics and its droplet transfer process have been studied by high-speed video photography. The process was used to join aluminium to zinc-coated steel. The results shows that no-spatter welding and low heat input during the welding process can be realized by CMT, and a dissimilar metal joint with good performance can be obtained by the CMT process.
192 citations