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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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Journal ArticleDOI
TL;DR: In this paper, an analytical and theoretical study of flat and out-of-position gas metal arc (GMA) C-Mn steel welds containing varying additions of silicon and manganese was conducted.
Abstract: From an analytical and theoretical study of flat and out-of-position gas metal arc (GMA) C-Mn steel welds containing varying additions of silicon and manganese, we conclude that the buoyancy effect (flotation obeying Stokes’ law) does not play a significant role in the separation of oxide inclusions during weld metal deoxidation. Consequently, the separation rate of the particles is controlled solely by the fluid flow pattern in the weld pool. A proposed two-step model for the weld metal deoxidation reactions suggests that inclusions formed in the hot, turbulent-flow region of the weld pool are rapidly brought to the upper surface behind the arc because of the high-velocity flow fields set up within the liquid metal. In contrast, those formed in the cooler, less-turbulent flow regions of the weld pool are to a large extent trapped in the weld metal as finely dispersed particles as a result of inadequate melt stirring. The boundary between “hot” and “cold” parts for possible inclusion removal is not well defined, but depends on the applied welding parameters, flux, and shielding gas composition. As a result of the intricate mechanism of inclusion separation, the final weld metal oxygen content depends on complex interactions among the following three main factors: (1) the operational conditions applied, (2) the total amount of silicon and manganese present, and (3) the resulting manganeseto-silicon ratio. The combined effect of the latter two contributions has been included in a new deoxidation parameter, ([pct Si][pct Mn])−0.25. The small, negative exponent in the deoxidation parameter indicates that control of the weld metal oxygen concentrations through additions of silicon and manganese is limited and that choice of operational conditions in many instances is the primary factor in determining the final degree of deoxidation to be achieved.

38 citations

Journal ArticleDOI
TL;DR: In this article, electron beam welding was used to weld Ti-5Al-2.5Sn alloy sheet with welding current ranging from 14-mA to 20-mA, and the welding current had a significant influence on the weld pool width, micro-hardness and grain size in the fusion zone.

38 citations

01 Jan 1999
TL;DR: In this article, an improved fume chamber was constructed, and fume rates were measured with unprecedented precision for both steady and pulsed-current weld- ing of mild steel using 92% argon/8% CO 2 shielding gas.
Abstract: An improved fume chamber was constructed, and fume rates were measured with unprecedented precision for both steady- and pulsed-current weld- ing of mild steel using 92% argon/8% CO 2 shielding gas. Comprehensive fume maps were constructed depicting fume rates over a wide range of currents and voltages. Fume generation was generally lower under pulsed-current conditions. Theoretical arguments explaining this difference are presented. Accurate fume-generation data and a comprehensive fume formation model are necessary for more sophisticated fume control strategies. This paper in- cludes precise fume generation data for GMAW of mild steel using one shielding gas under steady- and pulsed-current conditions. A physical model introduced by Gray, Hewitt and Dare (Ref. 4) is em- ployed and amplified to explain our ob- servations. Although fume formation has been studied by many scientists, results are dif- ficult to reconcile from one researcher to another. Limited accuracy of some results is one problem, but interpretation and correlation are complicated because of the multitude of variables involved. Many types of welding exist with and without fluxes using a wide range of pos- sible shielding gases. Numerous different electrode and work materials or combi- nations are possible. Much of the prior work has been directed toward the solu- tion of immediate problems in the work- place. Often, fume generation studies in- volve so many variables results are almost impossible to use for theoretical purposes. Our research was designed to produce precise results for narrow con- ditions. Although limited to GMAW of mild steel with a single shielding gas, our fume typography is typical of profiles one should expect with other electrodes and shielding gases. It is hoped that similar re- sults for such systems will become avail- able in the future. Castner (Ref. 3) has provided what may be the most comprehensive study of a single system using the standard AWS fume chamber. Although a comparison of steady- and pulsed-current fume rates

38 citations

Journal ArticleDOI
TL;DR: In this paper, the welding process using 100% CO2 gas was characterized by a large number of spatters, while the penetration depth of a weld was increased and porosity was reduced.

38 citations

Journal ArticleDOI
TL;DR: In this paper, the relationship between weldability and the process parameters of the laser beam-arc distance, welding current and welding speed were investigated using a full factorial experimental design, and the weld quality was evaluated using the weight of the spatter, as porosity formation is a major weld defect in the lap welding of zinc-coated steel sheets.
Abstract: In the lap welding of zinc-coated steel, porosity formation is one of most significant weld defects. It is caused by zinc vapor generated between the steel sheets. Various solutions have been proposed in the past but development of more effective method remains a valuable subject to be investigated. In this study, laser-TIG hybrid welding was applied to the lap welding of zinc-coated steel without a gap. The weld defects could be eliminated by laser-TIG hybrid welding, as the leading TIG arc partially melted the upper sheet, and the coated zinc on the lapped surfaces were vaporized or oxidized before the trailing laser irradiated on the specimen. Optimization of the process parameters for laser-arc hybrid welding process is intrinsically sophisticated because the process has three types of parameters-arc, laser and hybrid welding parameters. In this paper, the relationship between weldability and the process parameters of the laser beam-arc distance, welding current and welding speed were investigated using a full factorial experimental design. Weld quality was evaluated using the weight of the spatter, as porosity formation is a major weld defect in the lap welding of zinc-coated steel sheets. It was found that the weld quality was increased as the laser beam-arc distance and welding current increased, and that this decreased as welding speed increased.

38 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202357
2022103
2021107
2020168
2019206
2018206