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To reduce the consumption of gas metal arc welding shielding gas and improve welding quality, three spiral-diffusion nozzles with different structures were designed in this study. The four evaluation indexes of the flow field quality of shielding gas were determined by analyzing the protective airflow field with the computational fluid dynamics sim...
Citations
... Pires et al. (2010) developed a chamber for measuring CO, NO, and NO 2 concentration in welding. Besides these emissions, the shielding gas (CO 2 or Ar) is usually used for improving the quality of the seam and preventing metal from being oxidized in welding (Pei et al. 2020). However, the shielding gas also poses potential burdens for the environment and it is always ignored. ...
Welding is widely used to make assembly of structural components and it will trigger serious environmental pollution, especially waste gas, i.e., carbon dioxide (CO2), ozone (O3), nitrogen oxide (NOx), and particulate matter (PM). It is hard to accurately measure gas pollutants because of their fluidity and diffusivity. However, the pollutants could be evaluated by exploring its generation procedure, i.e., how these pollutants are produced and how to quantify these pollutants. In this paper, an arc profile–based approach to evaluate the emissions of gas pollutants in welding was proposed. The emission of gas pollutants in welding can be calculated according to the chemical reaction and corresponding reaction condition, i.e., the intensity of discharge that determines the coverage volume of the welding arc. To obtain the coverage volume, the welding arc was observed using a high-speed camera and the arc edge was extracted and reconstructed by a binarization processing based method. A welding experiment was performed for recording the arc shape and measuring the emission of gas pollutants. Results show that the measured concentrations of NOx and O3 are 70% and 79% of the calculated emissions of gas pollutants, respectively. It demonstrates the proposed method is credible and feasible, which can help quantitatively analyze the emission of gas pollutants. Meanwhile, the influence of welding time, welding current, and arc length on the emission of gas pollutants was investigated for lowering emission of gas pollution in welding, in order to support the development of sustainable manufacturing processes.
... It was shown that by using the square-outlet nozzle with boss or circle-outlet nozzle with boss, a sound weld without porosity can be formed. In recent years, Pie et al. designed three spiral-diffusion nozzles with different structures through CFD simulations with the aim of reducing the amount of shield gas used in GMAW in a cross-wind environment and improving welding quality [11]. These nozzles were prototyped by 3D printing with 304 stainless steel and used in welding experiments. ...
The purpose of this study is to develop a novel welding torch with high wind resistance, which can be used for welding outside a building under strong cross-wind. In this paper, a parametric study was carried out using different torch nozzle designs and shield gas flow rates for their optimization. The gas flow around the torch nozzle exit was visualized through the shadowgraph method to evaluate the interaction between the shielding gas flow and the cross-wind. Nitrogen fraction in a weld bead was measured for confirming the shielding effect. Furthermore, CFD simulation was also carried out for obtaining shielding gas flow velocity at the torch nozzle exit. From the result of the above experiments and simulation, effective parameters for improving the shielding effect against the cross-wind were comprehensively discussed. As a result, the nitrogen fraction was found to be decreased by increasing the averaged vertical gas velocity at the torch nozzle exit. For achieving this, it is especially effective to decrease the nozzle diameter or increase the gas flow rate.
Fillet weld is difficult to be processed due to strict requirement on the edge trimming accuracy of the plate. Laser oscillating welding is used to reduce welding defects during laser fillet welding to obtain a welded joint with a better macroscopic morphology. The present work focused on the macroscopic morphology, microstructural observation, joint strength and fracture morphology in dissimilar steel welded joints with laser oscillating welding. Results showed that laser oscillation could significantly reduce the spattering phenomenon during welding, and the shear and tensile strengths of the welded joint with laser oscillation were slightly lower than that of the welded joint without oscillation. This was due to the fact that laser oscillating welding induced more acicular ferrites in the heat-affected zone, slightly reducing the mechanical properties of welded joint. In addition, the fractural morphology of oscillation-treated sample showed a large number of dimples and few tearing ridges, which appeared as intergranular fracture.
In welding, the concept of optimisation had been used, till date, to serve two specific purposes. To obtain any desired weld attributes, a set of required optimal input parameters could be determined utilising the principle of optimisation. To establish an input–output relationship of a welding process accurately, which might be essential to automate it, the tools for optimisation had been used extensively. These optimisation problems were formulated as either a single-objective or multi-objectives or many-objectives ones. Both traditional and nature-inspired optimisation tools were used for the said purposes. This paper provides an extensive review on the role of optimisation in welding. Some research areas have also been identified for future study.
