Weld bead forming rule is very important during double-pulsed gas metal arc welding (DP-GMAW) process, and this process has more advantages than that of conventional arc welding process. This work employed grey rational analysis to explore the weld bead forming rule. Since the latest twinpulse XT DP control process was employed, the parameters adjustment was easier than that of conventional operation. The grey relational analyses between five main process parameters, which were average welding current, welding speed, twin pulse relation, twin pulse frequency together with twin pulse current change in percent, and three key characteristic parameters, which were bead width, bead height and penetration, were conducted to explore the weld bead forming rule. To accurately calculate the grey relational degree, the negative relevancies were transformed to positive ones. According to calculations and corresponding analyses, it can be concluded that the effects of average welding current and welding speed on the weld bead forming and key characteristic parameters of the weld bead were higher than that of other process parameters. Moreover, the relevancies between key characteristic parameters of the weld bead, and process parameters which included twin pulse relation, average welding current and twin pulse current change in percent were positive, while the relevancies between key characteristic parameters and other two process parameters were negative. The work can supply a new method to evaluate the effects of process parameters during the DP-GMAW process on the weld bead forming or other process characteristics, and references for parameters selection and process optimization.

Serious heat accumulation limits the further efficiency and application in additive manufacturing (AM). This study accordingly proposed a double-wire SS316L stainless steel arc AM with a two-direction auxiliary gas process to research the effect of three parameters, such as auxiliary gas nozzle angle, auxiliary gas flow rate and nozzle-to-substrate distance on depositions, then based on the Box–Behnken Design response surface, a regression equation between three parameters and the total score were established to optimized parameters by an evaluation system. The results showed that samples with nozzle angle of 30° had poor morphology but good properties, and increasing gas flow or decreasing distance would enhance the airflow strength and stiffness, then strongly stir the molten pool and resist the interference. Then a diverse combination of auxiliary process parameters had different influences on the morphology and properties, and an interactive effect on the comprehensive score. Ultimately the optimal auxiliary gas process parameters were 17.4°, 25 L/min and 10.44 mm, which not only bettered the morphology, but refined the grains and improved the properties due to the stirring and cooling effect of the auxiliary gas, which provides a feasible way for quality and efficiency improvements in arc additive manufacturing.

Wire and arc additive manufacturing (WAAM) is usually for fabricating components due to its low equipment cost, high material utilization rate and cladding efficiency. However, its applications are limited by the large heat input decided by process parameters. Here, four 50-layer stainless steel parts with double-pulse and single-pulse metal inert gas (MIG) welding modes were deposited, and the effect of different duty ratios and current modes on morphology, microstructure, and performance was analyzed. The results demonstrate that the low frequency of the double-pulse had the effect of stirring the molten pool; therefore, the double-pulse mode parts presented a bigger width and smaller height, finer microstructure and better properties than the single-pulse mode. Furthermore, increasing the duty ratio from 35% to 65% enlarged the heat input, which then decreased the specimen height, increased the width, and decreased the hardness and the tensile strength.

This study focuses on the characteristics of the ripples of the weld bead formed during the double-pulsed gas metal arc welding (DP-GMAW) process. As a special output of the process, ripples include many useful information and can reflect the quality of the welding process. The work analyzed the operational characteristics of the DP-GMAW process based on robot operation which used the latest twinpulse XT DP control process, and then selected five key operational parameters, such as average current, welding speed, twin pulse frequency, twin pulse relation, and twin pulse current change in percent, to explore their effects on the formation and characteristics of ripples. A reliable method of measuring the distance of the ripples was used to provide convincing data. According to a series of experimental observations and analyses, the distance of ripples and appearance under different conditions were obtained. Also, curve fitting equations between each operational parameter and corresponding distances of ripples was obtained. To testify the effectiveness of the curve fitting equations, corresponding verifying experiments were conducted, and the results showed that all the errors were below 10%. In addition, the different levels of the operational parameters on the formation and characteristics of ripples were provided. This work can be a reference for the process and quality control improvement for the DP-GMAW process.

This work is about the influence rule of inclination of welding torch on the formation and characteristics of weld bead during the pulsed-gas metal arc welding (GMAW) process based on the robotic operation. The inclination of welding torch was an important operation condition during the pulsed-GMAW process, because it can affect the formation and quality of weld bead, which was the output of the process. In this work, the different inclination modes and values were employed to conduct actual welding experiments, and some influence rules can be obtained according to examine the surface topography and cross section. Then, to obtain further rules, serious measurements for the geometry characteristic parameters were conducted and corresponding curve fitting equations between inclination angles and the bead width, penetration and bead height were obtained, and the largest error of these curve fitting equations was 0.117 mm, whose corresponding mean squared error (MSE) was 0.0103. Corresponding verification experiments validated the effectiveness of the curve fittings and showed the second order polynomials were proper, and the largest errors between measurements and curve fitting equations for inclination angle under backward mode were larger than those under forward mode, and were 0.10 mm and 0.15 mm, respectively, which corresponded to the penetration and were below 10%, therefore the equations can be used to predict the geometry of the weld bead. This work can benefit the process and operation optimization of the pulsed-GMAW process, both in the academic researches and actual industrial production.

In this paper, a double pulse gas metal arc welding (DP-GMAW) for an AA6061-T6 aluminum alloy based on fewer basic welding parameters than the traditional DP-GMAW is proposed. This study compared the difference in pulse base currents ($\mathsf{\Delta }{I}_{\mathrm{b}}$) and the difference in the pulse peak currents ($\mathsf{\Delta }{I}_{\mathrm{p}}$) by analyzing the electrical signal and morphology properties of welded samples. The results indicated that changing $\mathsf{\Delta }{I}_{\mathrm{p}}$ caused welding defects or even welding failure easily. The welding stability after changing $\mathsf{\Delta }{I}_{\mathrm{b}}$ was much better than that after changing $\mathsf{\Delta }{I}_{\mathrm{p}}$. The individual fish-scale width of the weld joint remained unchanged when $\mathsf{\Delta }{I}_{\mathrm{b}}$ was at different values. In addition, the average absorbed work, tensile strength, yield strength and elongation of the weld joints obtained by different $\mathsf{\Delta }{I}_{\mathrm{b}}$ values reached 31.1%, 60.2%, 52.9% and 37.9% of the base metal, respectively.