Figure 2 - available via license: Creative Commons Attribution 4.0 International
Content may be subject to copyright.
Source publication
Aluminum alloy has been widely used due to its excellent workability, and double-pulse metal inert gas welding (MIG) has become a popular technique in aluminum alloy welding. In this study, a cross-complementary test was performed to study the effect of double-pulse characteristics on weld bead formation and mechanical properties in MIG welding. Th...
Contexts in source publication
Context 1
... current and voltage signals in the welding process were collected in real time using a wavelet analyzer (developed by the research group, Guangzhou, China) built on an industrial PC. Figure 2 shows the schematic of the current waveform of the double-pulse MIG welding used in the test, where Ips and tps are the peak current of the strong pulse and its duration, respectively, and Ibs and tbs are the base current of the strong pulse and its duration, respectively. Similarly, Ipw and tpw are the peak current of the weak pulse and its duration, and Ibw and tbw are the base current of the weak pulse and its duration, respectively. ...
Similar publications
AA6061 and AA7075 aluminum alloys were successfully joined by using single-pass and multiple-pass friction stir welding techniques after which the effects on the nugget zone evolution from a second overlapping pass and its welding direction, were investigated. In comparison to single-pass friction stir welding, the application of a second overlappi...
Citations
... This phenomenon indicates that the periodic variation that occurs when both the AC and DC modes are used in MIX-GTAW refines the weld grain size. As Liu et al. [25] reported, the periodic variation of arc force enhances the effect of stirring on the molten pool. The larger the AC ratio is, the denser the fish-scale pattern on the weld surface, as shown in Fig. 4. It can be concluded that the larger the AC ratio is, the stronger the effect of stirring on the molten pool. ...
In this work, AZ31B magnesium alloy is welded using an AC/DC mixed gas tungsten arc welding (MIX-GTAW) process. The effect of the AC ratio on the microstructure and mechanical properties of AZ31B magnesium alloy MIX-TIG welded joints was investigated. The AC ratio range tested was 0 %-100 %. The surfaces of the welds formed at different AC ratios all had fish-scale patterns. The larger the AC ratio is, the denser is the resulting fish-scale pattern on the weld surface. When the AC ratio is 10 %-20 %, the density of the fish-scale pattern is uniform, and the welding seam is more beautiful. Changing the AC ratio parameter does not have an obvious impact on the weld cross-section. With an increase in AC ratio, the average grain size of the fusion zone (FZ) decreases. When the AC ratio exceeds 50 %, the average grain size tends to be stable. The width of the heat-affected zone (HAZ) increases as the AC ratio is increased. The width of the HAZ increase from 250.94 μm at DC (0 %) to 345.90 μm at AC (100 %). It can be found from the X-ray diffraction (XRD) pattern that the second phase particles are β-Mg 17 Al 12. When the AC ratio increase, β-Mg 17 Al 12 content increases, the α-Mg content decreases and the hardness of the FZ decreases. Tensile strength increased first and then decreased with an increase in AC ratio and showed the highest values at an AC ratio of 60 %. The tensile strength decreased from 217.9 MPa to 172.4 MPa as AC ratio increased from 60 % to 100 %.
... The authors concluded that, compared with the traditional single pulse, weak and strong pulses of the double wire alternately stirring the weld pool can produce fish-scale ripples and result in improved mechanical properties. By increasing the low-frequency and base current, Liu et al. [22] enhanced the weld pool oscillation, refined the FZ grain size, and optimized the mechanical properties of the weld. Moinuddin and Sharma [23] investigate the effect of the current difference between leading and trailing currents. ...
... W/PR ratio represents the slenderness of the weld bead. When the W/PR is lower, it is more difficult for the pores to escape the weld pool [22]. ...
Double-wire gas metal arc welding (GMAW) is extensively studied for aluminum (Al) alloy welding due to its high productivity; however, problems such as excessive heat input and porosity remain. In this paper, the low-frequency synchronous (LFS) and low-frequency alternating (LFA) phases based on the double pulse were proposed to improve the heat input of Al alloy double-wire GMAW. Voltage and current waveforms of LFS and LFA phases are acquired, enabling the investigation of heat input characteristics and weld bead formation of LFS and LFA phases. Lastly, the influence of low-frequency phases on weld porosity is assessed. The experimental results have shown that the regular voltage, current waveforms, and continuous weld beads are obtained during LFS and LFA phases. In the LFS phase, the leading and trailing currents simultaneously occur in a strong or weak pulse phase. Further, the heat input fluctuates significantly, causing severe spatter, while fluctuations occur in the weld penetration. Furthermore, weld bead formation quality was poor. Compared with the LFS phase, the leading and trailing currents alternated in a strong or weak pulse phase in the LFA phase. The total LFA phase heat input was smoother, the weld spatter was limited, and the weld width was more uniform. The fish-scale ripples of the LFA phase were more obvious, while the bead formation quality was improved. Additionally, in the LFA phase, the weld pool maintained a fast flow rate and low solidification rate. The geometric parameters of the weld bead were more conducive to the escape of pores. Finally, the LFA phase porosity was notably lower compared with the LFS phase.
... Soltani et al. [16] studied the effect of thermal frequency and current amplitude on the weldability, microstructural evolution and mechanical properties of AA7075 alloy joints welded by DP-GMAW. Liu et al. [17] believed that increasing the base current amplitude or the thermal frequency of the current effectively enhanced the oscillation of the molten pool in the DP-GMAW of an AA6061-T6 aluminum alloy. Yao et al. [18] explored the effect of a low frequency on DP-GMAW weld formation and proposed an empirical formula for the width of fish scales on the welding speed and low frequency. ...
... In this article, the difference in pulse base currents and the difference in the pulse peak currents were set to ∆I b and ∆I p . The definitions of the parameters such as f thermal and f high are shown in the following formulas [17]. ...
... Pulse NBC220 had an Al-Mg-Si alloy welding database with the current range of 50-220 A, and its welding current waveforms included P-GMAW, DP-GMAW and SP-GMAW [27]. After the current and voltage signals were processed by the wavelet analyzer (developed by the research group, Guiyang, China), concise spectrum results and statistical analysis results were obtained by the monitoring and control system (developed by the research group, Guiyang, China), so that the stability of the DP-GMAW process could be evaluated and analyzed [17]. ...
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 (ΔIb) and the difference in the pulse peak currents (ΔIp) by analyzing the electrical signal and morphology properties of welded samples. The results indicated that changing ΔIp caused welding defects or even welding failure easily. The welding stability after changing ΔIb was much better than that after changing ΔIp. The individual fish-scale width of the weld joint remained unchanged when ΔIb was at different values. In addition, the average absorbed work, tensile strength, yield strength and elongation of the weld joints obtained by different ΔIb values reached 31.1%, 60.2%, 52.9% and 37.9% of the base metal, respectively.
The large heat input of submerged arc welding (SAW) usually leads to coarse grains, reducing the mechanical properties of weldments. In this work, double-pulsed (DP) current waveform modulation technology was innovatively applied in SAW. The SAW experiments with/without DP current were performed to investigate the comprehensive effect of low frequency on the welding process stability, weld formation, microstructure and mechanical properties of the Q235 weldments. The results demonstrated that DP current significantly improved welding stability, and high-quality weldments with slight undercuts and spatters, without welding collapse, cracks or hump were obtained by DP-SAW. The low frequency had a significant effect on the spacing between each fish scale pattern. In addition, the microstructure of weld metal mainly consisted of proeutectoid ferrite, acicular ferrite, fine-grained ferrite and slight pearlite, while the microstructure of the heat-affected zone consisted of proeutectoid ferrite and widmanstatten. The stirring action of DP-SAW on the molten pool refined the weld microstructure, which improved the mechanical properties of weldments. With the optimal low frequency of 4 Hz, the microhardness, tensile strength and impact toughness of DP weldment were 188.2 HV, 537.9 MPa and 81.1 J/cm² respectively, which were enhanced by 11.1%, 8.1% and 9.8% compared with that of SP weldment respectively. The obtained results provide a new idea for improving the weld quality of submerged arc welding.
Fullsize Image
Double-pulse gas metal arc welding (DP-GMAW) is a common low-melting-point metal welding method. In this study, a low heat-input double-pulse gas metal arc welding (LHDP-GMAW) was proposed based on DP-GMAW. The welding process stability, weld bead shape, microstructure, and microhardness of 6061 aluminium alloy welding were analyzed for DP-GMAW and LHDP-GMAW with different low-frequency (3, 5 and 7 Hz). Compared with DP-GMAW, the stirring effect of alternating strong and weak pulses on the molten pool of LHDP-GMAW is enhanced and the heat input is reduced. Therefore, the LHDP-GMAW can produce more obvious fish-scale ripples, lower penetration, smaller and more uniform grains, and higher microhardness. This study provides a new solution for improving the welding quality of low-melting-point metal.
