Double Pulse Low-Frequency Modulation for High-Power Double-Wire Pulsed GMAW

Abstract

A double pulse low-frequency modulation method was proposed to improve heat input control and enhance weld quality during high-power double-wire pulsed gas metal arc welding (GMAW). By constructing a mathematical model, relationships between parameters of double pulse low-frequency modulation and energy input were analyzed. A correction coefficient was added to overcome physical characteristics of charging and discharging in a welding circuit. Thus, qualitative relationships between parameters of double pulse low-frequency modulation and energy input were described more accurately. Bead-on-plate welding experiments were conducted in a synchronous phase mode. A stable welding process was achieved and perfect weld bead shapes were acquired. Modulation frequency imposed a significant effect on both weld width and penetration, while modulation duty cycle had a significant effect on penetration and little effect on weld width. Modulation frequency significantly influenced refinement of grain size. Weak and strong pulses of low-frequency modulation improved heat input control, strengthened stirring action of double pulse on weld pool, and enhanced fluidity of molten metals, thereby contributing to optimization of weld quality.

Review of the Recent Trends of Process Monitoring and Control for Double- Wire GMAW Process

“…In addition, it can be seen that the work [49] has some similar points to the work [39], both of the two works introduced high-frequency modulation to the original current waveform. Actually, the trailing current in the Figure.…”

“…To improve the heat delivery and quality of weld bead, Wu et al [39] proposed to add a double pulses low-frequency modulation for a high-power double-wire GMAW process. The double pulses included a consecutive weak and strong pulse, as shown in Figure .4.…”

“…5 (b) can also be considered as a form of double pulse. However, the work [39] had more complex structure than that of the work [49]. We suggested that to achieve control actions with high performance, low complexity was also an important element, however, to deal with the system with different actual operational environment and condition, more appropriate system design and configuration should also be seriously considered during the applications.…”

Effect of low heat-input double-pulse gas metal arc welding on weld formation and microstructure of 6061 aluminium alloy

“…Wu et al [18] introduced a dual-wire DP-GMAW with a median current waveform based on the conventional rectangular pulse and found that changed the median current, the average welding current also changed. The research on increasing the stirring effect of the molten pool mainly includes low-frequency [19, 20], current amplitude [21], and additional technology [22]. Liu et al [23] observed the change of the molten pool profile during the DP-GMAW welding process and found that the molten pool profile changes periodically with the change of low-frequency.…”

Morphological and Microstructural Evaluation of Welding Beads Manufactured by SAW Process with Thermal Pulsing

“…The overlap between these points depends on the pulse frequency and the welding speed [1]. Based on the information available in the literature, there are numerous advantages attributed to this technique, including greater control over the molten pool [2,3], reducing the heat input [4], residual stresses and distortions [4,5] and grain refinement in the molten zone [2][3][4]6].…”