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.