Experimental Investigation of Integrated Circular Triple-Wire Pulse GMAW of Q960E High-Strength Steel for Construction Machinery

Abstract

Multi-wire welding has received much attention in the machinery industry due to its high efficiency. The aim of this study was to investigate a novel pulse gas metal arc welding (GMAW) that has circular triple-wire electrodes. The effect of the pulse phage angle on arc stability was particularly studied. Research showed that for typical phase angles the arc stability from low to high is 180°, 0°, and 120°, and the arcs are very stable at 120°. The triple-wire welding was used to weld a 9 mm thick Q960E steel, which is typically used for the arm of construction machinery. When the welding heat input was controlled at 1.26–1.56 kJ/mm, the weld zone was dominated by acicular ferrite, and the coarse-grained zone of the heat-affected zone was a mixed structure of lath martensite and lath bainite. The tensile strength of the welded joint reached 85% of the base metal and the impact toughness was above 62 J, which can meet the requirements of construction machinery. This indicates that the triple-wire welding has great potential to achieve efficient and high-quality welding for the construction machinery.

Prediction of HAZ Microstructure and Hardness for Q960E Joints Welded by Triple-Wire GMAW Based on Thermal and Numerical Simulation

“…Figure 2a presents the welding arc, welding current and arc voltage for a typical triple-wire pulse GMAW process. In the welding process, bright pulsed arcs alternately appeared on the three welding wires, which can effectively minimize the occurrence of arc breaking [31]. The alternation of the pulse arcs was controlled by the main welding machine, which sends trigger signals to the slave welding machines and itself.…”

“…The alternation of the pulse arcs was controlled by the main welding machine, which sends trigger signals to the slave welding machines and itself. This process has been successfully applied to the welding of Q235 steel [29,30] and Q960E steel [31]. A typical weld appearance is shown in the Figure 2b.…”

“…Previously, we have conducted a large number of process study for three-wire welding, especially the effect of welding heat input on the microstructure and properties of the weld joint (See [31]). In order to illustrate the accuracy of this method, we predicted the HAZ microstructures and hardness under different heat input conditions and compared with our previous experimental results.…”

“…When the heat input was 1.56 kJ/mm, it was a mixed microstructure of ML and BL, and the grain size increased significantly. When the heat input increased to 1.89 kJ/mm, the microstructure was mainly composed of BL [31]. 4 summarizes the microstructure and hardness of the HAZ coarse-grained zones obtained by simulation and experiment.…”

“…Recently, we have realized the welding of Q960E high-strength steel, and the influence of heat input on the weld joint has been studied [31]. It was found that the coarse-grained region of heat affected zone (HAZ) is the weakest area of the joint.…”