Abstract
Ultrasonic energy is introduced into the Metal Inert Gas (MIG) welding arc and weld pool by superposition of an ultrasonic frequency current. In this study, the arc shape, arc energy, and ultrasonic energy that responded to ultrasonic excitation voltage and frequency is investigated. The comprehensive influence of arc and ultrasonic energy on weld formation, microstructure, and mechanical properties is further studied. The arc and ultrasonic energy are analyzed by using a high-speed camera and microphone, respectively. The results showed that the arc width increased, and the arc energy density decreased after the superposition of ultrasonic current. The arc height could be compressed under certain ultrasonic excitation parameters. The ultrasonic excitation voltage and frequency had a direct influence on the ultrasonic energy. The arc height, arc energy density, and ultrasonic energy together determined the weld width. Ultrasound could effectively refine the microstructure of the weld zone and fusion zone but had little effect on the heat-affected zone. Ultrasound improved the hardness of the joint by refining the grain and the second phase. The joint hardness was the highest when the ultrasonic excitation voltage was 100 V, and the frequency was 30 kHz.
Highlights
The ultrasonic energy could effectively compress the arc [1,2], promote droplet transition [3], refine weld microstructure [4,5,6], and improve the mechanical properties of the welded joint [7,8]
The sheet of Ti-6Al-4V was welded by connecting the ultrasonic excitation power supply in parallel with the Tungsten Inert Gas (TIG) welding power supply, and the results showed that the welding arc had broadband response characteristics, the excitation current was the main factor affecting the ultrasonic excitation intensity, and the grain size of the welded joint was refined [10]
The results showed that the arc-ultrasonic energy refined the grain structure in the weld metal and improved the fatigue life of welded joint [17]
Summary
The ultrasonic energy could effectively compress the arc [1,2], promote droplet transition [3], refine weld microstructure [4,5,6], and improve the mechanical properties of the welded joint [7,8]. Zhu used self-made isolation coupling devices to connect the TIG power supply and ultrasonic excitation power supply, and analyzed the influence of ultrasonic excitation current and frequency on the pore and strength of the welded joint of MGH956 alloy. Anna applied the welding power in parallel with the ultrasonic excitation power in the submerged arc welding process to study the influence of the ultrasonic excitation frequency and current on the weld formation, and the research showed that the weld formation had no significant change under the set ultrasonic excitation parameters [19]. Li studied the acoustic-electric characteristics of ultrasonic arc MIG welding of 6061 aluminum alloy and preliminarily analyzed the relationship between ultrasonic excitation energy and ultrasonic. The transverse and longitudinal hardness distribution in the welded joint was measured through a hardness tester
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