Abstract
Variable polarity cold metal transfer (VPCMT) is a newly developed welding process and has drawn extensive interests because of its potential in further reducing the heat input, offering greater gap bridging ability, and improving the deposition rate. Using 6061 aluminum alloy as an example, this paper systematically investigated the influences of the key parameter in VPCMT, i.e., “positive/negative electrodes ratio (EP/EN Balance),” on weld formation, microstructure, and mechanical properties. It was found that, with the increase of the EP/EN Balance value, the duty cycle of the negative phase was reduced but the peak current and maximum temperature of the weld pool were both increased resulting in a higher heat input. The positive/negative electrode ratio had little impact on the grain misorientation angle in the fusion zone. Hardness of the joint was higher with larger positive duty cycles because of the precipitate phase and small grain size. An increased negative duty cycle resulted in lower heat input leading to insufficient melting of the material and deterioration of the mechanical strength of the welds.
Highlights
In response to the low carbon emission target rectifying the climate change challenge, light weight structures are desired in aerospace, transportation, and many other industrial applications, where welded high strength Al structures are preferred due to its low density, high specific strength, and high structural integrity [1]
This paper is to provide a further study on the influences of the “EP/EN Balance” parameter on welding process in terms of the weld formation, mechanical properties of the joints, and welding defects control
The current increased immediately when the droplet separated from the welding pool, and the current kept nearly unchanged when the droplet increased in size
Summary
In response to the low carbon emission target rectifying the climate change challenge, light weight structures are desired in aerospace, transportation, and many other industrial applications, where welded high strength Al structures are preferred due to its low density, high specific strength, and high structural integrity [1]. Cold metal transfer (CMT) has been widely applied for welding aluminum alloys due to its low heat input and excellent stability in terms of process control. The. A new droplet transfer mode for CMT welding was recently developed by manipulating the ratio of positive/negative polarity, i.e., the so-called variable polarity cold metal transfer (VPCMT) advance (C + A) process [6], which offers greater gap bridging ability, even lower heat input and higher deposition rate. The variable polarity cold metal transfer had lower heat input and better deposition rate ability. The influences of the electrode positive/negative ratio, i.e., “EP/EN balance,” on the welding process and weld quality are still unclear and systematic study is needed for the interest of both industry and academia. Arc length correction (%) 0 want to manipulate the CMT welding process and achieve a better welding quality
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