Coupled mechanisms of the keyhole, energy transfer and compositional change associated with the variable polarity plasma arc process

2020 ◽  
Author(s):  
Dongsheng Wu ◽  
Shinichi Tashiro ◽  
Xueming Hua ◽  
Manabu Tanaka
Keyword(s):  
Energy Transfer ◽  
Plasma Arc ◽  
Compositional Change ◽  
Variable Polarity ◽  
Variable Polarity Plasma Arc

scholarly journals Evolution of Microstructure and Mechanical Properties in a Single-Stage Aged 7075 Aluminum Alloy Pulse Variable Polarity Plasma Arc Welded Joint

Metals ◽  
2019 ◽  
Vol 9 (4) ◽  
pp. 428
Author(s):  
Guowei Li ◽  
Yahong Liang ◽  
Furong Chen ◽  
Yongquan Han ◽  
Li Sun
Keyword(s):  
Tensile Strength ◽  
Aluminum Alloy ◽  
Aging Temperature ◽  
Welded Joint ◽  
Single Stage ◽  
Precipitate Size ◽  
7075 Aluminum Alloy ◽  
Plasma Arc ◽  
Variable Polarity ◽  
Variable Polarity Plasma Arc

A 7075 aluminum alloy was successfully welded by pulsed variable polarity plasma arc welding (PVPPAW) and the single-stage aging behavior of the 7075 aluminum alloy PVPPAW joint was systematically investigated. The results demonstrated that the tensile strength of the welded joints initially increased and then decreased with the increase of the single-stage aging temperature and time. After single-stage aging at 490 °C for 80 min and at 130 °C for 24 h, the tensile strength of the welded joint was 551 MPa, which was increased by 38.5% compared to the as-welded joint. Moreover, the conductivity was 25% international annealed copper standard (IACS) at room temperature, and the resistance to stress corrosion was improved. The main strengthening phases of the weld center were η′ and η phase. The average precipitate size slightly increased with the increase of the single-stage aging temperature, but no obvious change was observed with the increase of the single-stage aging time. The area fraction was initially increased and then decreased with the increase of the single-stage aging temperature and time.

Experimental Analysis of Welding Parameters on Variable Polarity Plasma Arc Pressure

2013 ◽  
Vol 651 ◽  
pp. 355-360 ◽  
Author(s):  
Yi Jiang ◽  
Ming Liu ◽  
Yao Hui Lu ◽  
Bin Shi Xu
Keyword(s):  
Arc Welding ◽  
Gas Flow ◽  
Welding Current ◽  
Welding Parameters ◽  
Plasma Arc Welding ◽  
Plasma Arc ◽  
Arc Pressure ◽  
Variable Polarity ◽  
Reversed Polarity ◽  
Variable Polarity Plasma Arc

Variable polarity plasma arc welding has been widely used to manufacture industries. The effects of welding current and plasma gas flow as the most important parameters on variable polarity plasma arc pressure were discussed experimentally. To welding current, two experimental were designed to discuss the effects of straight polarity current and reversed polarity current on arc pressure respectively. It could be concluded that arc pressure is quadratic with welding current. To plasma gas flow, both experimental and numerical analysis are used to discuss the mechanisms of plasma gas flow to arc pressure, and it could be conclude that arc pressure is quadratic with plasma gas flow rather than linear.

Workpiece Cleaning During Variable Polarity Plasma Arc Welding of Aluminum

1994 ◽  
Vol 116 (4) ◽  
pp. 463-466 ◽  
Author(s):  
Q. Pang ◽  
T. Pang ◽  
J. C. McClure ◽  
A. C. Nunes
Keyword(s):  
Arc Welding ◽  
Dielectric Breakdown ◽  
Surface Preparation ◽  
Refractory Oxide ◽  
Plasma Arc Welding ◽  
Plasma Arc ◽  
Reverse Polarity ◽  
Variable Polarity ◽  
Variable Polarity Plasma Arc

Variable Polarity Plasma Arc welding has proved to be extremely successful in welding aluminum alloys despite their adherent refractory oxide. This success has been attributed to removal of the oxide during the reverse polarity cycle. In situ optical spectroscopy is used to measure the amount of hydrogen and oxygen in the plasma arc with a minimum detectable limit of less than 100 ppm. It was found that the amount of contamination is independent of surface preparation and torch speed. Using this information, it is proposed that the predominant mechanism for reverse polarity cleaning in aluminum is dielectric breakdown of the surface oxide ahead of the torch rather than by ion sputtering.

scholarly journals Effect of Arc Pressure on the Digging Process in Variable Polarity Plasma Arc Welding of A5052P Aluminum Alloy

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1071 ◽  
Author(s):  
Bin Xu ◽  
Shinichi Tashiro ◽  
Fan Jiang ◽  
Shujun Chen ◽  
Manabu Tanaka
Keyword(s):  
Weld Pool ◽  
High Speed ◽  
Imaging System ◽  
Physical Phenomenon ◽  
Plasma Arc ◽  
Arc Pressure ◽  
Variable Polarity ◽  
Welding Stability ◽  
Energy And Momentum ◽  
Variable Polarity Plasma Arc

The keyhole digging process associated with variable polarity plasma arc (VPPA) welding remains unclear, resulting in poor control of welding stability. The VPPA pressure directly determines the dynamics of the keyhole and weld pool in the digging process. Here, through a high speed camera, high frequency pulsed diode laser light source and X-ray transmission imaging system, we reveal the potential physical phenomenon of a keyhole weld pool. The keyhole depth changes periodically corresponding to the polarity conversion period if the current is same in the electrode negative (EN) phase and electrode positive (EP) phase. There exist three distinct regimes of keyhole and weld pool behavior in the whole digging process, due to the arc pressure attenuation and energy accumulation effect. The pressure in the EP phase is smaller than that of the EN phase, causing the fluctuation of the weld pool free surface. Based on the influence mechanism of energy and momentum transaction, the arc pressure output is balanced by separately adjusting the current in each polarity. Finally, the keyhole fluctuation during the digging process is successfully reduced and welding stability is well controlled.

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