Influence of Arc Power on Keyhole-Induced Porosity in Laser + GMAW Hybrid Welding of Aluminum Alloy: Numerical and Experimental Studies.

Guoxiang Xu,Lin Li,Baoshuai Du,Pengfei Li,Qingxian Hu,Xiaoyan Gu,Jie Zhu

doi:10.3390/ma12081328

Abstract

A three-dimensional numerical model is used to simulate heat transfer and fluid flow phenomena in fiber laser + gas metal arc welding (GMAW) hybrid welding of an aluminum alloy, which incorporates three-phase coupling and is able to depict the keyhole dynamic behavior and formation process of the keyhole-induced porosity. The temperature profiles and fluid flow fields for different arc powers are calculated and the percent porosities of weld beads were also examined under different conditions by X-ray non-destructive testing (NDT). The results showed that the computed results were in agreement with the experimental data. For hybrid welding, with raising arc power, the keyhole-induced porosity was reduced. Besides the solidification rate of the molten pool, the melt flow was also closely related to weld porosity. A relatively steady anti-clockwise vortex caused by arc forces tended to force the bubble to float upwards at the high temperature region close to the welding heat source, which benefits the escape of the gas bubble from the melt pool. When increasing the arc power, the anti-clockwise region was strengthened and the risk of the gas bubble for capture by the liquid/solid interface underneath the keyhole tip was diminished, which resulted in the lower weld percent porosity.

Highlights

Welded structures of aluminum alloys are widely used in the automobile, shipbuilding, and aerospace industries among others
One of the major problems is the keyhole-induced porosity in weld metal during the deep penetration laser welding of the aluminum alloy, which results from the instability of a laser-induced keyhole
By coupling a laser beam and an electric arc, the laser + arc hybrid welding process incorporates the advantages of both laser and arc welding processes and overcomes their individual problems [4,5], which has the potential to reduce the porosity of the aluminum alloy weld

Summary

Introduction

Welded structures of aluminum alloys are widely used in the automobile, shipbuilding, and aerospace industries among others. By coupling a laser beam and an electric arc, the laser + arc hybrid welding process incorporates the advantages of both laser and arc welding processes and overcomes their individual problems [4,5], which has the potential to reduce the porosity of the aluminum alloy weld. This obtains increasing attention in the welding of aluminum alloy [6,7,8]. To improve the stability of the welding quality, it is essential to study the mechanism of arc power on weld porosity in hybrid welding [2]

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Conclusion