Process stabilization by dual focus laser welding of aluminum alloys for car body

Abstract

Aluminum alloys were welded using dual focus beams formed with two Nd:YAG lasers with the aim ofobtaining a stable welding process. The relationship between the configuration of the spot beams and the quality of the weld beads was investigated using X-ray and high-speed camera observations. The number ofpores was clearly related to the ratio of the keyhole depth to the keyhole opening. A larger keyhole opening and/or a shallower keyhole depth resulted in a smaller number of pores caused by instability of the weld pool. Based on the investigation, a car body component was welded with a dual focus beam system. The results show that aluminum car body panels can be welded stably at high speed with little distortion under optimum conditions.

Self-consistent modeling of keyhole and weld pool dynamics in tandem dual beam laser welding of aluminum alloy

“…This qualitatively agrees well with previous experimental studies that a more stable weld pool can be obtained during dual beam laser welding (Shibata et al, 2003;Xie, 2002a, b). Previously, Relative to single beam laser welding, a major improving factor of fluid flow of dual beam laser welding was the difference of vapor plume dynamics between the two processes (Shibata et al, 2003;Xie, 2002a, b). Nevertheless, the friction effect of vapor plume on the keyhole wall is neglected in present model.…”

“…Hence the surface tension force on the dynamic keyhole wall becomes smaller, which means the keyhole becomes more stable in the keyhole welding mode. This theoretical finding is also in good agreement with the X-Ray imaging experimental results of Shibata et al (2003). In their study, fewer pores are found in high welding speed conditions during dual beam laser welding, which indeed suggests that the keyhole is more stable.…”

“…This unstable nature of keyhole shown here is consistent with previous experimental investigations. For example, Xie (2002a), Iwase et al (2000), Shibata et al (2003) and Deutsch et al (2003) found small irregular pores induced by keyhole dynamics are existed in tandem dual beam laser welds. Li et al (2008) proved that the plasma plume is also existed in dynamic oscillating during tandem dual beam laser welding.…”

“…The welding experiments are used from Xie (2002b) and Shibata et al (2003). The experimental process parameters are listed in Table 2.…”

“…It was suggested that the welding process becomes unstable when a single beam or a short beam distance is used, and the degassing effect of an enlarged keyhole aperture in dual A c c e p t e d M a n u s c r i p t 4 beam laser welding is responsible for the improvement of process instability. Shibata et al (2003) studied the pore characteristics during tandem dual beam Nd:YAG laser welding of automobile used aluminum alloys using a micro-focus in-situ X-Ray imaging apparatus. It was shown that the number of pores is closely related to the ratio of keyhole depth to the keyhole opening, and an enlarged keyhole opening and/or a shallow keyhole depth results in smaller pores.…”