8.3 Keyhole and Weld Pool Dynamics in Welding with Filler Wires
223
1.75 m/s, with the maximum value of 2.6 m/s and the minimum value of 1.6 m/s.
The quantitative analysis indicates that compared with the free transition, the contact
transition can better promote the stability of the flow in the weld pool of laser welding
during the wire addition process. According to the analysis based on Fig. 8.19, it is
mainly because the addition of wire increases the width and length of the weld pool
around the keyhole, that is, the flow range around the keyhole, which further reduces
the maximum speed fluctuation of the weld pool and improves the stability of the
weld pool.
The above simulation results show that under the current research conditions, the
process of single-beam laser welding can bring about a greater penetration depth
than the process of laser welding with filler wires. However, the weld pool has a
better stability in the process of laser welding with filler wires than the process of
single-beam laser welding, no matter the wire enters the weld pool in free transition
mode or contact transition mode. Relatively speaking, the moving weld pool has the
optimal stability in contact transition.
8.4 Instability of Keyhole and Weld Pool in Welding
with Filler Wires
8.4.1 Weld Pool Dynamics in Single Beam Laser Welding
and Laser Welding with Filler Wires
In this section, the weld pool dynamics in the process of single-beam laser welding
and the process of laser welding with filler wires is studied through a high-speed
photography test to qualitatively verify some conclusions in Sect. 8.3.1. In the
welding test, the equipment used is YLR-4000 type fiber laser, with the material
of aluminum alloy. The diameter of wire is 1 mm and the material is SA1-Mg5. To
avoid oxidation of aluminum alloy weld pool during welding, argon is adopted for
protection.
Figure 8.21 shows typical images of the weld pool surface during single deep
penetration laser welding. It can be seen from the figure that the surface of the weld
pool is very unsmooth, and the weld pool fluctuates violently. The subsidence on the
surface of the weld pool is relatively serious, and there are two serious subsidence
occurrences near the opening of the keyhole and the tail of the weld pool. The above
test results indicate that the stability of the weld pool is poor during the single-beam
laser welding of aluminum alloy.
Figure 8.22 shows typical images of the weld pool surface during laser welding
with filler wires. As can be seen from the figure, due to the addition of the wire, the
fluctuation of the surface of the weld pool is significantly reduced, and the unevenness
of the subsidence on the surface of the weld pool is more moderate compared with
that of the single-beam laser welding.
223
1.75 m/s, with the maximum value of 2.6 m/s and the minimum value of 1.6 m/s.
The quantitative analysis indicates that compared with the free transition, the contact
transition can better promote the stability of the flow in the weld pool of laser welding
during the wire addition process. According to the analysis based on Fig. 8.19, it is
mainly because the addition of wire increases the width and length of the weld pool
around the keyhole, that is, the flow range around the keyhole, which further reduces
the maximum speed fluctuation of the weld pool and improves the stability of the
weld pool.
The above simulation results show that under the current research conditions, the
process of single-beam laser welding can bring about a greater penetration depth
than the process of laser welding with filler wires. However, the weld pool has a
better stability in the process of laser welding with filler wires than the process of
single-beam laser welding, no matter the wire enters the weld pool in free transition
mode or contact transition mode. Relatively speaking, the moving weld pool has the
optimal stability in contact transition.
8.4 Instability of Keyhole and Weld Pool in Welding
with Filler Wires
8.4.1 Weld Pool Dynamics in Single Beam Laser Welding
and Laser Welding with Filler Wires
In this section, the weld pool dynamics in the process of single-beam laser welding
and the process of laser welding with filler wires is studied through a high-speed
photography test to qualitatively verify some conclusions in Sect. 8.3.1. In the
welding test, the equipment used is YLR-4000 type fiber laser, with the material
of aluminum alloy. The diameter of wire is 1 mm and the material is SA1-Mg5. To
avoid oxidation of aluminum alloy weld pool during welding, argon is adopted for
protection.
Figure 8.21 shows typical images of the weld pool surface during single deep
penetration laser welding. It can be seen from the figure that the surface of the weld
pool is very unsmooth, and the weld pool fluctuates violently. The subsidence on the
surface of the weld pool is relatively serious, and there are two serious subsidence
occurrences near the opening of the keyhole and the tail of the weld pool. The above
test results indicate that the stability of the weld pool is poor during the single-beam
laser welding of aluminum alloy.
Figure 8.22 shows typical images of the weld pool surface during laser welding
with filler wires. As can be seen from the figure, due to the addition of the wire, the
fluctuation of the surface of the weld pool is significantly reduced, and the unevenness
of the subsidence on the surface of the weld pool is more moderate compared with
that of the single-beam laser welding.