226
8 Keyhole and Weld Pool Dynamics in Laser Welding with Filler Wires
8.4.3 Mechanism of Keyholes Instability in Welding
with Filler Wires
According to the numerical simulation results in Sect. 8.3, in the process of laser
welding with filler wires without complete penetration, when the wire is located in
front of the keyhole, the use of welding with filler wire can stabilize the stability
of the moving weld pool; however, because the metallic liquid may flow into the
keyhole or be pushed into the keyhole by recoil pressure along the forearm of the
keyhole, whether the wire enters the weld pool in the form of molten drop or liquid
bridge, there is a tendency to increase the lug boss phenomenon of the front wall of
the keyhole, that is to say, the addition of the wire may increase the instability of
keyholes.
In order to verify the rationality of the mechanism, the recent test work on laser
welding with filler wires by Dr. Yu Yangchun from Huazhong University of Science
and Technology (HUST) is quoted for verification, which is shown below. In their
welding tests, the parent metal is 4 mm thick 5A06 aluminum alloy plate, and the
additive is SA1-Mg5 wire with a diameter of 1 mm. In addition, YLR4000-type fiber
laser of IPG company is used for welding. The defocusing amount is set to zero, and
single laser welding and laser welding with filler wires tests are performed separately
during the welding process. The test parameters and technical parameters used are
shown in Table 8.7. Figure 8.24 shows the corresponding pictures of the longitudinal
section and cross section of the weld joint.
It can be seen from Fig. 8.24 that the filler wire penetration under the condition
of the same power and welding speed is a little shallower than that of single-beam
laser welding, which is consistent with the simulation results of Sect. 8.3.7 in this
Table 8.7 Technical parameters of laser welding with filler wires
No Laser power/kw Welding speed/ (m/min) Wire feed rate/(m/min) Plate thickness/mm
1
3
2
0
4
2
3
2
4
4
3
3.5
1.2
7
4
4
3.8
1.2
7
4
Fig. 8.24 Longitudinal section and cross section (weld joint) of the weld joint under the
corresponding process in Table 8.7
8 Keyhole and Weld Pool Dynamics in Laser Welding with Filler Wires
8.4.3 Mechanism of Keyholes Instability in Welding
with Filler Wires
According to the numerical simulation results in Sect. 8.3, in the process of laser
welding with filler wires without complete penetration, when the wire is located in
front of the keyhole, the use of welding with filler wire can stabilize the stability
of the moving weld pool; however, because the metallic liquid may flow into the
keyhole or be pushed into the keyhole by recoil pressure along the forearm of the
keyhole, whether the wire enters the weld pool in the form of molten drop or liquid
bridge, there is a tendency to increase the lug boss phenomenon of the front wall of
the keyhole, that is to say, the addition of the wire may increase the instability of
keyholes.
In order to verify the rationality of the mechanism, the recent test work on laser
welding with filler wires by Dr. Yu Yangchun from Huazhong University of Science
and Technology (HUST) is quoted for verification, which is shown below. In their
welding tests, the parent metal is 4 mm thick 5A06 aluminum alloy plate, and the
additive is SA1-Mg5 wire with a diameter of 1 mm. In addition, YLR4000-type fiber
laser of IPG company is used for welding. The defocusing amount is set to zero, and
single laser welding and laser welding with filler wires tests are performed separately
during the welding process. The test parameters and technical parameters used are
shown in Table 8.7. Figure 8.24 shows the corresponding pictures of the longitudinal
section and cross section of the weld joint.
It can be seen from Fig. 8.24 that the filler wire penetration under the condition
of the same power and welding speed is a little shallower than that of single-beam
laser welding, which is consistent with the simulation results of Sect. 8.3.7 in this
Table 8.7 Technical parameters of laser welding with filler wires
No Laser power/kw Welding speed/ (m/min) Wire feed rate/(m/min) Plate thickness/mm
1
3
2
0
4
2
3
2
4
4
3
3.5
1.2
7
4
4
3.8
1.2
7
4
Fig. 8.24 Longitudinal section and cross section (weld joint) of the weld joint under the
corresponding process in Table 8.7