210
8 Keyhole and Weld Pool Dynamics in Laser Welding with Filler Wires
Fig. 8.4 Weld pool morphology of longitudinal section during the droplet free transition process
droplet will flow into the keyhole along the front wall of the keyhole. On the other
hand, due to overheating of the droplet, the carried heat will melt the parent metal in
the front part of the keyhole, hence to thicken the weld pool close the front wall of
the keyhole. The above two factors tend to aggravate the front boss phenomenon of
the keyhole wall, as shown in Fig. 8.3d through f. Since the droplet falling interval
is 9.64 ms, the second droplet appears in Fig. 8.3e.
Figure 8.4 is the weld pool transient morphology on the longitudinal section
during the droplet free transition. In the figure, the green part (other than the droplet
part) represents the keyhole, and the red part between parent metal and keyhole is
the weld pool.
As it can be seen from Fig. 8.4, the weld pool is also gradually forming while
the keyhole is forming. Over time, the liquid in the weld pool at the back edge of
the keyhole gradually increases by accumulation, and therefore, it can be inferred
that the weld pool finally reaches the quasi-steady state when the welding speed is
consistent with the solidification rate at the back edge of the weld pool. Furthermore,
addition of the droplet can effectively increase the volume of the weld pool in front
wall of the keyhole.
Figure 8.5 is the transient evolution process of the 3D free interface morphology
during the metal-droplet transition process. In the figure, the color represents temperature, and the blue plane represents the surface of the parent metal. According to
Figs.8.3 and 8.4, it’s found that the droplet spreads out after falling to the surface of
the parent metal, and scatters all round. As the droplet is very close to the keyhole,
some droplets are easy to flow into the keyhole, which may aggravate instability of
the keyhole. It shows from analysis and discussion of the above simulation results
that, the metal-droplet transition mathematical model developed in the chapter can
reasonably simulate the complicated transient interaction between droplet, keyhole,
and moving weld pool during the laser welding with filler wires. Meantime, the
above-mentioned results also show that, under the technical condition of the wire
8 Keyhole and Weld Pool Dynamics in Laser Welding with Filler Wires
Fig. 8.4 Weld pool morphology of longitudinal section during the droplet free transition process
droplet will flow into the keyhole along the front wall of the keyhole. On the other
hand, due to overheating of the droplet, the carried heat will melt the parent metal in
the front part of the keyhole, hence to thicken the weld pool close the front wall of
the keyhole. The above two factors tend to aggravate the front boss phenomenon of
the keyhole wall, as shown in Fig. 8.3d through f. Since the droplet falling interval
is 9.64 ms, the second droplet appears in Fig. 8.3e.
Figure 8.4 is the weld pool transient morphology on the longitudinal section
during the droplet free transition. In the figure, the green part (other than the droplet
part) represents the keyhole, and the red part between parent metal and keyhole is
the weld pool.
As it can be seen from Fig. 8.4, the weld pool is also gradually forming while
the keyhole is forming. Over time, the liquid in the weld pool at the back edge of
the keyhole gradually increases by accumulation, and therefore, it can be inferred
that the weld pool finally reaches the quasi-steady state when the welding speed is
consistent with the solidification rate at the back edge of the weld pool. Furthermore,
addition of the droplet can effectively increase the volume of the weld pool in front
wall of the keyhole.
Figure 8.5 is the transient evolution process of the 3D free interface morphology
during the metal-droplet transition process. In the figure, the color represents temperature, and the blue plane represents the surface of the parent metal. According to
Figs.8.3 and 8.4, it’s found that the droplet spreads out after falling to the surface of
the parent metal, and scatters all round. As the droplet is very close to the keyhole,
some droplets are easy to flow into the keyhole, which may aggravate instability of
the keyhole. It shows from analysis and discussion of the above simulation results
that, the metal-droplet transition mathematical model developed in the chapter can
reasonably simulate the complicated transient interaction between droplet, keyhole,
and moving weld pool during the laser welding with filler wires. Meantime, the
above-mentioned results also show that, under the technical condition of the wire