216
8 Keyhole and Weld Pool Dynamics in Laser Welding with Filler Wires
Table 8.4 Technical parameters of laser welding with filler wires
Laser power/kw Laser spot radius/mm Defocusing amount/mm Welding speed/ (m/min)
1.5
0.2
0
3
Table 8.5 Numerical simulation parameters
Grid quantity
Spatial step/m Time step/s Initial temperature of
parent metal/K
Ambient temperature/K
160 × 60 × 80 3.0 × 10 –5
3.0 × 10 –6 300
300
Table 8.6 Thermophysical parameters for parent metal
Density
/(kg/m 3 )
Specific
heat
capacity
/[J/(kg•K)]
Thermal
conductivity
/[W/(m•K)]
Liquidus
temperature/K
Solidus
temperature/K
Latent
heat of
melting
/(J/kg)
Latent heat
of
evaporation
/(J/kg)
Boiling
point
/K
4000
660
25
1928
1878
3.7 ×
10 5
8.9 × 10 6
3315
Fig. 8.12 Transient keyhole morphology on the longitudinal section of the molten droplet contact
transition process
the welding direction is from right to left, the red part represents gas, and the blue
part represents droplet ad parent metal. Figure 8.12a through Fig. 8.12f show the free
interface morphology on the longitudinal section at the moment of 0 ms, 1.78 ms,
4.63 ms, 7.51 ms, 11.44 ms and 15.15 ms, respectively. It can be seen from the figures
that the keyhole is gradually formed with the advancing of the welding process;
meanwhile, the molten droplet fluid gradually flows into the keyhole along the wall
surface of the keyhole, leading to a tendency of keyhole closing at the moment of
15.15 ms. Therefore, similar to free transition, the flow of the molten droplet to
the weld pool in contact transition mode under given technical condition may also
intensify the instability of the keyhole.
Figure 8.13 shows the evolution process of the weld pool. In the figure, the green
8 Keyhole and Weld Pool Dynamics in Laser Welding with Filler Wires
Table 8.4 Technical parameters of laser welding with filler wires
Laser power/kw Laser spot radius/mm Defocusing amount/mm Welding speed/ (m/min)
1.5
0.2
0
3
Table 8.5 Numerical simulation parameters
Grid quantity
Spatial step/m Time step/s Initial temperature of
parent metal/K
Ambient temperature/K
160 × 60 × 80 3.0 × 10 –5
3.0 × 10 –6 300
300
Table 8.6 Thermophysical parameters for parent metal
Density
/(kg/m 3 )
Specific
heat
capacity
/[J/(kg•K)]
Thermal
conductivity
/[W/(m•K)]
Liquidus
temperature/K
Solidus
temperature/K
Latent
heat of
melting
/(J/kg)
Latent heat
of
evaporation
/(J/kg)
Boiling
point
/K
4000
660
25
1928
1878
3.7 ×
10 5
8.9 × 10 6
3315
Fig. 8.12 Transient keyhole morphology on the longitudinal section of the molten droplet contact
transition process
the welding direction is from right to left, the red part represents gas, and the blue
part represents droplet ad parent metal. Figure 8.12a through Fig. 8.12f show the free
interface morphology on the longitudinal section at the moment of 0 ms, 1.78 ms,
4.63 ms, 7.51 ms, 11.44 ms and 15.15 ms, respectively. It can be seen from the figures
that the keyhole is gradually formed with the advancing of the welding process;
meanwhile, the molten droplet fluid gradually flows into the keyhole along the wall
surface of the keyhole, leading to a tendency of keyhole closing at the moment of
15.15 ms. Therefore, similar to free transition, the flow of the molten droplet to
the weld pool in contact transition mode under given technical condition may also
intensify the instability of the keyhole.
Figure 8.13 shows the evolution process of the weld pool. In the figure, the green