172
6 Behaviors of Keyhole and Weld Pool Under the Effect …
(a) Complete picture of the weld pool
(b) Side of the weld pool
(c) Front of the weld pool
Weld reinforcement
Undercut
Fig. 6.7 Surface shape of the weld pool at 7 ms under the effect of auxiliary gas
6.3.2 Behaviors of the Keyhole and Weld Pool Under
the Combined Effects of Metallic Vapors
and Side-Blown Gas
Figure 6.11 shows the transient evolution of the keyhole and weld pool when the
side-blown gas is applied. In the figure, the red region indicates liquid metal, and the
blue region is a gas phase region. The initial time t 0 = 3.5 ms refers to the moment
when metal vapor is generated at the beginning. Figure 6.11 also shows the transient
behavior of the keyhole and weld pool under the action of metallic vapor in 2.7 ms
is given in chronological order. As can be seen from Fig. 6.11, the evolution of
keyhole and weld pool consists of three typical stages: initial stage, expansion stage
and refilling stage. It is assumed that the keyhole is formed instantaneously in the
welding process and the whole welding process is the constant cycles of these three
stages.
In the initial stage of the formation of metallic vapor in the keyhole, the liquid
metal surrounding the keyhole flows radially outwards due to the impact of metallic
vapor generated by the strong evaporation. Figure 6.12 shows the velocity vector
6 Behaviors of Keyhole and Weld Pool Under the Effect …
(a) Complete picture of the weld pool
(b) Side of the weld pool
(c) Front of the weld pool
Weld reinforcement
Undercut
Fig. 6.7 Surface shape of the weld pool at 7 ms under the effect of auxiliary gas
6.3.2 Behaviors of the Keyhole and Weld Pool Under
the Combined Effects of Metallic Vapors
and Side-Blown Gas
Figure 6.11 shows the transient evolution of the keyhole and weld pool when the
side-blown gas is applied. In the figure, the red region indicates liquid metal, and the
blue region is a gas phase region. The initial time t 0 = 3.5 ms refers to the moment
when metal vapor is generated at the beginning. Figure 6.11 also shows the transient
behavior of the keyhole and weld pool under the action of metallic vapor in 2.7 ms
is given in chronological order. As can be seen from Fig. 6.11, the evolution of
keyhole and weld pool consists of three typical stages: initial stage, expansion stage
and refilling stage. It is assumed that the keyhole is formed instantaneously in the
welding process and the whole welding process is the constant cycles of these three
stages.
In the initial stage of the formation of metallic vapor in the keyhole, the liquid
metal surrounding the keyhole flows radially outwards due to the impact of metallic
vapor generated by the strong evaporation. Figure 6.12 shows the velocity vector