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6 Behaviors of Keyhole and Weld Pool Under the Effect …
Fig. 6.12 Velocity vector distribution of liquid phase in symmetry plane at t 0 + 0.1 ms under the
effect of auxiliary gas
(a) Pressure distribution
(b) Velocity distribution
Fig. 6.13 Pressure and velocity distribution (metallic vapor inside keyhole considered) in the
symmetry plane at t 0 + 1 ms under the effect of auxiliary gas in the expansion stage: a pressure
field and b velocity field
respectively. Under the effect of pressure distribution inside the keyhole as shown in
Fig. 6.13b, the molten metal behind the keyhole opening near the lower surface and
the upper surface moves toward the axis of the keyhole, which shows a tendency to
close the keyhole. According to Fig. 6.13a, the pressure near the keyhole opening
is small, while the pressure of the areas inside the keyhole, which are far from the
opening, is large. The local hump formed on the surface of metal liquid behind the
keyhole opening in the expansion stage allows the side-blown gas to exert a greater
effect in the area. Figure 6.14b shows the velocity vector of some metal liquid of
a local hump behind the keyhole opening on the upper surface. At the end of the
expansion stage, the pressure required to continue the expansion of the keyhole is
not met, which restrains the maximum diameter of the keyhole. The period from t 0
+ 0.4 ms to t 0 + 1.2 ms in this calculation result is the expansion stage.
6 Behaviors of Keyhole and Weld Pool Under the Effect …
Fig. 6.12 Velocity vector distribution of liquid phase in symmetry plane at t 0 + 0.1 ms under the
effect of auxiliary gas
(a) Pressure distribution
(b) Velocity distribution
Fig. 6.13 Pressure and velocity distribution (metallic vapor inside keyhole considered) in the
symmetry plane at t 0 + 1 ms under the effect of auxiliary gas in the expansion stage: a pressure
field and b velocity field
respectively. Under the effect of pressure distribution inside the keyhole as shown in
Fig. 6.13b, the molten metal behind the keyhole opening near the lower surface and
the upper surface moves toward the axis of the keyhole, which shows a tendency to
close the keyhole. According to Fig. 6.13a, the pressure near the keyhole opening
is small, while the pressure of the areas inside the keyhole, which are far from the
opening, is large. The local hump formed on the surface of metal liquid behind the
keyhole opening in the expansion stage allows the side-blown gas to exert a greater
effect in the area. Figure 6.14b shows the velocity vector of some metal liquid of
a local hump behind the keyhole opening on the upper surface. At the end of the
expansion stage, the pressure required to continue the expansion of the keyhole is
not met, which restrains the maximum diameter of the keyhole. The period from t 0
+ 0.4 ms to t 0 + 1.2 ms in this calculation result is the expansion stage.