196
7 Keyhole and Weld Pool Dynamics in Dual-Beam Laser Welding
keyhole depth is 2.23 mm, 1.70 mm and 1.45 mm, respectively. It can be seen that
the keyhole depth decreases as the welding speed increases. Besides, in parallel dual
beam welding, the keyhole shape is generally irregular, and protrusions are generated
in many places on the wall surface of the keyhole.
7.4.2.2 Influence of Beam Spot Spacing on the Evolution Process
of Keyhole Shape
Figure 7.14 shows the keyhole shape in parallel dual beam welding with beam spot
spacing of 0.25 mm, 0.5 mm and 1.0 mm respectively at 35 ms. It can be seen that:
➀ when the beam spot spacing is relatively small, two beams will produce a keyhole
together in the same weld pool, as shown in Fig. 7.14a, and the keyhole has a high
depth and a small opening; ➁ as the spot spacing increases, the two beams create a
keyhole respectively in the same weld pool, with the front wall of the keyhole created
by the first beam closely connected with the rear wall of the keyhole created by the
second beam, as shown in Fig. 7.14b, and at this point, the depth of the keyhole
decreases and the radius of the opening increases; ➂ when the beam spot spacing is
too large, the two keyholes will be separated, and two relatively independent keyholes
will be formed in the same weld pool, or two separate weld pools and keyholes will
be formed, as shown in Fig. 7.14c. At this point, the depth of the weld pool decreases,
as well as the depth of keyhole and the radius of the opening. Therefore, it can be seen
that in parallel dual beam welding, with the increase of the spot spacing, the keyhole
depth decreases, while the radius of the opening increases. When the beam spot
spacing is too large, the two beams will form two relatively independent keyholes in
the weld pool, and the welding mechanism will also change.
7.4.2.3 Stages of Keyhole Depth Oscillation
Figure 7.15 shows the variation curves of keyhole depth with time in parallel dual
Temperature
T/K
(a) Beam spot spacing of 0.25 mm (b) Beam spot spacing of 0.5 mm (c) Beam spot spacing of 1.0 mm
Fig. 7.14 Shape and temperature distribution of keyhole created by parallel dual beams with
different beam spot spacing
7 Keyhole and Weld Pool Dynamics in Dual-Beam Laser Welding
keyhole depth is 2.23 mm, 1.70 mm and 1.45 mm, respectively. It can be seen that
the keyhole depth decreases as the welding speed increases. Besides, in parallel dual
beam welding, the keyhole shape is generally irregular, and protrusions are generated
in many places on the wall surface of the keyhole.
7.4.2.2 Influence of Beam Spot Spacing on the Evolution Process
of Keyhole Shape
Figure 7.14 shows the keyhole shape in parallel dual beam welding with beam spot
spacing of 0.25 mm, 0.5 mm and 1.0 mm respectively at 35 ms. It can be seen that:
➀ when the beam spot spacing is relatively small, two beams will produce a keyhole
together in the same weld pool, as shown in Fig. 7.14a, and the keyhole has a high
depth and a small opening; ➁ as the spot spacing increases, the two beams create a
keyhole respectively in the same weld pool, with the front wall of the keyhole created
by the first beam closely connected with the rear wall of the keyhole created by the
second beam, as shown in Fig. 7.14b, and at this point, the depth of the keyhole
decreases and the radius of the opening increases; ➂ when the beam spot spacing is
too large, the two keyholes will be separated, and two relatively independent keyholes
will be formed in the same weld pool, or two separate weld pools and keyholes will
be formed, as shown in Fig. 7.14c. At this point, the depth of the weld pool decreases,
as well as the depth of keyhole and the radius of the opening. Therefore, it can be seen
that in parallel dual beam welding, with the increase of the spot spacing, the keyhole
depth decreases, while the radius of the opening increases. When the beam spot
spacing is too large, the two beams will form two relatively independent keyholes in
the weld pool, and the welding mechanism will also change.
7.4.2.3 Stages of Keyhole Depth Oscillation
Figure 7.15 shows the variation curves of keyhole depth with time in parallel dual
Temperature
T/K
(a) Beam spot spacing of 0.25 mm (b) Beam spot spacing of 0.5 mm (c) Beam spot spacing of 1.0 mm
Fig. 7.14 Shape and temperature distribution of keyhole created by parallel dual beams with
different beam spot spacing