7.5 Summary
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decreases too. When the welding speed increases to a certain value, the keyhole
is even to be in a stable status.
(3) In the process of parallel dual beam welding, with the increase of the laser-spot
spacing, the keyhole depth decreases but the radius of the opening increases
generally. When the laser-spot spacing is too large, two beams will form two
relatively independent keyholes in the weld pool, and the welding mechanism
will also change. In addition, if the laser-spot spacing is too large or too small,
the keyhole depth oscillation amplitude will increase, and when the spacing is
too large, the weld penetration depth will fluctuate greatly.
(4) In tandem dual beam laser welding, with the increase of the beam spacing, the
welding process experiences the change from a single keyhole, to one opening
but different hole bottoms, and to two independent keyholes. In the general
process of welding with one opening but different hole bottoms, the keyhole
in the rear is larger than the one in the front due to the effect of preheating.
(5) The frequency of keyhole depth oscillation in tandem dual beam laser welding
is several kilohertz, which is equivalent to that for single beam laser welding.
The keyhole depth oscillation amplitude is smaller than that for single beam
laser welding, and the keyhole depth oscillation gradually becomes stable with
the increase of the welding speed.
(6) Under the same heat input conditions, the flow in the weld pool for tandem
dual beam laser welding is more stable than the flow in the weld pool for single
beam laser welding. For dual beam laser welding, the power density in the weld
pool is lower, the superficial area of the weld joint larger, the surface tension
effect weaker, and the weld pool during the welding process is more stable.
(7) Compared with single beam laser welding, the process stability mechanism of
dual beam laser welding is not only caused by the degassing effect of the larger
keyhole, but also by the combined effect of several conducive physical factors.
201
decreases too. When the welding speed increases to a certain value, the keyhole
is even to be in a stable status.
(3) In the process of parallel dual beam welding, with the increase of the laser-spot
spacing, the keyhole depth decreases but the radius of the opening increases
generally. When the laser-spot spacing is too large, two beams will form two
relatively independent keyholes in the weld pool, and the welding mechanism
will also change. In addition, if the laser-spot spacing is too large or too small,
the keyhole depth oscillation amplitude will increase, and when the spacing is
too large, the weld penetration depth will fluctuate greatly.
(4) In tandem dual beam laser welding, with the increase of the beam spacing, the
welding process experiences the change from a single keyhole, to one opening
but different hole bottoms, and to two independent keyholes. In the general
process of welding with one opening but different hole bottoms, the keyhole
in the rear is larger than the one in the front due to the effect of preheating.
(5) The frequency of keyhole depth oscillation in tandem dual beam laser welding
is several kilohertz, which is equivalent to that for single beam laser welding.
The keyhole depth oscillation amplitude is smaller than that for single beam
laser welding, and the keyhole depth oscillation gradually becomes stable with
the increase of the welding speed.
(6) Under the same heat input conditions, the flow in the weld pool for tandem
dual beam laser welding is more stable than the flow in the weld pool for single
beam laser welding. For dual beam laser welding, the power density in the weld
pool is lower, the superficial area of the weld joint larger, the surface tension
effect weaker, and the weld pool during the welding process is more stable.
(7) Compared with single beam laser welding, the process stability mechanism of
dual beam laser welding is not only caused by the degassing effect of the larger
keyhole, but also by the combined effect of several conducive physical factors.