250
8 Keyhole and Weld Pool Dynamics in Laser Welding with Filler Wires
of the weld joint, thus relatively increasing the content of wire compositions in the
upper part of the weld joint.
8.6 Summary
(1) The 3-D transient mathematical model of laser welding with filler wire is
developed, which can describe the coupling effect among the wire, keyhole
and moving weld pool. And the transient behaviors of the keyhole and moving
weld pool during welding with filler wire respectively under contact transition
and free transition are systematically studied. Besides, the influence of the wire
feed rate and diameter of wire on the behaviors of the keyhole and the moving
weld pool is discussed.
(2) Under certain technical conditions, raising the wire feed rate reduces the
maximum velocity fluctuation of the fluid in the weld pool and improves the
stability of the weld pool. However, increasing the diameter of wire aggravates
the maximum velocity fluctuation of the fluid in the weld pool, thus weakening the stability of the weld pool. For the laser welding with filler wire in
case of the wire in front of the keyhole, under general conditions, although the
moving weld pool is more stable than that in single-beam laser welding under
the same conditions, the keyhole is more unstable than that in the single-beam
laser welding.
(3) The mathematical model of the dynamic dilution process of the moving weld
pool in non-self-melting laser welding process is developed. With the model,
a systematic numerical simulation study on the dynamic dilution behaviors of
wire compositions respectively in the quasi-steady moving weld pool and in the
transient moving weld pool is conducted, and a laser welding experiment on the
powder coated at the surface of parent metal is designed to verify the simulation
results. The verification shows that it is feasible to predict the quantitative
distribution of the chemical compositions of wire in the moving weld pool in
the solidification instant. The establishment of this model provides an idea to
control the mechanical properties of a weld joint by precisely controlling the
distribution of the chemical compositions of wire in the weld joint.
(4) In the non-self-melting laser welding process, convection is the primary factor
for the wire compositions being diluted by the moving weld pool. The highspeed flow towards the depth of penetration caused by the flow that bypasses
the keyhole and the recoil pressure is the primary factor for the dilution of the
weld pool. The content of the chemical compositions of wire reaches a local
maximum or minimum where there is vortex flow in the weld pool.
8 Keyhole and Weld Pool Dynamics in Laser Welding with Filler Wires
of the weld joint, thus relatively increasing the content of wire compositions in the
upper part of the weld joint.
8.6 Summary
(1) The 3-D transient mathematical model of laser welding with filler wire is
developed, which can describe the coupling effect among the wire, keyhole
and moving weld pool. And the transient behaviors of the keyhole and moving
weld pool during welding with filler wire respectively under contact transition
and free transition are systematically studied. Besides, the influence of the wire
feed rate and diameter of wire on the behaviors of the keyhole and the moving
weld pool is discussed.
(2) Under certain technical conditions, raising the wire feed rate reduces the
maximum velocity fluctuation of the fluid in the weld pool and improves the
stability of the weld pool. However, increasing the diameter of wire aggravates
the maximum velocity fluctuation of the fluid in the weld pool, thus weakening the stability of the weld pool. For the laser welding with filler wire in
case of the wire in front of the keyhole, under general conditions, although the
moving weld pool is more stable than that in single-beam laser welding under
the same conditions, the keyhole is more unstable than that in the single-beam
laser welding.
(3) The mathematical model of the dynamic dilution process of the moving weld
pool in non-self-melting laser welding process is developed. With the model,
a systematic numerical simulation study on the dynamic dilution behaviors of
wire compositions respectively in the quasi-steady moving weld pool and in the
transient moving weld pool is conducted, and a laser welding experiment on the
powder coated at the surface of parent metal is designed to verify the simulation
results. The verification shows that it is feasible to predict the quantitative
distribution of the chemical compositions of wire in the moving weld pool in
the solidification instant. The establishment of this model provides an idea to
control the mechanical properties of a weld joint by precisely controlling the
distribution of the chemical compositions of wire in the weld joint.
(4) In the non-self-melting laser welding process, convection is the primary factor
for the wire compositions being diluted by the moving weld pool. The highspeed flow towards the depth of penetration caused by the flow that bypasses
the keyhole and the recoil pressure is the primary factor for the dilution of the
weld pool. The content of the chemical compositions of wire reaches a local
maximum or minimum where there is vortex flow in the weld pool.