204
8 Keyhole and Weld Pool Dynamics in Laser Welding with Filler Wires
laser beam action area at certain speed, the wire melts after being heated, the molten
metal enters the parent metal weld pool area, and finally the weld joint is formed
after solidification of the weld pool. Under the appropriate technical condition, by
adding the wire, the weld joint compositions and organization can be controlled, any
welding defects can be restrained, and the tolerance of pre-weld assembly clearance
can be increased.
With the laser welding with filler wires—non self-fluxing welding process as a
study object, this chapter introduces the simulation mathematical model for keyhole
and weld pool dynamics in laser welding with filler wires to reproduce the heat
transfer, flow, free interface motion, and other transient coupling behaviors between
wire, keyhole, and moving weld pool under different technical conditions, focusing
on interpretation of keyhole and weld pool stability, and related mechanisms during
laser welding with filler wires, followed by preliminary exploration of the motion law
of wire element in the weld pool, as well as quantitative prediction of the distribution
characteristics of wire chemical elements in the weld joint.
8.2 Multiphase Transient Coupling Model in Laser
Welding with Filler Wires
8.2.1 Mathematical Model of Wire Melting
In the chapter, addition of droplet is processed into interval increase of enthalpy and
wire composition in the weld joint. Meantime, the enthalpy increment carried by the
droplet is regarded as a volume heat source which has the following characteristic
parameters: radius (R v ), height (d), and energy density (S v ), including the interaction
between molten droplet and weld pool under different welding conditions. Assumed
that the radius of the volume heat source is 2.7 times the radius of the droplet, the
height is calculated through the following equation based on conservation of energy:
d = h v − x v + D d
(8.1)
where, h v —The estimated height of the cavity formed by impact of the molten
droplet;
x v —The moving distance of the center of the latter droplet during collision of two
continuous falling droplets;
D d —Diameter of the droplet.
The effective input heat of the molten droplet Q a is defined to be:
Q a = ρπr
2
w w f H d
(8.2)
where, ρ—Density;
8 Keyhole and Weld Pool Dynamics in Laser Welding with Filler Wires
laser beam action area at certain speed, the wire melts after being heated, the molten
metal enters the parent metal weld pool area, and finally the weld joint is formed
after solidification of the weld pool. Under the appropriate technical condition, by
adding the wire, the weld joint compositions and organization can be controlled, any
welding defects can be restrained, and the tolerance of pre-weld assembly clearance
can be increased.
With the laser welding with filler wires—non self-fluxing welding process as a
study object, this chapter introduces the simulation mathematical model for keyhole
and weld pool dynamics in laser welding with filler wires to reproduce the heat
transfer, flow, free interface motion, and other transient coupling behaviors between
wire, keyhole, and moving weld pool under different technical conditions, focusing
on interpretation of keyhole and weld pool stability, and related mechanisms during
laser welding with filler wires, followed by preliminary exploration of the motion law
of wire element in the weld pool, as well as quantitative prediction of the distribution
characteristics of wire chemical elements in the weld joint.
8.2 Multiphase Transient Coupling Model in Laser
Welding with Filler Wires
8.2.1 Mathematical Model of Wire Melting
In the chapter, addition of droplet is processed into interval increase of enthalpy and
wire composition in the weld joint. Meantime, the enthalpy increment carried by the
droplet is regarded as a volume heat source which has the following characteristic
parameters: radius (R v ), height (d), and energy density (S v ), including the interaction
between molten droplet and weld pool under different welding conditions. Assumed
that the radius of the volume heat source is 2.7 times the radius of the droplet, the
height is calculated through the following equation based on conservation of energy:
d = h v − x v + D d
(8.1)
where, h v —The estimated height of the cavity formed by impact of the molten
droplet;
x v —The moving distance of the center of the latter droplet during collision of two
continuous falling droplets;
D d —Diameter of the droplet.
The effective input heat of the molten droplet Q a is defined to be:
Q a = ρπr
2
w w f H d
(8.2)
where, ρ—Density;