8.5 Dynamic Dilution Behavior of Moving Weld Pools …
229
In order to obtain the information of the flow field, temperature field and free
interface of keyholes in the moving weld pool, boundary conditions such as the
pressure, viscous stress and energy similar to that in Eqs. (8.13)–(8.16) must be
considered in the simulation process. In addition to the above boundary conditions,
the initial boundary conditions of the chemical compositions of the wire must also
be considered to simulate the dynamic dilution process of the chemical compositions
of the wire.
In theory, the simulation results of the keyhole and weld pool in the welding
with filler wire in this chapter can provide initial conditions such as composition for
dynamic dilution research. However, because the physical mechanism of the laser
welding with filler wires is very complicated, if the simulation results in this chapter
are used as initial conditions, it will bring great difficulties to the test verification of
the simulation results of the dynamic dilution research. In order to facilitate the test
verification of the established dynamic dilution simulation of the moving weld pool,
an idealized boundary condition is set up and a layer of wire powder is required
to be laid on the surface of the moving weld pool. That is, at these locations, the
concentration values of the chemical compositions of the wire have the following
boundary conditions
C = 1.0
(8.19)
8.5.2 Dynamic Dilution Behavior in Quasi-Steady Weld Pools
As the laser welding process goes on, the moving weld pool will enter a relatively
stable state, and the obtained weld joint tends to be in a relatively stable shape, that is,
the welding process enters the quasi-steady state. After the welding process reaches
the quasi-steady state, on the one hand, the melted wire material will continuously
enter the weld pool from the melting front of the front end of the moving weld
pool; on the other hand, the chemical compositions carried in the wire will gradually
leave the moving weld pool from the solidification front of the moving weld pool.
Therefore, studying the dilution process of the chemical compositions of the wire
in the moving weld pool when the welding process reaches the quasi-steady state
is of great significance to explain the dynamic dilution mechanism of the moving
weld pool in the laser welding process and reveal the distribution law of the chemical
compositions of wire inside the weld joint.
8.5.2.1 Calculation for Quasi-Steady Moving Weld Pools
By solving the transient coupling model of laser welding and laser welding with filler
wires, important information such as the three-dimensional morphology, temperature
field, flow field and keyhole morphology of the quasi-steady moving weld pool during
229
In order to obtain the information of the flow field, temperature field and free
interface of keyholes in the moving weld pool, boundary conditions such as the
pressure, viscous stress and energy similar to that in Eqs. (8.13)–(8.16) must be
considered in the simulation process. In addition to the above boundary conditions,
the initial boundary conditions of the chemical compositions of the wire must also
be considered to simulate the dynamic dilution process of the chemical compositions
of the wire.
In theory, the simulation results of the keyhole and weld pool in the welding
with filler wire in this chapter can provide initial conditions such as composition for
dynamic dilution research. However, because the physical mechanism of the laser
welding with filler wires is very complicated, if the simulation results in this chapter
are used as initial conditions, it will bring great difficulties to the test verification of
the simulation results of the dynamic dilution research. In order to facilitate the test
verification of the established dynamic dilution simulation of the moving weld pool,
an idealized boundary condition is set up and a layer of wire powder is required
to be laid on the surface of the moving weld pool. That is, at these locations, the
concentration values of the chemical compositions of the wire have the following
boundary conditions
C = 1.0
(8.19)
8.5.2 Dynamic Dilution Behavior in Quasi-Steady Weld Pools
As the laser welding process goes on, the moving weld pool will enter a relatively
stable state, and the obtained weld joint tends to be in a relatively stable shape, that is,
the welding process enters the quasi-steady state. After the welding process reaches
the quasi-steady state, on the one hand, the melted wire material will continuously
enter the weld pool from the melting front of the front end of the moving weld
pool; on the other hand, the chemical compositions carried in the wire will gradually
leave the moving weld pool from the solidification front of the moving weld pool.
Therefore, studying the dilution process of the chemical compositions of the wire
in the moving weld pool when the welding process reaches the quasi-steady state
is of great significance to explain the dynamic dilution mechanism of the moving
weld pool in the laser welding process and reveal the distribution law of the chemical
compositions of wire inside the weld joint.
8.5.2.1 Calculation for Quasi-Steady Moving Weld Pools
By solving the transient coupling model of laser welding and laser welding with filler
wires, important information such as the three-dimensional morphology, temperature
field, flow field and keyhole morphology of the quasi-steady moving weld pool during