Chapter 8
Keyhole and Weld Pool Dynamics
in Laser Welding with Filler Wires
Abstract This chapter introduces the time-dependent keyhole and weld pool
dynamics in laser welding with filler wires. Mathematical models of the welding
process including wire feeding model, boundary conditions, and keyhole and weld
pool coupling model are presented. Keyhole and weld pool behaviors under different
wire transfer modes including droplet and continuous transfer are discussed in detail.
The oscillation mechanisms of keyhole and weld pool in laser welding with filler
wires are investigated. The time dependent dilution behaviors of weld pool by the
filler wire are also studied.
8.1 Introduction
Currently, the common laser welding is basically self-fluxing welding. In self-fluxing
welding, the parent metal is heated and molten under laser action and solidified to
form a weld joint without the use of wire or welding flux. This welding method can
produce excellent weld joints for most materials like steel. Materials like aluminum
alloy and magnesium alloy, however, feature high thermal conductivity, high coefficient of thermal expansion, low surface tension of the weld pool, and volatility of
alloy compositions like Mg, Zn, and Li. When they are subject to laser self-fluxing
welding, evaporation of alloy composition with low-boiling point will degrade the
property of a weld joint and cause cracks, pores, poor welding formation, and other
defects. Moreover, many high-strength aluminum alloys have bad weldability. As
laser self-fluxing welding does not need additional materials, the chemical compositions of the weld pool and weld joint metal are hard to control. As a result, it is
difficult to form a satisfactory weld joint. In addition, the self-fluxing welding beam
of the ordinary laser is extremely small in diameter, setting high requirements on
gap joints and welding centering (allowance <0.1 mm generally). These factors have
restricted the application of laser self-fluxing welding in practice to some extent.
To address the above limitations of the laser self-fluxing welding and better expand
application of the laser welding, the technique of laser welding with filler wires is
developed based on the laser self-fluxing welding. The welding technique is similar
to MIG welding in principle; the wire feeder is used to drive the wire to enter the
© China Aviation Publishing & Media Co., Ltd. 2021
S. Gong et al., Weld Pool Dynamics in Deep Penetration Laser Welding,
https://doi.org/10.1007/978-981-16-0788-2_8
203
Keyhole and Weld Pool Dynamics
in Laser Welding with Filler Wires
Abstract This chapter introduces the time-dependent keyhole and weld pool
dynamics in laser welding with filler wires. Mathematical models of the welding
process including wire feeding model, boundary conditions, and keyhole and weld
pool coupling model are presented. Keyhole and weld pool behaviors under different
wire transfer modes including droplet and continuous transfer are discussed in detail.
The oscillation mechanisms of keyhole and weld pool in laser welding with filler
wires are investigated. The time dependent dilution behaviors of weld pool by the
filler wire are also studied.
8.1 Introduction
Currently, the common laser welding is basically self-fluxing welding. In self-fluxing
welding, the parent metal is heated and molten under laser action and solidified to
form a weld joint without the use of wire or welding flux. This welding method can
produce excellent weld joints for most materials like steel. Materials like aluminum
alloy and magnesium alloy, however, feature high thermal conductivity, high coefficient of thermal expansion, low surface tension of the weld pool, and volatility of
alloy compositions like Mg, Zn, and Li. When they are subject to laser self-fluxing
welding, evaporation of alloy composition with low-boiling point will degrade the
property of a weld joint and cause cracks, pores, poor welding formation, and other
defects. Moreover, many high-strength aluminum alloys have bad weldability. As
laser self-fluxing welding does not need additional materials, the chemical compositions of the weld pool and weld joint metal are hard to control. As a result, it is
difficult to form a satisfactory weld joint. In addition, the self-fluxing welding beam
of the ordinary laser is extremely small in diameter, setting high requirements on
gap joints and welding centering (allowance <0.1 mm generally). These factors have
restricted the application of laser self-fluxing welding in practice to some extent.
To address the above limitations of the laser self-fluxing welding and better expand
application of the laser welding, the technique of laser welding with filler wires is
developed based on the laser self-fluxing welding. The welding technique is similar
to MIG welding in principle; the wire feeder is used to drive the wire to enter the
© China Aviation Publishing & Media Co., Ltd. 2021
S. Gong et al., Weld Pool Dynamics in Deep Penetration Laser Welding,
https://doi.org/10.1007/978-981-16-0788-2_8
203