Chapter 9
Dynamical Behaviors of Keyhole
and Weld Pool in Vacuum Laser Welding
Abstract This chapter introduces the dynamics behaviors of keyhole and weld pool
in vacuum laser welding. Mathematical model for simulating time dependent keyhole
and weld pool dynamics in vacuum laser welding is given. The physical behaviors of
keyhole dynamics and flow pattern of weld pool under vacuum welding are discussed.
The mechanisms of penetration increase under vacuum conditions are explained
using numerical simulations.
9.1 Introduction
Vacuum laser welding refers to the welding of workpieces in a vacuum or low vacuum
environment by using laser energy. This welding method produces a penetration
depth comparable to that in vacuum electron beam welding, and delivers excellent
welding quality without radiation pollution. It is perfectly suitable for thick plates.
Recent years have seen revolutionary breakthroughs in fiber laser technology. The
power of industrial fiber lasers which can work stably for a long term has reached
100 kW. Vacuum laser welding is able to penetrate thick-walled components to a
depth of more than 100 mm at a time. It offers a wide range of potential applications
in space vehicles, deep-sea equipment, and other fields, and is an important joining
technology for the key equipment in the national major strategic engineering projects,
such as space engineering and deep ocean engineering.
Similar to laser welding under atmospheric conditions, vacuum laser welding is
characterized by rapid gasification and liquefaction of workpieces under a laser beam
to form a weld pool, a keyhole, and metallic vapors. However, performed in a vacuum
and low vacuum environment, the latter significantly differs from the former in the
dynamic characteristics of keyhole and weld pool and the profile and quality of welds.
Unlike electron beam which is sensitive to air pollution and requires high degrees
of vacuum, laser beam allows high-quality welding under atmospheric conditions
by using appropriate welding parameters. In industrial applications, laser welding
under vacuum is favored mainly for its ability of achieving a penetration depth several
times the depth obtained under atmospheric conditions. Understanding how vacuum
degree (ambient pressure) influences penetration depths in laser welding can help
© 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_9
253
Dynamical Behaviors of Keyhole
and Weld Pool in Vacuum Laser Welding
Abstract This chapter introduces the dynamics behaviors of keyhole and weld pool
in vacuum laser welding. Mathematical model for simulating time dependent keyhole
and weld pool dynamics in vacuum laser welding is given. The physical behaviors of
keyhole dynamics and flow pattern of weld pool under vacuum welding are discussed.
The mechanisms of penetration increase under vacuum conditions are explained
using numerical simulations.
9.1 Introduction
Vacuum laser welding refers to the welding of workpieces in a vacuum or low vacuum
environment by using laser energy. This welding method produces a penetration
depth comparable to that in vacuum electron beam welding, and delivers excellent
welding quality without radiation pollution. It is perfectly suitable for thick plates.
Recent years have seen revolutionary breakthroughs in fiber laser technology. The
power of industrial fiber lasers which can work stably for a long term has reached
100 kW. Vacuum laser welding is able to penetrate thick-walled components to a
depth of more than 100 mm at a time. It offers a wide range of potential applications
in space vehicles, deep-sea equipment, and other fields, and is an important joining
technology for the key equipment in the national major strategic engineering projects,
such as space engineering and deep ocean engineering.
Similar to laser welding under atmospheric conditions, vacuum laser welding is
characterized by rapid gasification and liquefaction of workpieces under a laser beam
to form a weld pool, a keyhole, and metallic vapors. However, performed in a vacuum
and low vacuum environment, the latter significantly differs from the former in the
dynamic characteristics of keyhole and weld pool and the profile and quality of welds.
Unlike electron beam which is sensitive to air pollution and requires high degrees
of vacuum, laser beam allows high-quality welding under atmospheric conditions
by using appropriate welding parameters. In industrial applications, laser welding
under vacuum is favored mainly for its ability of achieving a penetration depth several
times the depth obtained under atmospheric conditions. Understanding how vacuum
degree (ambient pressure) influences penetration depths in laser welding can help
© 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_9
253