The Unique Advantages of Laser Welding Technology
1. Laser Welding Technology
Working Principle: Laser-active media (such as a mixture of CO₂ and other gases, YAG yttrium aluminum garnet crystals, etc.) are excited in a specific way to oscillate back and forth within a resonant cavity, generating a stimulated radiation beam. When the beam contacts the workpiece, its energy is absorbed. Welding can be performed once the temperature reaches the melting point of the material.
2. Key Parameters of Laser Welding Technology
(1) Power Density
At low power density, the surface layer takes several milliseconds to reach the boiling point. Before surface vaporization occurs, the underlying layer melts first, facilitating the formation of high-quality fusion welds.
(2) Laser Pulse Waveform
The reflectivity of metals changes dynamically during a laser pulse cycle. It drops sharply once the surface temperature reaches the melting point and stabilizes at a constant value when the surface is in a molten state.
(3) Laser Pulse Width
However, prolonged pulse width reduces peak power. Therefore, longer pulse widths are typically used in heat conduction welding, producing wide, shallow weld seams that are especially suitable for lap welding of thin and thick plates.
That said, low peak power can result in excessive heat input. Each material has an optimal pulse width that maximizes weld penetration.
(4) Defocus Amount
(5) Defocus Modes
According to geometric optics theory, the power density on planes equidistant from the welding surface (in positive and negative defocus configurations) is approximately the same. In practice, however, the resulting weld pool shapes differ slightly. Negative defocus yields greater weld penetration, which is related to the weld pool formation mechanism.
(6) Welding Speed
For a given laser power and specific material thickness, there exists an optimal welding speed range, within which the maximum weld penetration can be achieved at the corresponding speed value.
(7) Shielding Gas
Shielding gas serves three key functions:
- Protect the weld pool from atmospheric contamination.
- Shield the focusing lens from metal vapor contamination and molten droplet spatter—a critical function in high-power laser welding where spatter is highly energetic.
- Effectively disperse the plasma cloud generated during high-power laser welding. Metal vapor absorbs laser energy and ionizes into plasma; excessive plasma can attenuate the laser beam energy.
3. Unique Effects of Laser Welding Technology
- Weld Purification Effect: When the laser beam irradiates the weld seam, oxide impurities in the material absorb laser energy far more efficiently than the base metal. These impurities are rapidly heated, vaporized, and expelled, significantly reducing the impurity content in the weld. Thus, laser welding not only avoids workpiece contamination but also actively purifies the material.
- Photo-Explosion Shock Effect: At extremely high power densities, the intense laser irradiation causes rapid vaporization of metal in the weld seam. Under the pressure of high-velocity metal vapor, molten metal in the weld pool undergoes explosive spattering. The powerful shockwave propagates deep into the material, creating a slender keyhole. As the laser beam moves during welding, surrounding molten metal continuously fills the keyhole and solidifies to form a strong, deep-penetration weld.
- Keyhole Effect in Deep Penetration Welding: When a laser beam with a power density of up to 10⁷ W/cm² irradiates the material, the rate of energy input into the weld far exceeds the rate of heat loss via conduction, convection, and radiation. This causes rapid vaporization of the metal in the laser-irradiated area, forming a keyhole in the weld pool under high-pressure vapor.
Similar to an astronomical black hole, the keyhole absorbs nearly all incident laser energy, allowing the beam to penetrate directly to the keyhole bottom. The depth of the keyhole determines the weld penetration depth.
- Laser Focusing Effect on Keyhole Sidewalls: During keyhole formation in the weld pool, laser beams incident on the keyhole sidewalls typically have a large angle of incidence. These beams reflect off the sidewalls and propagate toward the keyhole bottom, resulting in energy superposition inside the keyhole. This phenomenon, known as the keyhole sidewall focusing effect, effectively enhances the laser intensity within the keyhole and contributes to the unique capabilities of laser welding.
4. Advantages of Laser Welding Technology
- Ultra-Fast Welding Process: The short laser irradiation time enables rapid welding, which not only boosts productivity but also minimizes material oxidation and reduces the heat-affected zone. This makes it ideal for welding heat-sensitive components such as transistors. Laser welding produces no welding slag and eliminates the need for pre-weld oxide removal. It can even perform welding through glass, making it particularly suitable for precision micro-instrument manufacturing.
- Broad Material Compatibility: Laser welding can join not only identical metals but also dissimilar metals, and even metal-nonmetal combinations. For example, integrated circuits with ceramic substrates are difficult to weld using conventional methods due to the high melting point of ceramics and the need to avoid mechanical pressure. Laser welding provides a convenient solution for such applications. Note, however, that laser welding is not suitable for all dissimilar material combinations.
5. Application Scenarios and Industries of Laser Welding
- Heat Conduction Welding: Primarily used for precision machining, such as edge processing of thin metal sheets and medical device manufacturing.
- Deep Penetration Welding & Brazing: Widely adopted in the automotive industry. Deep penetration welding is used for welding car bodies, transmissions, and outer casings; brazing is mainly applied to car body assembly.
- Laser Conduction Welding for Nonmetals: Boasts a wide application range, including consumer goods production, automotive manufacturing, electronic enclosure fabrication, and medical technology.
- Hybrid Welding: Specifically suited for special steel structures, such as ship deck fabrication.
Post time: Dec-15-2025
