Key Characteristics of Laser Welding in Modern Metalworking

Main Characteristics of Laser Welding

Laser welding is an efficient and precise welding method that utilizes a high-energy-density laser beam as a heat source. When employing laser welding, not only is the production rate higher than traditional welding methods, but the welding quality is also significantly improved.

Main Characteristics of Laser Welding

In comparison to general welding methods, laser welding possesses the following characteristics:

1) The power density after focusing can reach 105 to 1010 W/cm2, or even higher. The concentrated heating results in low heat input required to complete the welding of a unit length or unit thickness of the workpiece, thereby minimizing deformation and creating a narrow heat-affected zone. This makes it particularly suitable for precision and micro welding.

2) Laser energy can be emitted and transmitted with minimal attenuation over considerable distances in space, enabling welding in remote locations or areas that are difficult to access. The laser can be transmitted, bent, redirected, and focused through optical methods such as optical fibers and prisms, making it especially suitable for welding micro parts, inaccessible areas, or long-distance welding.

3) It can achieve a high depth-to-width ratio for the weld seam, allowing for welding thick sections without the need for beveling in a single pass. The depth-to-width ratio of laser welds has reached 12:1, and single-pass welding of steel plates without beveling has reached a thickness of 50 mm.

4) A single laser can be used for multiple workstations to perform various tasks, including welding, cutting, alloying, and heat treatment, achieving multi-functionality.

5) Suitable for welding refractory metals, highly thermally sensitive metals, as well as workpieces with significant differences in thermal and physical properties, sizes, and volumes. It has a wide range of weldable material types and can join various dissimilar materials.

6) Capable of welding workpieces inside sealed containers by penetrating transparent media.

7) The laser beam is not affected by electromagnetic interference, and there is no magnetic deviation phenomenon, making it suitable for welding magnetic materials.

8) It does not require a vacuum chamber, does not produce X-rays, and is convenient for observation and alignment.

Main Drawbacks of Laser Welding

1) The positioning of the workpiece needs to be extremely precise and must be within the focusing range of the laser beam.

2) When using fixtures for the workpiece, it is essential to ensure that the final position of the workpiece aligns with the points where the laser beam will impact.

3) The maximum weldable thickness is limited by the penetration depth, and for workpieces with a penetration depth far exceeding 19mm, laser welding is not suitable for use on the production line.

4) Materials with high reflectivity and high thermal conductivity, such as aluminum, copper, and their alloys, are significantly affected by the wavelength of the laser and are challenging to weld using heat conduction welding.

5) When using medium to high-energy laser beam welding, a plasma controller is required to expel ionized gas around the molten pool to ensure the stability of the welding process. For CO2 deep penetration welding, inert gas is used to blow away the plasma above the molten pool to eliminate its absorption and shielding of the laser, ensuring a stable welding process.

6) The energy conversion efficiency of CO2 laser is relatively low, currently only reaching 30% to 40%.

7) Rapid solidification of the weld may lead to the risk of porosity and embrittlement.

8) The equipment is expensive.

To eliminate or reduce the drawbacks of laser welding and better utilize this advanced welding method, engineering often adopts processes that combine laser with other heat sources, including laser-arc, laser-plasma arc, laser-induction heat source composite welding, dual laser beam welding, and multi-beam laser welding.

In addition, various auxiliary process measures such as laser cladding (which can be further divided into cold wire cladding and hot wire cladding), externally applied magnetic field-assisted laser welding, laser-assisted stir friction welding, and laser-assisted deep pool control welding are also employed.

Process Comparison of Laser Welding with Other Welding Methods

The process comparison of laser welding with other welding methods is shown in Table 2-1.

Table 2-1: Process Comparison of Laser Welding and Other Welding Methods

Comparison of ProjectsLaser weldingElectron beam weldingTungsten inert gas (TIG) weldingMetal inert gas (MIG) weldingResistance welding
Welding Efficiency00+
High Depth Ratio++
Small Heat Affected Zone++0
High Welding Speed+++
Weld Bead Cross-Section Appearance++000
Welding Under Atmospheric Pressure+++
Welding High Reflectivity Materials++++
Use of Filler Materials00++
Automated Processing+++0+
Operating Costs00+++
Note: “+” indicates an advantage; “-” indicates a disadvantage; “0” indicates neutral.

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