Challenges in Laser Welding Technology for Red Copper Applications

In the industrial manufacturing sector, copper ranks second in consumption among non-ferrous metals, trailing only aluminum. Copper finds extensive applications across industries such as construction, electrical engineering, and machinery manufacturing. It possesses excellent electrical and thermal conductivity, superior plasticity, and is easily processed through both hot and cold forming. As production demands continue to evolve, the applications of copper have gradually expanded.

Laser welding offers advantages such as high energy density, minimal metal consumption, narrow heat-affected zones, superior weld quality, and enhanced production efficiency. Its capability for copper welding has led to increasing adoption across various industries. However, due to copper's high absorption rate for fiber lasers, processing challenges impose stricter requirements on the laser source.

Copper welding commonly presents the following challenges:

(1) Difficulty in fusion and variability: Copper's high thermal conductivity causes rapid heat transfer during welding, resulting in a narrow heat-affected zone across all welded areas. This makes achieving uniform fusion challenging. Additionally, copper's high coefficient of linear expansion can lead to deformation if clamping force is improperly applied during heating.

(2) Prone to porosity: Another significant issue in copper welding is porosity, particularly severe during deep penetration welding. Porosity primarily arises from two mechanisms: dispersion porosity caused by hydrogen dissolution in copper, and reaction porosity resulting from redox reactions.

Solutions:

Copper exhibits approximately 5% absorption of infrared laser energy at room temperature, increasing to around 20% near its melting point. To achieve deep laser penetration welding of copper, high laser power density is required.

During deep penetration welding, a high-power laser oscillates the weld joint, agitating the molten pool with the laser beam to enlarge the hole. This facilitates gas escape, stabilizes the welding process, and reduces post-weld spatter and porosity.

Welding Techniques:

(1) During welding, the joint angle should be inclined to prevent prolonged laser reflection damage.

(2) Laser power must reach copper's absorption threshold to prevent light reflection.

(3) Copper's absorption threshold is easily achieved using a small core diameter with high energy density.

(4) Oscillating welding ensures superior surface quality.