What Is Laser Welding and How Does it Work?

I. Core Technical Support for Precision Manufacturing

Laser welding is a key technology in modern industrial precision manufacturing. It is widely applied in key industries such as aerospace, automotive manufacturing, electronic information, and medical devices, playing a crucial role in driving the high-quality development of various fields.

Aerospace Industry: Used for welding key components of aircraft engines, ensuring the connection strength and stability of components under high-temperature, high-pressure, and high-speed operating conditions;

Automotive Manufacturing Industry: Applied in the welding of vehicle body frames and battery modules of new energy vehicles, improving body safety and battery energy density.

Electronics Industry: Enables precision connection of micro-components such as mobile phone camera modules and chip packaging, meeting the miniaturization needs of electronic products.

Medical Industry: Used in the manufacturing of implantable devices such as pacemakers and artificial joints, ensuring the biocompatibility of devices with their small heat-affected zone.

II. Core Advantages of Laser Welding

Compared with traditional welding methods, laser welding has significant technical advantages:

High Precision: With highly concentrated energy, it can achieve micron-level welding, meeting the processing requirements of precision components.

Small Heat-Affected Zone: Local high-temperature action has minimal impact on the performance of surrounding materials, greatly reducing material deformation.

Excellent Efficiency: Fast welding speed, suitable for mass production scenarios, improving manufacturing efficiency.

Wide Adaptability: Capable of welding various materials such as metals, plastics, and glass, breaking the material limitations of traditional welding.

III. Working Principle of Laser Welding

(I) Laser Generation Mechanism

Lasers generate lasers: The working medium (such as semiconductors and crystals) is excited by electrical or optical energy, causing electron transitions in atoms to form population inversion; Photons generated by stimulated emission are amplified through a resonant cavity, and finally, a laser beam with high brightness, high directionality, monochromaticity, and coherence is output.

(II) Energy Conversion Process of Welding

When the laser beam acts on the material surface, energy is quickly absorbed and converted into thermal energy, raising the material temperature above the melting point to form a molten pool; As the laser beam moves, the liquid metal at the tail of the molten pool cools and solidifies, forming a strong metallurgical bond to complete the welding.

(III) Popular Analogy for Energy Focusing

Similar to how a magnifying glass focuses sunlight to heat and burn a piece of paper, a laser is focused on a tiny area of the material (with a diameter ranging from microns to millimeters) through a high-precision optical system, forming a high power density of millions of watts per square centimeter, and quickly realizing the melting or vaporization of the material.

IV. Two Core Welding Processes

(I) Conduction Welding

Principle: Laser energy diffuses into the material through heat conduction, and the metal only melts to a liquid state (without vaporization), with uniform heat transfer direction;

Characteristics: Slow welding speed, but no spatter, low smoke, and high welding quality. Suitable for scenarios with strict quality requirements such as precision electronics and medical devices.

(II) Keyhole Welding

Principle: The high-energy-density laser vaporizes the metal, forming a "keyhole" filled with vapor. The laser beam penetrates into the material through the keyhole for heating, and heat transfer is mainly perpendicular to the laser beam;

Characteristics: Fast welding speed, suitable for high-yield production lines (such as automotive body welding), but prone to porosity and a large heat-affected zone (HAZ).

V. Wide Material Adaptability

(I) Metal Materials

It can weld aluminum and aluminum alloys (overcoming the problems of high thermal conductivity and oxide films), copper and copper alloys (solving the problem of high reflectivity), and stainless steel (achieving high-precision and low-deformation welding), meeting the connection needs of metal components in various industries.

(II) Non-Traditional Materials

Thermoplastics: Seamless connection is achieved through laser transmission welding, and the weld strength can reach the level of the base material;

Glass: Vacuum laser welding technology is used to avoid oxidation, suitable for the manufacturing of touch screens and vehicle windows;

Carbon Fiber Composites: The welding process does not damage the material structure, maintaining high strength and low density characteristics. Suitable for aerospace and high-end sports equipment.

VI. Challenges and Countermeasures for Dissimilar Metal Welding

(I) Main Challenges

Due to differences in melting points, light absorption rates, and heat conduction rates, dissimilar metals are prone to problems such as unstable weld mechanical properties, poor weld formation, and the generation of intermetallic compounds.

(II) Solutions

Laser Brazing: Low-melting-point brazing filler metal is used. The laser heats the brazing filler metal to a molten state (the base material does not melt), and fills the gap through capillary action to enhance the joint strength;

Laser Oscillation Welding: The laser beam oscillates according to a specific trajectory (circular, figure-of-eight, etc.), promoting the uniform fusion of metals, eliminating gas to reduce porosity, and improving joint quality.

VII. Innovative Methods to Reduce Spatter

(I) Principle of Adjustable Ring Mode

Through a special optical design, an annular preheating area is formed around the laser spot, making the workpiece heated gently, reducing the fluctuation of the molten pool, and fundamentally reducing the generation of spatter.

(II) Key Equipment Requirements

A fiber optic cable with an outer core is required: The inner core transmits the main laser beam, and the outer core transmits the annular beam. Through precise control of beam parameters, the fine distribution of energy is achieved.

VIII. Future Development Outlook

Laser welding will develop towards higher power (processing thick and refractory materials), more precise control (real-time monitoring and regulation), and multi-technology integration (combining AI and robot technology to achieve automation and intelligence). It will further expand its application in fields such as new energy batteries, aerospace precision components, and microelectronic components, promoting the upgrading of the manufacturing industry towards higher quality and higher efficiency.