What Is Laser Beam Welding ?

Laser Beam Welding

Laser beam welding (LBW) is a welding process that uses a laser beam to join materials. It is a high-energy-density welding technique that can produce precise and efficient welds.

What Is Laser Beam Welding

Laser beam welding (LBW) is a modern welding technique that uses a highly focused laser beam to join materials together. It is a high-energy-density welding process that can produce precise and efficient welds. The key components of laser beam welding include the laser source, optics for beam delivery and focusing, and a workpiece.

Laser beam welding is primarily used for its high welding speeds, small seams, and relatively low amount of unwanted thermal distortion to the final product. Add in automated operation and the capacity to control a laser over an internet connection, and it’s easy to see why laser welding has become a standard process in industrial fabrication today.

Laser welding has two fundamental modes; conduction-limited welding and keyhole welding, with mode depending largely on the power density across the laser beam.

Performed at lower power densities, conduction-limited welding involves the laser beam energy being absorbed solely at the target materials’ exterior. This mode produces welds with a high width-to-depth ratio.

Typically done at greater power densities, keyhole welding involves concentrating a laser beam on a spot small enough to cause the materials at the target spot to melt, and then vaporize. The energy of the focused laser beam penetrates deep into the work surface(s), creating a cavity known as a ‘keyhole’ that is subsequently filled with metal vapor. In some cases, this vapor can ionize to create a plasma. This vapor (or plasma) expands and, in doing so, prevents the collapse of the keyhole’s molten walls.

A deep weld can then be created by passing the keyhole-forming laser beam down the gap meant to be fused. Due to surface tension, some molten source material at the keyhole’s front edge flows around the back of the cavity, where it cools and solidifies. This creates a weld cap with a chevron design that points towards the origin point of the process. This mode results on welds with a high depth-to-width ratio.

As with any fusion welding process, laser beam welding can contain defects, especially when done with steel. Without suitable preparation of source materials and the right welding parameters, some defects become more likely such as cracks, pores and general weakness.

The welding speed and weld shape are also critical factors. High welding speeds tend to create deep, narrow welds, with a single central boundary, while lower speeds lead to a broader, shallower weld, which may have a stronger, intricate solidification structure in place. The weld shape can be affected by raising heat and/or using a laser beam with a bigger focus diameter, both of which can broaden the weld.

How Does Laser Beam Welding Work

Generation of Laser Beam: The process begins with the generation of a highly focused and intense laser beam. The most common types of lasers used in laser welding are solid-state lasers, fiber lasers, and CO2 lasers.
Focusing the Laser Beam: The laser beam is then focused on the workpiece through a lens or a set of mirrors. The focusing optics concentrate the laser energy into a small, well-defined spot.
Material Interaction: The focused laser beam rapidly heats and melts the material at the point of interaction. The intense heat causes the material to undergo a phase change from solid to liquid, forming a weld pool.
Weld Pool Formation: The molten material in the weld pool solidifies as the laser beam moves along the joint. The solidification process creates a strong and durable weld joint.

Laser Beam Welding Process

Preparation of Workpiece: Before welding, the workpiece surfaces to be joined are prepared. This may involve cleaning, polishing, or applying a coating to enhance absorption of the laser energy.
Fixturing and Clamping: The workpieces are securely fixtured and clamped in position to ensure proper alignment during the welding process. This is particularly important for achieving precise and accurate welds.
Initiation of Laser Welding: The laser beam is directed to the starting point of the weld joint. The beam is then turned on, and the welding process begins. The laser energy rapidly heats and melts the material at the interaction point.
Weld Pool Formation: As the material absorbs the laser energy, it transforms into a molten state, forming a weld pool. The size and shape of the weld pool depend on factors such as laser power, travel speed, and material properties.
Beam Movement: The laser beam is moved along the joint line at a controlled speed. This movement allows the molten material to solidify, creating a continuous welded seam.
Solidification: As the laser beam progresses, the molten material solidifies, creating a strong and durable weld joint. The rapid solidification characteristic of laser welding helps minimize the heat-affected zone. Cooling and Post-Weld Treatment: After the welding is complete, the welded joint undergoes a cooling process.
Depending on the material and application, additional post-weld treatments such as stress relieving or surface finishing may be performed.
Quality Inspection: The final welded joint is inspected for quality, including factors like weld penetration, width, and absence of defects.
Non-destructive testing methods may be employed to ensure the integrity of the weld.

Advantages of Laser Beam Welding

Precision: Laser welding can achieve high levels of precision and accuracy, making it suitable for delicate and intricate work.
Speed: The process is often faster than traditional welding methods.
Heat Control: Laser welding minimizes the heat-affected zone, reducing the risk of distortion and damage to the surrounding material.
Automation: Laser welding can be easily automated for high-volume production.

Application of Laser Beam Welding

Welding Applications: Laser beam welding is used for joining a wide range of materials, including metals and alloys such as stainless steel, aluminum, titanium, and various steels. It is suitable for both thin and thick materials and can be used for spot welding, seam welding, butt welding, and other joint configurations.

Laser beam welding is known for its precision, speed, and ability to produce high-quality welds in a variety of materials. It is used in various industries, including automotive, aerospace, electronics, and medical device manufacturing. The process is particularly well-suited for applications that require fine detail, minimal distortion, and a reduced heat-affected zone.