Laser Beam Welding Explained: How It Transforms High-Precision Welds

Picture of laser beam welding. Photo courtesy of LaserTherm // Wikimedia Commons.

Like many aspects of modern life, welding has seen rapid advancements in recent years. One area leading this charge is laser welding—a process that brings unmatched precision and versatility to the trade.

What Is Laser Beam Welding?

Laser Beam Welding (LBW) is a cutting-edge welding process that uses a concentrated light beam to melt and fuse metals with precision. Known for its accuracy and minimal heat distortion, it's perfect for jobs that need speed and flawless results.

The word “laser” is an acronym meaning “light amplification by stimulated emission of radiation.”

A laser is a highly concentrated beam of light generated by an external energy source that excites atoms in a solid, liquid, or gas medium. Stimulated emission happens when there are more atoms in an excited state than in a low-energy state. This process is triggered when a photon excites an atom, prompting it to release energy. The atom then emits a second photon of the same wavelength traveling in the same direction, resulting in a chain reaction. The medium in this excited state is then placed between two mirrors, which form an optical cavity that reflects and amplifies the light. This is allowed to escape through a partially reflective mirror, forming a single, highly focused beam.

Laser welding's main appeal is its accuracy—small diameter beams are great for cutting, while wider beams are ideal for heating and welding. This control makes it the go-to process for certain applications requiring top-notch quality.

Types of Lasers Used in Welding

Many types of lasers are used in laser welding. Each has unique characteristics that make it well-suited to specific applications. Lasers used for welding generally fall into one of two categories: gas lasers and solid-state lasers.

Gas Lasers

Gas lasers are often used in sheet metal applications with CO2 (or sometimes helium or nitrogen) as the medium.

Nd:YAG (Neodymium-doped Yttrium, Aluminum and Garnet) Lasers

A type of solid-state laser, Nd:YAG lasers use ores such as yttrium, aluminum, or garnet as their medium.

Fiber Lasers

Fiber lasers are precise and highly efficient. They are one of the most common options for welding, due to their high welding speeds and low maintenance needs.

Disk Lasers

In disc lasers, the beam is filtered through a disc or series of discs to create a highly concentrated laser beam with a small diameter.

How Laser Beam Welding Works

In laser welding, the laser beam moves over the weld joint, either manually or in an automated process. The intense heat generated by the laser beam is focused on the surfaces in the weld joint. The heat that the laser beam creates melts the metals in the joint. When the laser beam moves past, the molten weld pool solidifies, which forms the welded joint.

Equipment and Setup

Laser welding requires a few essential components:

Laser Source

The main component in a laser welding operation is the laser source. The power of the laser must match the material and job requirements, depending on several factors, including material thickness, type, and reflectivity.

Optics and Beam Delivery

The optical system primarily consists of a focusing lens, used to produce a highly-concentrated beam with a specific diameter. This increases the intensity of the beam on the workpiece.

The beam delivery system is composed of either fiber optics or mirrors, which direct the laser beam from the source to the work area as efficiently as possible to minimize the loss of energy.

Workpiece and Fixtures

An essential component of any welding setup, a workbench (complete with the standard complement of clamps and fixtures) is necessary to hold the pieces firmly in place. It also needs adequate spacing and alignment for the welding operation.

Safety Precautions

As with any welding process, there are some inherent hazards to laser welding that welders must understand and address before beginning any welding operations.

PPE

One of the most important pieces of personal protective equipment is laser safety goggles rated to the specific wavelengths of the laser. Lasers are sometimes so powerful and highly concentrated that immediate and irreparable damage could occur if the laser beam were to make direct contact with the eye!

There is also a risk of light reflecting off the workpiece or even the walls in the welding area if they are flat, bright, and reflective.

Additionally, welders should wear gloves and long-sleeve, fire-resistant shirts or a welding jacket to protect against the heat of the laser beam.

Ventilation and Fume Extraction

Although laser welding is a “cleaner” process than some of the more traditional welding techniques (like stick or flux-core welding, for example), heating metals to their melting point may emit fumes that can be harmful to respiratory health. It’s important to always work in a well-ventilated area.

Fire Prevention

Laser welding typically produces few (if any) sparks, but accidents may happen whenever metal is heated to its melting point. Keep the welding area free from combustible materials and always have a fire extinguisher on hand in case of emergencies.

Storing Materials

Store laser welding materials in a clean, dry environment, preferably on an elevated surface to avoid moisture exposure, as moisture may result in oxidation and lead to contamination in the welding operations.

Laser Beam Welding Techniques

There are three main ways to perform laser welding: conduction welding, keyhole welding, and transition welding. The more suitable type will depend on the mode of transfer and the penetration depth required.

Conduction Welding

With conduction welding, the laser heats the surface of the metal, causing it to melt and fuse as the welding progresses down the weld joint in the workpiece. This method is typically used for thinner metals because it does not penetrate deeply into the base metal, which results in a shallow weld pool.

This method joins thin sections of material or small components, where minimizing the heat-affected zone is important to prevent distortion or warping in the workpiece.

Keyhole Welding

The keyhole welding method creates a narrow but deep penetrating weld. The laser energy is so highly concentrated that it vaporizes the material at the bottom of the weld puddle, which creates a cavity that allows molten metal to flow in.

This method is ideal for joining thick sections of material and for applications where strong welds are necessary.

Transition Welding (Conduction/Keyhole)

For materials that fall in between, there’s a transition welding method that blends the benefits of both conduction and keyhole welding. It starts with a shallow, conduction-style weld but transitions to deeper penetration when necessary. This method is a great option when you need a balance between heat input and penetration depth for more versatile applications.

Settings That Impact Laser Beam Welding

Laser beam welding is all about precision, and getting the settings right makes all the difference. From power levels to focal position, each setting impacts the quality and efficiency of your welds.

Laser Power

The power of the laser (measured in watts) affects penetration and the speed at which the welding can take place. Higher power increases weld penetration and travel speed. However, too much power and speed may lead to excessive heat in the weld joint, which may cause excessive melting of the base metal, warping, and distortion.

Welding Speed

The formula for determining heat input is amperage x volts x 60 / travel speed (inches per minute). This formula shows that travel speed is the biggest single determining factor in controlling the heat input to the weld joint. A faster travel speed may result in insufficient penetration, whereas a slower travel speed may lead to excessive heat input, which may result in warping and distortion in the base metal.

Focal Position

The focus and spot size determine the density of the energy in the weld joint. A smaller spot size or focal point increases energy density, which leads to deeper penetration.

Shielding Gas

Shielding gas in the welding process protects the molten weld puddle from atmospheric contamination. Oxygen and nitrogen in the weld puddle will almost always result in the formation of gas pockets in the weld when it solidifies, resulting in a weld defect known as porosity. The right shielding gas for the base metal and type of laser will protect the molten weld puddle from contamination and is a critical factor in ensuring weld quality.

Uses of Laser Beam Welding

Various industrial processes use laser beam welding, due to its speed, precision, and capability to produce clean, consistent, high-quality welds on several different alloys.

Automotive Industry

Laser beam welding has long had automotive applications, due to its precision and versatility to make high-quality welds on different alloys with high productivity and consistent quality.

Aerospace Industry

Laser beam welding has long been a mainstay in the aerospace industry due to its capability to weld various materials. The aerospace industry is notorious for its demand for high-quality precision welds on a variety of exotic alloys, all of which laser beam welding can weld.

Electronics and Microelectronics

The electronics sector also uses laser beam welding. The high precision and high-speed capabilities make it possible to join small parts in devices like computers and servers with low heat input.

Medical Device Manufacturing

Laser beam welding is common in the fabrication of delicate surgical instruments, where precision and cleanliness are important.

Energy Sector

The energy sector often uses laser beam welding in the fabrication and repair of small pipe sections that require strong, durable weld joints for containment under pressure and structural rigidity.

Advantages of Laser Beam Welding

There are some key advantages to using laser welding.

High Precision

The highly focused laser beam means laser welding can join very small parts with intricate weld joints. Laser welding is common for welding small parts that require higher degrees of precision than would be attainable with many traditional welding processes.

Minimal Distortion and Heat-Affected Zones

It is possible to perform laser welding at very high speeds, which results in a low heat input into the base metals. Lower heat inputs mean less warping and distortion in the workpiece.

High Welding Speeds

Welding with laser beams uses such a highly focused beam in such a small area that it generates high temperatures in a short amount of time. This facilitates the quick melting of the base metal in the weld joint, which leads to higher welding speeds.

Versatility

Laser welding offers a high degree of versatility in several respects:

The capability to weld dissimilar metals, which is often difficult (if not impossible) with more traditional welding processes.
Incorporation into various automation systems, which enhances efficiency and production.
Suitability for a wide variety of metals and alloys, like stainless steel, titanium, aluminum, copper, brass, and bronze.
Suitability for both thick and thin metals. In thick sections of metal, the laser beam can penetrate deeply into a base metal without the need for excessive joint preparation, which would be necessary with other welding processes.
Suitability for intricate designs with tight tolerances. The high precision makes laser welding well-suited to applications like creating electronic components, aerospace structures, and medical devices that need high-quality welds.

Challenges and Limitations of Laser Beam Welding

Just like with every welding process, laser beam welding does have limitations that welders should consider before choosing this technique.

Costs

One of the biggest drawbacks is the high cost, which may make laser welding cost-prohibitive for small shops and home hobbyists.

Initial Investment

The cost of a laser welding setup varies significantly, with prices ranging from $25,000 to over $150,000. Some automated industrial systems may cost substantially more.

Maintenance Costs

Laser welding equipment requires regular maintenance to ensure optimal performance. It’s necessary to clean the internal components, calibrate the laser optics, check alignment, and replace worn-out or damaged components regularly.

Laser welding systems often utilize cooling systems to prevent overheating. The coolant may need changing at regular intervals. Plus, the hoses and related fittings are subject to wear and tear with repeated use.

The laser welding system may require various consumable items, such as lenses and mirrors. The gas will also need replacing regularly.

Operational Costs

There are significant expenses related to operating a laser welding system. Laser welding may consume a lot of electricity — the exact amount will depend on the type of laser welding, type of material, and material thickness.

Skill Requirements

Laser welding is quick and easy to learn. More than anything, making quality welds requires knowing how to set up and operate the laser welding equipment. Welders need to receive training to be able to set up the equipment, operate it safely, and perform maintenance and troubleshooting in the event of a malfunction.

Penetration Depth

Materials react differently to laser welding. Characteristics such as reflectivity, thermal conductivity, and melting point have a significant impact on the depth of weld penetration.

To achieve the proper weld depth, it is important to understand the welding parameters, such as power, travel speed, and focus.

Excessive heat generated by high power may result in excessive heat input. Since this may lead to distortion in the workpiece, it’s important to pay attention to the joint configuration.

Any inconsistency in the fit-up of the weld joint may lead to inconsistency in joint penetration, which may lead to weld defects. It is important to make sure the weld joint is fitted up properly and consistently along the entirety of the weld joint.

Future of Laser Beam Welding

Laser beam welding is poised for even further technological advancements in the coming years. The following are some key trends that may drive further development of technological advances in the area of laser beam welding.

Advances in Laser Technology

Advances within laser technology itself — like more high-powered lasers and disk and fiber lasers — will enable faster welding speeds with deeper penetration, which will lead to deeper-penetrating welds on thicker materials.

Automation and Robotics

It will likely be possible to integrate laser beam welding with robotics welding technology, which will enhance both welding productivity and weld consistency, leading to lower production costs. This may be one way to counter the shortage of skilled welders in the marketplace.

Monitoring and Quality Control

Ongoing research in laser technologies will enhance laser characteristics, improving welding productivity and quality while paving the way for new applications.

FAQs

What is laser beam welding, and how does it differ from traditional welding methods?

In laser beam welding heat is not generated through an electric arc produced by a circuit but by a highly concentrated beam of light. This is precise enough to melt and fuse the base metal.

What are the advantages of using laser beam welding in industrial applications?

Laser beam welding can produce deep penetration welds with a high degree of precision at high welding speeds. This might be difficult to replicate with traditional welding processes.

What safety precautions are essential when using laser beam welding equipment?

Laser beam welding requires special safety glasses or goggles. Not only is the laser inherently dangerous if it comes into contact with the eye, but light reflecting off the workpiece (especially when the workpiece is stainless steel or another highly reflective alloy) may also pose a risk to the eyes. Always use glasses and goggles designed for laser welding.

Featured photo courtesy of TRUMPF GmbH + Co. KG // Wikimedia Commons