Laser Beam Welding Explained | Laserax

Laser beam welding (LBW) is a precise and efficient method used to join materials through the use of a laser beam. It is known for its accuracy, speed, and ability to work on small, delicate components, making it ideal for industries like electronics, batteries, automotive, and aerospace. 

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In this article, we’ll break down how laser welding works, explore its advantages and disadvantages, and clarify the difference between laser beam welding and laser welding.

Table of Contents

• What is Laser Beam Welding?
• How Does Laser Welding Work?
• What are the Advantages and Disadvantages of Laser Welding?
  • Advantages of Laser Welding
  • Disadvantages of Laser Welding
• Which Term is Correct: Laser Welding or Laser Beam Welding?

What is Laser Beam Welding?

Laser beam welding is a precise and highly controlled welding process that uses a concentrated beam of laser light to fuse metals. It can also be used to fuse other materials that can melt and resolidify, such as ceramics and plastics. 

Laser beam welding is ideal for thin or delicate components that require a high level of control and precision. It is used in the battery, automotive, and aerospace industries.

How Does Laser Welding Work?

Laser welding uses the energy contained in a focused beam of light to melt and fuse surfaces.

Here’s how it works step by step:

1. The laser generates a highly focused beam of light using a range of optical and electrical components. You can find an example of how laser beams are generated in fiber lasers here.
2. The laser beam is directed and moved onto the surface using motion axis, robots or fast-rotating mirrors (galvo mirrors).
3. The energy from the laser light is absorbed by the surface. Part of it is also reflected depending on the material’s reflectivity to the selected laser type/wavelenth.
4. The energy absorbed by the surface is converted into heat.
5. The localized surface heats up very quickly, creating a small melt pool. There is minimal heat distortion in surrounding areas.
6. The molten material resolidifies in a few milliseconds, leaving almost no time for contaminants like hydrogen to penetrate the welds.

What are the Advantages and Disadvantages of Laser Welding?

Advantages of Laser Welding

1. Small Heat Affected Zone (HAZ)

The heat-affected zone is the area of the welded piece that has not been melted but that has undergone changes in physical and chemical properties due to high temperatures. 

With laser welding, the heat input is lower because the process is fast and focused. This reduces the size of the heat affected zone and minimizes the potential negative effects on the material’s properties.

2. Good Mechanical Properties

Because laser welding offers better control over the heat input, parts are less distorted and warped by heat. As a result, they maintain better mechanical properties.

3. Ability to Weld Small Components

Laser welding is a precise process that makes use of a highly focused beam of light whose diameter is typically from a few tenths to a few hundred microns. This makes it ideal to weld small components like electronics and battery tabs.

4. Fast Process

Laser welding can be powered by high-power lasers of several thousands of watts. They can be as fast as needed to meet demanding production requirements.

5. Easy to Automate

Modern laser welding systems can operate 24/7 with very little maintenance. This makes them ideal for automated production lines requiring high throughput. They also have access to remote laser heads to perform welding from a distance.

6. High-Quality Welds

Due to the high control over the heat input, laser welded surfaces absorb heat and cool down faster than with traditional methods. This leaves minimal time for contaminants like hydrogen to penetrate the welds and cause mechanical damage.

Disadvantages of Laser Welding

1. Laser Safety Needs to be Ensured

Safety is important with all welding methods. With laser welding, the laser beam and its reflections need to be enclosed.

2. Safety is Complicated with Large Parts 

Larger parts like ships and fuselage sections are complicated to weld safely because larger areas are more difficult to enclose. Engineers often need to come up with new ways to enclose the laser beam.

3. High Initial Investment

Fiber lasers have been getting more affordable each year since , but they are still more expensive than traditional welding technologies.

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4. Reflective Materials

Laser welding works because the surface absorbs energy from the laser beam. With some materials like copper, a large part of certain laser beam is reflected, which makes it challenging for laser experts to optimize the process.

Which Term is Correct: Laser Welding or Laser Beam Welding?

Laser beam welding is the same thing as laser welding. It’s just a fancier term that has stuck for historical reasons. Both terms are correct, but “laser welding” is more common.

Let’s look at the historical context to understand this better.

The Origin of the Words

If you look at the following Ngram, the terms laser welding and laser beam welding both started appearing in the s when there was a lot of interest and research going on in laser welding applications. You can see a trend showing that the term laser welding was already more popular.

The same thing happened with the terms laser cutting and laser beam cutting. Both terms started to be used at the same time, but “laser cutting” has always been more popular.

Dropping the Beam

There’s an interesting shift if you look at other laser processes. No one uses the word “beam” with laser marking, laser cleaning, laser texturing, and many other laser processes.

Why is that?

Laser cutting and laser welding were the first laser processes to be developed. At that time, the technical language was new and still being developed.

As other processes like laser marking and laser cleaning were developed, the word beam was dropped. This shows a general agreement that the word was not needed, or that it didn’t add much clarity or value.

Nowadays

Nowadays, more people use “laser welding” than “laser beam welding”. While “laser beam welding” may still appear in formal contexts, it doesn't make the term more precise or formal. It’s simply an extra word that has persisted for historical reasons.

Laser Welding Machines for Batteries

Laserax manufactures laser welding machines for batteries. These machines are essential to ensure EV battery production keeps up in pace and quality. 

If you want to know how these machines work, watch the following video:

The application of laser in battery welding is a trend in the current market development, and it is determined by the technical advantages of the laser itself. It is one of the important welding technologies that will replace traditional welding in the future.
1. The advantages of laser welding for batteries are mainly reflected in the following points:
1. Energy concentration, high welding efficiency, high processing accuracy, and large weld depth-to-width ratio. The laser beam is easy to focus, align, and guided by optical instruments, and can be placed at an appropriate distance from the workpiece. It can also be guided around the fixtures or obstacles surrounding the workpiece, while other welding methods cannot perform due to the spatial limitations mentioned above.
2. Small heat input, small heat-affected zone, and low residual stress and deformation of the workpiece; welding energy can be precisely controlled, resulting in stable welding effects and good welding appearance.
3. Non-contact welding, good accessibility with fiber transmission, and high degree of automation. When welding thin materials or fine diameter wires, it does not have the re-melting issues that arc welding often encounters.
The battery cells used for power batteries usually follow the principle of "lightweight" and typically use lighter aluminum materials, while also needing to be thinner. Generally, the shell, cover, and bottom are required to be below 1.0mm. Currently, mainstream manufacturers have a basic material thickness of around 0.8mm, which can provide high-strength welding for various material combinations, especially effective when welding between copper and aluminum materials. This is also the only technology that can weld electroplated nickel to copper materials.

2. Difficulties in laser welding process
Currently, aluminum alloy battery shells account for more than 90% of the entire power battery. The difficulty in welding lies in the extremely high reflectivity of aluminum alloy to laser, high sensitivity to porosity during the welding process, and some inevitable defects during welding, the most significant of which are porosity, hot cracks, and spatter.
1. Porosity is easily generated during the laser welding of aluminum alloys, mainly of two types: hydrogen pores and pores generated from bubble collapse. Due to the rapid cooling speed of laser welding, the hydrogen pore issue is more severe, and there is also an additional type of pore generated from the collapse of small holes.
2. Hot crack issues. Aluminum alloys are typical eutectic alloys, and hot cracks are prone to occur during welding, including weld crystallization cracks and HAZ liquefaction cracks. Due to the segregation of components in the weld zone, eutectic segregation can occur, leading to melting at the grain boundaries, which can form liquefaction cracks under stress, reducing the performance of the welded joint.
3. Spatter (also known as flying sparks) issues. There are many factors that cause spatter, such as the cleanliness of the materials, the purity of the materials themselves, and the characteristics of the materials, while the decisive factor is the stability of the laser.
Surface bulges, porosity, and internal bubbles. The main reasons are due to the small core diameter of the fiber or the laser energy being set too high. It is not as some laser equipment providers promote that "the better the beam quality, the better the welding effect"; good beam quality is suitable for deep penetration overlay welding. Finding suitable process parameters is the key to solving the problem.

▲ Sample of laser welded battery cell components

3. Other difficulties
Welding of soft-pack tabs requires high demands on welding fixtures, which must firmly press the tabs to ensure welding gaps. It can achieve high-speed welding of complex trajectories such as S-shaped and spiral shapes, increasing the bonding area of the weld while enhancing welding strength.
The welding of cylindrical cells is mainly used for the welding of the positive electrode. Due to the thin shell at the negative electrode position, it is very easy to burn through. For example, some manufacturers currently use a no-welding process for the negative electrode, while the positive electrode uses laser welding.
When welding square battery assemblies, if the pole or connecting piece is heavily contaminated, the contaminants decompose during welding, easily forming welding spatter and causing holes; if the pole is thin and has plastic or ceramic structural parts underneath, it is easy to burn through. If the pole is small, it is also easy to misalign and burn the plastic, forming explosion points. Do not use multi-layer connecting pieces, as the gaps between layers make it difficult to weld securely.

▲ One of the cell components that require laser welding

If you are looking for more details, kindly visit Battery Laser Welding Machine.