Most Common Types of Laser Welding Explained

Laser welding, also known as laser beam welding (LBW), is a relatively new welding process that utilizes the heat of a laser beam to melt and fuse pieces. But, to weld pieces, this method can use various lasers, modes, and principles.

Each laser type exhibits distinct performance, efficiency, and wavelength characteristics. These will directly affect the applications and cost-effectiveness of the laser welding, so it is crucial to understand the differences.

In this article, we will explain the most common types of laser welding, their fundamentals, and the advantages they offer. Knowing these will significantly help you make an informed choice and choose the correct procedure for your applications.

Laser Welding in Process
Source: https://www.youtube.com/watch?v=Ay_TwpU8mOk

Brief Overview of Laser Beam Welding

Laser stands for Light Amplification by Stimulated Emission of Radiation. Lasers are not a recent discovery, but it took years for scientists to harness the power for industrial applications such as welding, cutting, or engraving.

Over the years, laser beam welding was born. This technologically advanced form of welding utilizes the heat of the laser beam to melt, evaporate, and fuse the pieces.

Laser Welding Process for Steel Sheets
Source: https://www.youtube.com/watch?v=1CFviADjmEs&t

In brief, laser welding utilizes a highly concentrated and focused laser beam to melt, weld, or cut metal surfaces. The laser beam carries an initial energy, but it is insufficient to reach the desired temperatures.

That's why the beam is focused down to a tiny spot. Focusing the laser beam creates extremely high energy density. Depending on the power of the laser and the energy, the beam can either completely evaporate the surfaces (keyhole welding) or melt them, allowing them to fuse as they solidify (conduction welding).

Regardless of the energy, a focused laser beam creates a narrow heat-affected zone (HAZ). Narrow HAZ is ideal when welding thin and heat-sensitive metals that can overheat, distort, or warp when exposed to high heat. Therefore, laser beam welding is a fast, accurate, and high-quality welding method, highly valuable in industries worldwide.

Different Types of Laser Welding

Technological advancements have brought us dozens of innovations in laser welding, including various types. The first lasers were fairly limited, as they produced a narrow range of wavelengths and were relatively inefficient. Newer types have brought better efficiency, adjustable wavelength, and lower maintenance costs.

There are several ways you can group types of laser welding. In this article, we will explore the following types:

• Laser welding based on a gain medium

• Laser types based on output mode

• Types of lasers based on heat and power

• Laser welding types based on wavelength

• Types of laser welding depending on the laser system

• Other variants/types

Let's explore the types and differences.

Types of Laser Based on Medium (Laser Source)

Laser beams can be extracted from a gas, solid, or liquid medium. Depending on the medium, there are two primary types of laser sources used for welding:

• Gas lasers (CO₂)

• Solid-state lasers (Nd:YAG, Disk lasers, Fiber lasers)

Each type shows different results and efficiency, and therefore, various applications. So, let's further explain the most popular types of lasers used in LBW.

Types of Laser Based on Medium (Laser Source)

CO₂ Laser Welding

CO₂ lasers are the first type of lasers used in welding and cutting applications. Some refer to them as legacy lasers, as they are the first of their kind used in welding.

In CO₂ laser welding, the CO₂ laser beam is generated by exciting a mixture of carbon dioxide, nitrogen, and helium gases. That's why this type is known as a gas laser.

Once generated, mirrors and lenses direct and focus the laser beam into a tiny spot, increasing the energy density. CO₂ lasers produce a continuous welding beam that can easily penetrate metals and non-metallic materials.

CO₂ Laser Construction
Source: https://www.youtube.com/watch?v=iHV0yOCJkRw

The CO₂ laser offers several advantages over traditional welding methods. They are much faster, more precise, and produce narrow HAZ, yielding fewer defects and higher-quality welds. CO₂ lasers can produce deep-penetrating welds on thicker, non-reflective steel pieces. Additionally, they can work with non-metallic components and reflective metals, albeit with lower efficiency.

However, CO₂ laser welding is fairly limited when compared to other laser types. Firstly, a laser beam doesn't move through optical fibers, so it offers lower quality compared to other types. It also means it is harder to adapt to robot integration. Additionally, they are the least energy-efficient option. CO₂ lasers have an average efficiency of approximately 5%, meaning that most of the energy used to generate the laser beam is wasted.

Handheld Fiber Laser Welding Process
Photo by @welding.asmr (TikTok)

Nd:YAG lasers are solid-state lasers that use neodymium-doped yttrium aluminum garnet as a gain medium. A solid rod of yttrium aluminum garnet doped with neodymium generates a laser beam with a fixed wavelength of 1064 nm.

The beam runs through fiber optic cables, providing better quality and higher precision than legacy lasers. It also means they can be used for articulated robotic arms and as a part of automated laser welding systems.

Unlike CO₂, Nd:YAG lasers can provide high peak power with excellent pulse control. Pulsing allows them to weld a wide range of materials, including steel, aluminum, titanium, thermoplastics, and composites.

Construction of Nd:YAG laser
Source: https://circuitglobe.com/ndyag-laser.html

Although Nd:YAG laser welding is a proven technology, it is not without its drawbacks. Firstly, these types of lasers have issues with focusing the laser beam on a small point. They are better suited for mold repairs and other applications where a larger focus is not an issue.

Additionally, ND:YAG welding causes thermal management issues. Like CO₂, the process has a very low efficiency of approximately 5%, and it uses consumables such as mirrors and lamps, which require frequent maintenance. Its high and costly maintenance can be a turn-off for many manufacturers.

Handheld YAG Laser Welding on 4 mm Stainless Steel Sheet
Source: https://www.youtube.com/watch?v=ptPynUSQ9AY

Disk Laser Welding

Disk, or disc, lasers are another solid-state laser that is quite similar to Nd:YAG lasers. They use a thin slice or disk of ytterbium-doped yttrium-aluminum garnet crystal as the gain medium to produce laser light at a wavelength of 1030 nm.

Instead of a crystal rod with a low surface-to-volume ratio in Nd:YAG lasers, disc lasers use a very thin crystal disk, ergo the name. This disk is a few hundred microns thick but several millimeters in diameter and coated with a reflective surface.

Using the disk instead of the rod minimizes thermal lensing. Improving thermal management issues enhances the quality of the laser beam, allowing for better focus. Reducing the spot size improves power density, yields deeper penetration, and results in a narrower HAZ.

However, they are also not perfect as they have limitations such as overheating, amplified spontaneous emission, size constraints, high cost, and material limitations. They require larger disks for increased power, reduced Amplified Spontaneous Emission (ASE), and an optimized design to maintain efficiency and minimize noise.

Key Components of Disk Laser
Source: https://laser-welder.net/laser-welding/disk-laser/

Fiber Laser Welding

Fiber lasers are a newer type of solid-state laser that generates and amplifies light within the core of an optical fiber. Optical fiber cable, which is made of silica glass, is doped with a rare-earth element and serves as a gain medium.

The process begins with high-power semiconductor laser diodes, which convert electricity into light. The light is pumped into the fiber cable, and then enters the doped area, also known as Bragg gratings. Photons are excited and amplified, creating a laser beam.

Fiber Laser Diagram
Source: https://www.laserlabsource.com/Solid-State-Lasers/fiber-laser-basics-and-design-principles

Fiber laser welding is highly efficient, precise, and produces high-quality results. The beam runs through an optical fiber, eliminating the need for complex optics, which significantly reduces maintenance costs. Additionally, the beam is highly accurate, and you can focus it to a pinpoint spot.

Depending on the doped elements, fiber lasers can produce different wavelengths. This ability allows them to weld various types of metals, even those with higher reflectivity. They have high beam quality, especially when compared to legacy lasers.

However, fiber lasers are initially expensive. Although they pay off due to better energy efficiency and weld quality, the initial investment is high. Like with any other laser process, fiber lasers struggle with poor fit-up and contamination.

Fibre Laser Welding In Action
Source: https://www.youtube.com/watch?v=o_mogeXz-1Q

Laser Welding Types Based on Output

Lasers can output a beam as a continuous wave (CW) or a pulsed laser. Legacy lasers, such as CO₂, only deliver continuous wave (CW) output, while newer types can toggle between CW and pulsed modes.

Each has different effects on the base metal joint, so knowing the difference is crucial. Here are the explanations.

Pulsed Laser VS CW Laser for Cleaning & Welding
Source: https://www.stylecnc.com/blog/pulsed-laser-vs-cw-laser.html

Continuous Wave (CW) Laser Welding

As the name suggests, continuous wave (CW) laser welding produces a consistent energy laser beam throughout the process. A continuous beam of laser light melts and fuses the surfaces inside the joint to produce welds.

As it provides steady and uniform heat input, CW laser welding is ideal for long, seam welds. Therefore, it can produce smooth, consistent weld seams with minimal interruptions.

Uniform heat input promotes penetration, making it particularly helpful when welding thicker pieces. Additionally, it fosters welding speeds, making it perfect for high-volume industrial production.

Continuous Wave (CW) Laser Welding
Source: https://www.youtube.com/shorts/RR19YrhMJXw

Pulsed Laser Welding

Pulsed laser welding releases energy at a set repetition rate. The laser beam bursts in short pulses rather than continuously heating the joints.

By adjusting several parameters, such as pulse energy, repetition rate, or pulse duration, you can control the heat to reduce heat exposure. Heat control is mandatory for heat-sensitive metals, such as aluminum or stainless steel, which can warp, distort, or lose their corrosion resistance if overheated.

Overall, pulsed laser welding works particularly well with welding thin sheets, delicate wires, and small components. It also works well with reflective or thermally conductive materials, as well as critical applications that require precision, control, and minimal heat input.

Pulsed Laser Welding Enhances Seamless Welds
Source: https://www.youtube.com/watch?v=ib_mjd3jCbY

Laser Welding Types Based on Energy Input

Lasers used for welding can have various powers, ranging from 10-20 W in micro-welding applications, up to 100 kW for heavy-duty, industrial applications. When expressing the power, what also matters is the energy density.

Focusing a high-powered laser beam to a spot creates high energy density, which can melt or completely evaporate the materials. Depending on the energy input, there are two types of laser welding:

Conduction Welding VS Keyhole Welding
Source: https://amadaweldtech.com/blog/laser-welding-modes-conduction-transition-keyhole-welding/

• Conduction laser welding: This method utilizes low-powered lasers, typically rated less than 500W. The energy density is less than 105W/cm2, which is sufficient to melt and fuse the pieces, without evaporating them. The produced energy reaches the melting point, which is sufficient to fuse thinner pieces without the need for additional filler metal. Although it can be slower due to lower heat, it can produce highly visually appealing, nearly seamless welds.

Heat Conduction Welding for Metal Sheets
Source: https://www.youtube.com/watch?v=M_HK_XzYPL8

• Keyhole laser welding: This method utilizes high-powered lasers with an energy density exceeding 105W/cm2. Applying such high heat to the material completely melts and penetrates it, creating a cavity known as the keyhole. Inside the keyhole, metals reach a plasma-like state that exceeds 17,000°F. These temperatures are ideal for thick pieces and high-volume production. That’s why they are often referred to as deep penetration laser welding.

Keyhole Laser Welding with 50kW Laser Power
Source: https://www.youtube.com/watch?v=jNB4Z7MUjd4

Types of Laser Welding Based on Wavelength

Different gain media of lasers produce different wavelengths. Depending on the laser's wavelength, several types of laser welding are available. The most common are:

• Infrared laser welding (1064 nm): Most older and commonly used lasers are in the group of infrared or near-infrared spectrum. These are suitable for mild steel and materials with low reflectivity. However, on materials such as copper, they have nearly 90% reflectivity.

• Green laser welding (532 nm): After years of research, scientists have discovered that a lower wavelength can work more effectively on reflective surfaces and significantly improve absorption. Lasers that produce green light offer an absorption rate of approximately 35–40% on a reflective surface.

• Blue laser welding (450 nm): Scientists took it a step further by lowering the wavelength to enhance the absorption rate, resulting in the development of blue lasers. Blue laser welding operates similarly to conduction or keyhole welding, improving both quality and speed. The absorptivity of blue lasers on reflective surfaces reaches 60%.

• Ultraviolet laser welding (355 nm): Ultraviolet lasers operate at a significantly lower wavelength compared to other types of lasers, using this energy to heat and fuse materials. They offer precise, high-quality beams specialized in materials like plastics, glass, and certain metals.

Laser Types and Wavelengths for Welding
Source: https://www.xometry.com/resources/sheet/laser-wavelength/

But why is this important? The wavelength of the laser beam directly affects the absorption rate. The concern is the highest with reflective materials, such as aluminum or copper.

Laser welding these metals is very challenging, as they reflect most of the beam. Therefore, you need intense power to weld thin pieces, making it cost-ineffective. Thus, the scientists devised a solution by adjusting the wavelength.

Laser Welding Aluminum
Source: https://www.youtube.com/shorts/jUbATiD2S8I

Types of Laser Welding Based on Machine Complexity

The first laser welding machines were complex, state-of-the-art systems that required specialized expertise to operate and utilize. However, laser technology is becoming readily available, so we are seeing more straightforward solutions.

Based on equipment complexity, there are several types of laser welding available:

• Handheld laser welding: Handheld laser systems are a newer type that is gaining popularity among less experienced welders. They use a power source and a handheld laser gun, which is quite similar to arc welding methods, such as MIG welding. It provides an easy-to-use approach to laser welding basics.

Handheld Laser Welding Thin Aluminum
Source: https://www.youtube.com/watch?v=0Ts4BuEMyYY&t

• Semi-automated laser welding: Small, semi-automated stations are ideal for small production batches. Operators load the parts, while the machine automatically welds the pieces.

• Fully-automated laser welding: Larger, fully-automated robotic laser welding systems designed for mass production. Robot arms move and position clamping tools during laser welding, helping manufacturers scale up production and improve quality.

Fully Automated Laser Welding Process
Source: https://www.youtube.com/watch?v=ss5_cU7aqzw

Other Laser Welding Variants

• Laser spot welding: Similar to resistance spot welding, laser spot welding uses the energy of the beam to join two metal surfaces at a single spot. The beam focuses the energy to produce tiny, spot-like welds, fusing metal surfaces together. It can work with various metal types or dissimilar metals.

Laser Spot Welding in Process
Source: https://www.youtube.com/shorts/aBtZsK2H9dw

• Laser seam welding: This laser welding method produces long, continuous welds along the surfaces by overlapping spot welds. This technique utilizes a laser with a constant or rapid-pulsed beam. Overlapping multiple spots yields high-strength, leak-proof seals, which are ideal for precision applications like medical devices, aerospace, and automotive components.

• Hybrid laser welding: Laser welding is impressive, but it has drawbacks. The method struggles with poor fit-up and wide gaps, so scientists devised a solution to address these issues. They combined arc welding methods such as MIG and TIG with laser welding in a hybrid laser welding process. Two arcs and added filler metal combine the advantages of both laser welding and arc welding, while eliminating their drawbacks.

Precision Laser-Hybrid Welding for Metal Parts
Source: https://www.youtube.com/watch?v=toquox5ipiM&t

Final Thoughts

While lasers are not new, laser welding surely is one of the newest and most advanced welding methods. The first lasers offer significantly higher speed, better precision, and improved weld quality compared to traditional welding, but the technology continues to evolve.

New laser types brought even better efficiency and the ability to weld reflective metals. As a result, laser welding is becoming an essential part of various industries, including automotive, aerospace, battery making, energy, and medical device manufacturing.

Understanding the types of lasers helps you know where they shine and which one is best suited for your applications. Knowledge is power, so ensure you comprehend the basics to make an informed decision.

Laser Welding Techniques on Steel
Source: https://www.youtube.com/watch?v=RHHdfECOeQU&t

🧐 Most Common Types of Laser Welding Explained FAQ