Laser Welding Tips for Beginners

Laser welding is an advanced welding technique widely used across industries for its precision, accuracy, and high-quality welds. Today, the technology is advancing and adapting to smaller-scale use and less experienced users.

As a result, we are seeing more small, handheld lasers that bring ease of use. These significantly increased the number of people using laser welders.

That's why we compiled an article with essential laser welding tips for beginners. From fundamentals to essentials, this article covers everything you need to know to get into laser welding, even if you are an absolute beginner.

Laser Welding Basics

Laser beam welding (LBW) is a joining process that uses the heat from a high-powered, focused laser beam. A gain medium (solid-state or gas source) produces and amplifies the laser beam. The beam is then transported using an optical fiber or a series of mirrors and lenses.

The key point to reaching the required heat is to focus the laser beam to a tiny spot. Focusing the beam creates high energy density. Depending on the density, laser welding can be a conduction welding or keyhole welding.

Conduction welding occurs at the surface because the beam doesn't fully penetrate or vaporize it. Keyhole welding, on the other hand, occurs at high energy. The beam vaporizes the surface, creating a cavity known as a keyhole, which gives the feature its name.

Schematic of Conduction and Keyhole Welding Modes
Source: https://www.researchgate.net/figure/Schematic-of-conduction-and-keyhole-welding-modes-45_fig2_369749519

Depending on the equipment and laser, the beam can be continuous or pulsed. Continuous-wave (CW) laser welding is straightforward because the laser delivers a steady, uninterrupted beam. Pulsed laser welding provides short bursts of energy. Similar to arc welding, pulsing reduces the overall heat exposure to the heat-affected zone (HAZ), making it ideal for thin, delicate metals.

Continuous-wave Laser Welding and Pulsed Laser Welding
Source: https://www.youtube.com/shorts/74FZBbt-95A

In general, laser beam welding is a highly accurate, powerful, and high-quality welding method. Lasers can produce some of the most visually appealing welds, but many avoid the process due to its complexity. But laser welding, especially with the new systems, is much easier to use, so let's learn helpful tips and tricks.

Essential Laser Welding Tips and Tricks for Beginners

Laser welding is indeed more complex than traditional arc welding, but once you get the hang of it, it can be highly rewarding. The key lies in understanding the basics and the limitations of the process.

To give you a head start, we compiled essential laser welding tips for beginners that can also help experienced welders get the most out of it. Without further ado, let's learn more.

1. Thoroughly clean the surfaces for laser welding

Laser welding is a pristine process, but it requires squeaky-clean surfaces to get the best results. In a nutshell, a laser beam is amplified light, and its penetration depth depends on the metal's absorption rate.

Dirt, grease, dust, oil, or other contaminants on the surface can absorb or reflect a fraction of the laser beam, reducing overall penetration. Additionally, burning off contamination can create porosity or compromise weld integrity.

Unlike some arc welding methods, such as Stick welding, LBW does not tolerate any surface contamination. Oxide layers, particularly on aluminum and stainless steel, can significantly increase the risk of weld defects. Therefore, before any laser weld, thoroughly clean the surfaces to avoid defects.

2. Control the gap and secure parts

Laser beam welding is highly vulnerable to uneven or too wide gaps across the joint. Poor gap management and control can create:

• Uneven penetration across the joint.

• Lack of filler metal to bridge the gap, which results in a lack of fusion and penetration.

• Undercut, holes, or other defects caused by poor alignment and bad gap control.

• Uneven strength and reduced tensile shear strength can cause premature failure.

Control the Gap before Laser Welding
Source: https://www.youtube.com/watch?v=fMcJmiIdpPM&t

A rule of thumb in laser welding is that the gap between two components in a lap weld configuration should not exceed 10% to 20% of the thickness of the thinner material. But keep in mind that exact tolerance can vary depending on the specific material and applications.

However, scientists addressed the challenges of gap bridging by combining laser and arc welding methods, such as MIG welding. The MIG wire perfectly fills larger gaps, while the laser provides sufficient penetration and heat control. Using Hybrid Laser Arc Welding (HLAW) is much more forgiving, but it takes some time to learn to control the parameters.

Hybrid Laser Arc Welding in Process
Source: https://www.youtube.com/watch?v=WtNZrh9Dgwk

Since the original laser welding is vulnerable to gap differences, you should always secure parts before welding. Clamps or fixtures will hold the parts firmly in place during laser welding, eliminating the risk of movement and creating uneven gaps.

3. Shielding gas management and coverage

During welding, heated, molten metals tend to pick up atmospheric gases and contaminants. Gases such as oxygen or hydrogen cause oxidation and porosity, which compromise the structural integrity of the weld.

To address this issue, laser beam welding typically uses an external shielding gas. Gases such as argon, helium, or nitrogen create a protective shield around the laser beam, preventing contaminants from reaching the weld.

Close-up of Clean Laser Welds
Source: https://www.youtube.com/watch?v=sqEOGev6clU

Laser beam welding has another issue. Melting the pieces with a laser beam can cause ionization, creating a plasma-like state. This state distorts and reflects the laser beam, affecting the welding results.

The solutions are shielding gases with high plasma suppression (low ionizing potential), such as argon, helium, or nitrogen. These gases are inert and have low ionizing potential, allowing you to weld without the risk of contamination or plasma interference.

Laser Welding Gas Coverage

Besides gas choice, consider coverage as well. Laser welding uses either side or coaxial gas coverage, depending on the application. Side gas delivery is simpler and better suited to straight welds. The coaxial method provides shielding around the beam. It gives much better coverage on intricate designs, but it is more complex.

Like in arc welding, flow rates matter. Besides expenses, using a gas flow that is too high can cause turbulence that sucks in the contamination. Conversely, using a flow rate that is too low can be inefficient.

Coaxial and Side Axis
Source: https://www.osprilaser.com/news/coaxial-vs-side-axis-which-laser-welding-head-85135324.html

Keep in mind that in some high-end industries, laser welding can be done without shielding gas. Micro-welding electronics or batteries occurs quickly and at low heat, often safely avoiding atmospheric contamination. Also, there are instances in which laser welding is performed in a vacuum or an inert atmosphere. But that's reserved for state-of-the-art applications.

4. Properly focus the laser beam

Focusing the laser beam onto a small area creates a spot that melts and fuses the pieces. The smaller the spot is, the higher its energy density, but it covers less area. Therefore, determining the spot size depends on the applications.

As noted, small spots carry extremely high energy density. This energy deeply penetrates the pieces, creating a very narrow heat-affected zone and increasing accuracy, making it ideal for intricate designs. However, such a small coverage is inefficient in geometries with a larger gap.

Larger spots have lower energy but cover a wider area. As a result, they provide more even heat over a larger area, which is beneficial for surface welding or joining materials with different thermal properties.

Also, don't forget about setting the focal point to control weld quality. In most applications, welders use focus zero, in which the laser focal point is at the material surface. However, you can adjust the focus slightly above or below the surface to mitigate issues like spatter or porosity.

5. Test power, and balance it with speed

After adjusting the power and focus, use scrap metal to ensure it melts without causing excessive heat or burn-through. Running a practice bead will help you fine-tune the parameters and avoid wasting pieces or time on rework.

Keep in mind that speed and power are related in welding. Laser welding is known for its speed, but running the beam through welds without allowing it enough time to melt the pieces can result in insufficient fusion and penetration.

Meanwhile, going too slow increases heat exposure. Spending too much time in one place increases heat input, potentially leading to overheating. Overheating leads to oxidation on corrosion-resistant metals or a complete burn-through. Seeing holes in your welds is never a good sign, so it is always better to test first, then weld actual pieces.

6. Always consider the composition and metallurgical properties of metals you are welding

Understanding the properties of the metal you are welding is crucial in making the right approach. Alloying elements can make certain metals much more weldable or more challenging to weld.

For example, welding medium or high-carbon steel can be a nightmare, even for heat-controlled processes such as laser welding. While carbon improves the strength and hardness of the metal, it leads to the formation of martensite during rapid heating and cooling. The martensite microstructure is hard but brittle, leading to cracking during solidification.

Brittle Martensite in High-Carbon Steel Laser Welds
Source: https://www.nist.gov/image/laserweldleapjpg

On the other hand, alloying elements such as manganese improve ductility. Improved ductility makes the microstructure and metal much more forgiving and easier to weld. Magnesium and silicon influence the alloy's response to heat treatment, also affecting the weldability.

Therefore, there is no one-size-fits-all approach in laser welding. When welding challenging metals, such as high-carbon steel, consider using core/ring fiber lasers, which can provide pre- and post-heat treatment benefits. If you are welding thin or delicate metals, heat control is crucial. Consider using pulsed welding to limit the heat exposure and reduce the risk of warping or burning through.

7. Reflectivity is your greatest enemy

Not all metals are easily laser-welded, and many of the limitations result from reflectivity. As previously noted, the laser beam is an amplified light. As it hits the metal surface, it either absorbs or reflects.

The more metal absorbs the beam, the deeper it can penetrate. But metals with shiny surfaces, such as aluminum or copper, can be a nightmare to laser weld as they reflect most of the energy.

As the beam hits the shiny surface of aluminum or copper, most of it reflects, while only a portion is absorbed. Therefore, to reach the heat required to melt and fuse the pieces, you need to turn up the power.

Laser Welding of Aluminum
Source: https://www.youtube.com/watch?v=UqvCoZfXepg&t

However, keep in mind that turning up the power can be utterly cost-inefficient, especially with traditional lasers. These have an efficiency of approximately 5%, so they spend a lot of energy to produce sufficient power, increasing the overall welding costs.

Nonetheless, scientists developed solutions for reflectivity. If you frequently weld reflective metals, consider investing in a blue or green laser. Green lasers emit at ≈532 nm, and blue lasers at ≈450 nm, which significantly enhance absorption in highly reflective metals. However, remember that these can be expensive for everyday applications.

8. Avoid spatter

Laser welding requires immaculate cleanliness, and spatter is uncommon. Quite the contrary, excessive spatter is a sign that you are doing something wrong, so you should address it at all costs. In laser beam welding (LBW), spatter results from excessive power, an inappropriate shielding gas, or incorrect alignment.

As the laser's power increases, it starts to melt and aggressively evaporate the pieces. Molten metal droplets fly away from the weld pool and stick to the surface. If you see an aggressive puddle with excessive spatter, try turning down the power.

Spatter in Laser Welding Process
Source: https://www.youtube.com/watch?v=xZYYmL54oUU

The power is often related to focus and energy density. Adjusting the laser focus can help control the energy density at the weld site. Controlling the density is crucial in avoiding excessive spatter.

If the power is fine, but the molten metal still flies around, check the shielding gas. Semi-reactive or reactive gases can improve penetration, speed, and weld-puddle fluidity, but they lack plasma suppression. Higher ionization potential, combined with beam energy, creates a plasma-like state that causes spatter, among other effects.

If the wrong gas creates a spatter, switch to inert shielding, as it provides unmatched protection. Delivery method and rate can also cause excessive spatter.

9. Fill the crater

Prematurely finishing the laser welds can create a defect known as a crater. This issue also occurs in arc welding when you remove the torch before filling the end of the weld joint.

Craters can develop cracks that eventually compromise the weld's structural integrity and lead to failure. These are especially prevalent in steel welding, but are also frequently seen in some aluminum alloys.

Crack in AZ91D Laser Welding
Source: https://www.mdpi.com/2075-4701/11/7/1127

To address this issue, make sure to spend enough time at the end of the weld. As you do so, there is a risk of overheating, as you will be slowing down.

So, consider using a laser that has a built-in ramp-down option. Ramp-down gradually reduces energy as you finish the weld, allowing you to fill the crater appropriately.

10. Protect yourself and your laser components

Besides a lack of power, welding reflective metals can damage your eyes or the components of your laser welding system. Laser beam light is not the same as an arc, so you'll need specialized personal protective equipment (PPE) designed for laser welding.

To protect yourself, you will need certified laser safety glasses or goggles designed for the specific laser wavelength, often underneath a laser welding helmet. A laser welding helmet is mandatory as it protects you from intense light, heat, and radiation. Other PPE, including a jacket, a long-sleeved shirt, and protective boots, is standard in most welding methods.

When it comes to components, an intense reflected beam can damage optics, which leads in turn to thermal lensing. Thermal lensing can affect laser focusing, reducing power density and penetration.

To prevent lens damage, use a protective lens coating and high-quality glass. Anti-reflective and high-durability coating minimizes damage. High-quality glass designed for the wavelength and power level of your laser system will reduce optical absorption.

11. Don't ignore maintenance

Regular maintenance will significantly affect the stability and quality of your welds. Ensuring each component is in top-notch condition will help you achieve the best welds every time.

As a regular maintenance, make sure you periodically check coatings and optics. Check for signs of damage or contamination and replace them immediately to ensure proper performance.

Also, measure laser power daily to detect gradual degradation. If noted early, you can implement corrective actions before the power imbalance affects weld performance. Regular calibration ensures consistency, yielding the highest-quality laser welds every time.

12. Data logging and monitoring

Most newer laser welding systems, especially those used in industry, use advanced sensors for data monitoring, logging, and analysis. A series of smart sensors can detect issues, log welding parameters, and the part's condition.

For example, in-process monitoring tracks the key welding parameters during the procedure. They monitor power, surface temperature, plasma emission, and more to provide real-time feedback. Some advanced systems make adaptive changes when the conditions change, while more basic ones will give you a warning, and you manually change the parameters.

Laser Welding Data During Welding
Source: https://www.youtube.com/watch?v=v_-cSfgtMJQ

Cross-sectional analysis and CT scanning can detect internal defects. You can employ NDT methods such as ultrasonic testing, liquid dye penetrant inspection (DPI), or radiographic testing (RT), to check the internal structure for discontinuities, defects, or inclusions.

Finally, data logging allows you to establish a comprehensive database of process data. Long-term tracking of laser power, speed, gas flow, and temperature enables you to identify trends, detect potential issues, and optimize welding parameters.

Statistical process control (SPC) charts can help monitor process stability and detect deviations. These can identify degradation or anomalies, allowing you to address the issues and schedule preventive maintenance. Scheduled maintenance reduces downtime and risk of unexpected part breaking.

Final Thoughts