What Metals Can You Laser Weld?

Laser welding is a remarkable joining method widely used in industries worldwide. Arc welding methods cannot match the accuracy, high speed, and weld quality of lasers, which is why it is gaining popularity across the globe.

However, laser beam welding is still a relatively new and complex method, so many interested manufacturers have doubts. Among others, one question that often emerges is: What metals can be laser-welded?

Lasers can join virtually any metal, but due to the nature of the process, it may require significantly more power to produce welds on certain metals. In this article, we will further explain how lasers interact with different metals, so stay tuned to learn more.

Quick Overview of Laser Beam Welding

Laser welding uses a high-powered, focused laser beam to melt and fuse metals or thermoplastics. A laser source generates a laser beam from media such as gas (CO2 lasers), solid crystals (Nd:YAG lasers), or other sources, including fiber lasers, IR lasers, or diode lasers.

Regardless of the source, the initial laser beam carries high energy, but it is insufficient to melt and fuse the pieces on its own. Instead, a laser beam is transported through an optical fiber, directed and focused by a series of mirrors and lenses.

Focusing the laser beam down to a tiny spot creates extremely high energy density. Lower energy beams melt and fuse the thin sheet pieces. A high-energy laser beam completely evaporates the surface, creating a cavity known as a keyhole, which works particularly well on thick metals.

What Factors Affect the Weldability of Metals?

LBW uses a laser beam as a heat source that melts and fuses the pieces. Meanwhile, arc welding methods such as TIG or MIG Welding use an electric arc.

The very nature of laser welding affects the weldability of specific metals, with the most crucial factors being:

• Optical properties of metal: A laser beam is fundamentally a form of light, so once it hits shiny surfaces, a portion of it bounces off. Depending on the reflectivity of metal surfaces, only a tiny fraction of the laser beam can heat the pieces, while the rest goes to waste. Laser welding is ideal for pieces that absorb the beam, rather than reflect it.

• Thermal properties of metal: Properties such as melting point, thermal conductivity, or thermal expansion significantly impact the performance of a laser. For laser welding, materials with a low melting point, high thermal conductivity, and low thermal expansion are ideal.

• Chemical properties of metal: Properties such as composition, purity, and compatibility with other materials can also affect weldability. Metals with homogeneous and consistent composition, high purity, and low susceptibility to oxidation are ideal for laser welding.

So, let's discuss the metals that lasers can weld.

What Metals Can Be Laser Welded?

You can laser weld virtually any metal, and also some thermoplastics (acrylic, PVC, PC plastics, or composites). However, due to thermal, metallurgical, optical, and chemical properties, some metals can be much more challenging to laser weld than others.

Acrylic Welding with Diode Laser Sources
Source: https://www.youtube.com/watch?v=gU-dKxfuAv0

Easy-to-laser-weld metals include :

• Die steel (Tool steel)
• Mild steel (Low-carbon steel)
• Stainless steel
• Titanium (With proper shielding)
• Nickel alloys
• Low alloy steels

Metals that are challenging to laser weld are :

• Aluminum
• Copper and copper alloys
• High-carbon steels
• Magnesium alloys
• Galvanized steel

Let's learn more about why some metals are easier to laser weld than others.

Laser Welding Mild Steel

Mild steel, or low-carbon steel, is a metal with a carbon content lower than 0.25%. Low carbon content provides excellent weldability, making mild steel one of the most weld-friendly metals, and that also applies to laser beam welding.

Mild steels don't have a reflective surface or high thermal conductivity. They quickly absorb laser light, allowing it to penetrate, melt, and fuse the pieces. You don't need a lot of power to do it, and they offer predictable melting and solidification, as well as reasonable weld pool control.

Due to their versatile properties and applications, mild steels are ubiquitous. You can find them in general fabrication, automotive structures, construction, and various other applications. The best part about them is that you won't have a hard time welding them. However, parameter control, laser focus, and direction are crucial in achieving high-quality, accurate, and immaculate laser welds.

Die Steel Laser Welding

Die steel is a specialized type of high-carbon steel. This metal is specifically designed for tools and dies used in manufacturing processes such as forging, rolling, extrusion, and wire drawing. Compared to mild steel, these metals exhibit high hardness and wear resistance, making them ideal for industrial applications.

Overall, you can readily laser weld various die steel types, such as S136, SKD-11, NAK80, 8407, 718, 738, H13, P20, W302, and 2344 tool steels. Due to its higher hardness and strength, welding die steel often requires a heat treatment to reduce thermal stress, which can increase the risk of cracking.

Otherwise, laser welding works well with tool steel. High-power lasers can produce deep-penetrating and robust welds, which are essential in mold making and die casting. Besides regular preparation, heat treatment, and parameter tuning, nothing else prevents the laser beam from penetrating the die steel.

Stainless Steel and Laser

Metal fabricators frequently utilize stainless steel in applications that necessitate exceptional corrosion resistance. The added chromium protects the metal from corrosion and also gives it a unique appearance.

Stainless steel has low thermal conductivity, a high energy absorption rate, and high melting efficiency. These properties can result in a significant linear expansion coefficient during welding. You might have heard some welders say stainless steel distorts, even if you look at it wrong.

However, in laser welding, mirrors and lenses focus and converge the laser beam into a tiny spot. Besides accuracy, this spot creates a very narrow heat-affected zone (HAZ), significantly reducing the risk of overheating, warping, and distortion. Stainless steel exhibits good laser absorption, enabling the production of solid and high-quality welds.

As a result, low-powered lasers can successfully weld thin stainless steel sheets without the risk of distortion, warping, or porosity. Additionally, you can create smooth and aesthetically pleasing stainless steel welds with a laser.

Titanium Welding

Titanium is a lightweight metal with excellent corrosion resistance and the highest strength-to-density ratio of any metallic element. More importantly, titanium is a highly nonreactive substance, making it ideal for medical implants and aerospace components.

However, titanium has a great chemical affinity for combining with oxygen. This property provides excellent corrosion resistance; however, heating it to its melting point during welding can contaminate the weld pool. An unprotected weld puddle will result in an impure and weak weld.

Titanium Alloy Laser Welding in a Glove Box
Source: https://www.youtube.com/shorts/A2i5c-wnOiw

Otherwise, titanium shows exceptional laser weldability. As long as the molten weld puddle is protected by high-purity inert shielding gas, you can readily laser weld titanium. Welders often weld titanium parts in a laser welding glove box filled with pure gas to provide sufficient gas coverage.

Therefore, titanium is somewhere in between when it comes to welding difficulty. Laser welding itself is not particularly demanding, but providing excellent shielding gas protection can be a challenge for some welders.

Nickel Alloys and Laser

Nickel and its alloys, such as Inconel, Monel, and Hastelloy, are renowned for their superior strength at elevated temperatures and for having high resistance to corrosive environments. Alloying elements such as titanium, aluminum, chromium, iron, molybdenum, or cobalt provide outstanding mechanical properties.

Additionally, they provide good metallurgical properties for welding and laser absorption. Lasers used in nickel alloy welding offer numerous advantages, including smaller heat-affected zones and enhanced precision control.

Overall, laser welding nickel alloys isn't a daunting task, as you can easily avoid cracking or other structural defects. Nonetheless, sound welds require optimal control of welding parameters and the proper selection of filler material. Doing so can play a significant role in enhancing weld quality and joint performance under service conditions.

Alloyed Steel Welding

Lasers can readily weld alloyed steel, including low-alloy high-strength (HSLA) steels. However, the results may vary depending on the alloying elements (commonly carbon).

The high energy density of laser welding produces deep penetration and narrow welds in alloy steels. Deep-penetrating welds are particularly beneficial for attaining high tensile strength in HSLA steels. The welds can match or even exceed the properties of the base metal if needed.

Of course, like with other metal types, laser welding low-alloy steel requires careful attention to welding parameters and material characteristics (especially carbon content). Preparing will help you avoid potential cracking and reach optimal results.

Laser Welding Aluminum

Aluminum is a lightweight, corrosion-resistant metal that is favored by numerous industries worldwide. However, its properties make it one of the most challenging metals to weld, especially with traditional arc welding methods.

One of the primary challenges arises due to aluminum's high thermal conductivity. Aluminum has roughly five times the thermal conductivity of steel, meaning it dissipates heat more effectively. The heat spreads from the welding joint. So, instead of melting the pieces inside the joint, it heats the surface, causing warping or distortion.

Aluminum Block Welding with a 2000W Laser Welder
Source: https://www.youtube.com/watch?v=O2laAmmXTOw

Aluminum also has a relatively low melting point. While this sounds advantageous, failing to control the heat can cause burn-through. Combined with high thermal conductivity, it takes the perfect amount of heat to melt and fuse the pieces without error.

When it comes to laser beam welding, aluminum poses another challenge. The aluminum surface is highly reflective, meaning a portion of the laser light is deflected. Deflection causes a loss of power and efficiency, and combined with high thermal conductivity, it requires a significant amount of power to melt and fuse aluminum pieces.

On thin aluminum sheets, this loss of power in the laser is negligible. Quite contrary, the precision, narrow HAZ, and heat control of lasers can be advantageous in sheet aluminum welding. Laser beam welding is a clean process, which is highly favorable in aluminum welding.

However, welding moderate aluminum thickness requires high-powered lasers. These lasers consume a significant amount of energy, with only a portion of it being transferred into the weld joint, thereby reducing overall efficiency and increasing costs. For example, a high-powered industrial laser that can weld up to 3/4" thick steel can weld up to 1/2" aluminum.

Laser Beam Welding Copper and Its Alloys

Lasers offer a fast and precise means of welding copper. However, copper is another notorious metal in laser welding, due to its extremely high reflectivity and thermal conductivity.

1mm Copper Flat Angle Laser Welding
Photo by @peslamfoz7w (TikTok)

Firstly, the surface of copper is extremely reflective, meaning it deflects most of the laser light. To produce welds, the metal surface must be able to absorb light. With copper, the percentage of absorption depends on the wavelength of the light. Generally, copper reflects nearly 95% of infrared radiation.

Additionally, copper has extremely high conductivity, both electrical and thermal. That means parts dissipate the heat rather than focusing it solely on the welding joint. At the melting point, copper becomes highly absorptive, increasing the risks of blow-outs and spattering.

Therefore, to successfully laser weld copper, you would need a laser with at least 2 kW of power. Similar to aluminum, this laser could weld much thicker mild steel or stainless steel, but due to copper's properties, the thickness is relatively limited.

Copper Welding with a 4000W Portable Laser Welder
Source: https://www.youtube.com/watch?v=nSyoLAqD7SM

The solution to copper's high reflectivity lies in green and blue lasers:

• Green lasers produce green light (wavelength ≈532 nm), which yields an absorptivity of ≈35–40%.

• Blue lasers deliver blue light (wavelength ≈450 nm) for an absorptivity of ≈60%.

These come either as DPSS lasers (diode-pumped solid-state lasers) or laser diodes. Both have their ups and downs, but they directly solve the issues with copper's reflectivity. However, whenever possible, manufacturers tend to use standard, fiber lasers and deal with copper's properties by gradually pumping up the power.

High-carbon Steel Laser Welding

Unlike mild steel, high-carbon steel contains a carbon content ranging between 0.60% and 1.5%. Increased carbon content improves steel's strength and resistance to wear and tear, making it ideal for cutting tools, springs, and high-strength wires.

However, as the carbon content increases, the metal becomes more challenging to weld. Rapid heating or cooling of the welded pieces will cause cracking, even if you do everything right. Cracking is an issue with any welding method, including laser welding. Although laser beams limit the heat input and provide low-hydrogen solutions, welding high-carbon steel can be highly unpredictable.

High-Carbon Steel Laser Welding
Source: https://www.youtube.com/watch?v=CgDqg7eABs4

To laser weld high-carbon steel, you should heat treat the pieces before and after welding. Preheating the carbon steel to 300-500°F before welding will minimize the initial heat stress. Also, welding carbon steel requires patient postheat treatment and slow cooling. Pieces can take up to 48 hours to slowly cool to ambient temperature.

Preheating and slow cooling will relieve heat stress in high-carbon steel. However, that still doesn't mean you'll avoid cracking. Sometimes, even if you do everything right and control the heat, high-carbon steel still can crack, so it is a hit-or-miss situation.

Laser Welding Galvanized Steel

Galvanized steel is regular steel protected by a layer of zinc, which gives it corrosion resistance and a more visually appealing look. Zinc does not rust and protects the steel from the oxidation process when in contact with air. You can laser weld galvanized steel, but it can be challenging.

The main issue with galvanized steel welding lies in the protective zinc layer. Zinc has a lower melting point than the steel underneath it. As the heat hits the zinc, it starts to evaporate, creating toxic fumes that pose health risks for nearby welders.

Burning zinc also increases the risk of porosity and oxidation inside the weld. In addition, the zinc layer can absorb some of the laser's light. As a result, it can be challenging to produce a well-formed weld seam.

To deal with these issues, you must adjust equipment parameters and optimize welding processes based on the thickness of the galvanized steel and the zinc layer. To keep yourself safe from harmful fumes, you will need enhanced ventilation and protective measures. Adjusting the offset angle of laser beams can help you reduce zinc spatter.

Laser Welding Magnesium Alloys

Magnesium alloys are highly valuable due to their high density and low weight. Magnesium is the lightest structural metal, often found in industries such as aerospace or automotive, where we also encounter laser welding. Laser welding magnesium alloys is quite common in the automotive industry, but it can be challenging.

Laser Welding Magnesium Alloy Dashboard
Source: https://www.youtube.com/watch?v=nOlV4HhGEug

Magnesium and its alloys have a relatively low boiling point. While that characteristic allows low-powered lasers to melt and fuse the pieces, overheating can cause various issues. Magnesium boiling can cause significant evaporation of alloying elements and spatter. Spatter affects the quality of the welds, while the lack of alloying elements can compromise the structural integrity.

Rapid evaporation can also cause instability. Inexperienced welders can have a hard time controlling the weld pool and keyhole, leading to various defects. Among others, porosity, cracking, or oxidation are common in magnesium laser welding.

To deal with these issues, welders need careful attention to process parameters and material characteristics. Heat control parameters, including pulse or laser modulation, can be highly beneficial. You also shouldn't disregard other parameters such as laser power, welding speed, spot size, and focal position.

Final Thoughts

Laser beam welding is a fast, high-quality, efficient, and clean welding method that can produce immaculate welds. Its advantages enable it to weld various types of metals, including the tricky ones such as aluminum.

However, like any other welding process, laser welding works better on some metals than others. Generally, lasers work great with metals that absorb the laser beam, such as mild steel, stainless steel, or die steel.

On the other hand, laser welding is less practical on metals with reflective surfaces, such as aluminum or copper. Light bounces off the surface, while metal absorbs only a portion. Understanding these properties is crucial in optimizing your laser welding performance on different metal types.

🧐 What Metals Can You Laser Weld? FAQ

1. What metals can be laser welded?

You can laser weld many metals, including mild steel, stainless steel, titanium, nickel alloys, tool steel, aluminum, copper, and galvanized steel. Some metals weld easily, while others need more power or tighter parameter control.

2. What makes a metal easier to laser weld?

Metals are easier to laser weld when they absorb laser light well, have manageable thermal conductivity, and do not react strongly with oxygen or contaminants during welding.

3. Can stainless steel be laser welded?

Yes. Stainless steel works very well with laser welding. The focused beam creates a narrow heat-affected zone, which helps reduce warping, distortion, and overheating.

4. Can aluminum be laser welded?

Yes. Aluminum can be laser welded, but it is more challenging than steel because it reflects more laser energy and conducts heat quickly. Thin aluminum sheets are usually easier to weld than thicker aluminum sections.

5. Can copper be laser welded?

Yes, but copper is one of the more difficult metals to laser weld. It reflects a large amount of infrared laser energy and conducts heat very quickly, so it often requires higher power or green/blue laser wavelengths for better absorption.

👏 You may be interested in the following:

• Laser Welding Explained: What It Is and How It Works
• Clean, Cut, Weld: Exploring 3 Major Industrial Uses of Laser
• Common Misunderstandings About Laser Welding