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What Is Laser Welding?

What Is Laser Welding

What Is Laser Welding?

Laser welding is a process that uses a high-precision laser beam to join metals or thermoplastics together to form a weld. As such a concentrated heat source, laser welding can weld thin materials at high welding speeds. In thicker materials, however, narrow and deep welds can be produced between square-edged parts.
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Laser Welding Machine

What Is Laser Welding?

Laser welding or laser beam welding (LBW) is a process that uses a concentrated heat source in the form of a laser to melt materials that fuse as they cool. Laser welding is a versatile process because it can weld thin materials quickly while forming narrow and deep welds on thicker materials.
Laser welding uses a high-precision laser beam to melt metals and thermoplastics, so the accuracy and precision of the process result in low thermal distortion, making it ideal for welding sensitive materials. This process is usually automated, allowing for high soldering rates.
While laser welding machines cost more than traditional welding processes, operating costs are lower because laser welding does not necessarily require additional filler material and post-processing. Plus, higher welding speeds allow more parts to be produced per hour. Laser welding technology is significantly different from traditional arc welding processes such as TIG, MIG, and SMAW. Modern welding applications use programmable robots with advanced optics to pinpoint an area in the workpiece.
Laser Welding Machine

Types of Laser Welding

Laser welding operates in two different modes: heat conduction welding and deep hole welding. They all have unique operating principles suited to specific applications, and the mode in which the laser beam interacts with the material it is welding will depend on the power density at which the beam hits the workpiece.

Heat Conduction Welding

In this method, a focused laser beam is used to melt the surface of the substrate. This process is generally done with a low-power laser below 500W and is mainly used to produce welds that do not require high welding strength. When the joint cools and solidifies, it produces a precise and smooth weld. Welds created using heat transfer methods generally do not require any additional finishing and are ready to use.
In heat conduction welding methods, energy enters the weld zone only by heat conduction, which limits the weld depth, so the process is ideal for joining thin materials. This type of welding is often used for visible welds where aesthetics are desired.
There are two subcategories of heat conduction welding:
  • Direct Heating – The ability to apply a laser beam directly to a metal surface.
  • Energy Transfer – Absorptive ink is applied to the seam to absorb the energy applied by the laser beam.

Deep Hole Welding

Running the process in deep hole weld mode produces deep, narrow welds with a uniform structure. During this process, the laser beam heats the metal in such a way that it evaporates from the contact surface and penetrates deep into the metal. This not only melts the metal but also vaporizes it, creating a narrow, vapor-filled cavity called a keyhole cavity or vapor capillary. As the laser beam passes through the workpiece, it fills with molten metal. Keyhole welding is a high-speed process, therefore, deformation and formation of the heat-affected zone are kept to a minimum.
Laser Welding Machine

Laser Welding Process

Laser welding works by using a high-power density laser to apply heat to the joint between two metal surfaces. The material will melt at the seams and allow fusion between the metals as it solidifies.
Laser welding is typically performed by welding robots that can apply large amounts of energy at high speed and with precision, guided by flexible optical fibers. This results in melting a sufficient amount of metal in the joint to produce a narrow weld with minimal distortion. Handheld laser welding machines are a great alternative to bulky industrial machines, but the safety of laser welders can be challenged and require the wearing of specialized protective gear.
The welding process can be carried out under atmospheric conditions, but for more reactive materials an inert gas shield is recommended to eliminate the risk of contamination. Similar to electron beam welding, laser welding can be performed in a vacuum, but was not considered economically viable. Therefore, laser welders are equipped with gas nozzles that supply inert gas to the welding area.
Many laser welding applications do not require additional filler material. However, some challenging materials and applications require filler materials to produce satisfactory welds. Adding filler material improves the weld profile, reduces solidification cracking, imparts better mechanical properties to the weld, and allows for a more precise joint fit. The filler material can be in powder form or filler wire. However, since the powder is generally more expensive for most materials, it is more common to use wire stock. The four most common types of joints used with laser welding are butt welds, edge flange welds, filler lap welds, and lap welds.
Laser welding can be performed on a variety of metal materials, including mild steel, stainless steel, aluminum, titanium, and more. Laser welding of high-carbon steel is generally not recommended because of the fast cooling rate and the tendency to crack.
Laser Welding Machine

Laser Type

Laser welding machines for welding processes are mainly divided into 3 types: gas laser (CO2), solid-state laser, and fiber laser.

Gas laser (CO2)

The CO2 laser source is a mixed gas, in which CO2 is the main component, and there are nitrogen and helium in addition. These lasers can be operated in continuous or pulsed mode at low currents and high voltages to excite gas molecules. CO2 lasers are also used in special cases such as dual-beam laser welding, where two beams are generated and arranged in series or side by side.

Solid State Laser

Solid-state lasers use diode-pumped solid-state (DPSS) technology to pump minerals such as ruby, glass or yttrium, aluminum and garnet (YAG), or yttrium vanadate crystals (YVO4) through laser diodes to produce laser light. These lasers operate in continuous wave or pulsed beam mode. Pulse mode produces a joint similar to a spot weld but with full penetration. Compared with modern fiber lasers, this type of laser has many disadvantages, but we cannot deny that solid-state lasers still have excellent beam stability and quality as well as high efficiency.
Semiconductor-based lasers are also in the solid state but are generally considered a different class than solid-state lasers. These lasers are only good for cheaper smaller projects. However, they are sometimes used when welding in hard-to-reach areas because the equipment is more compact. The beam quality is much poorer than other types of lasers, so it is not common in industrial environments.

Fiber Laser

Fiber lasers are a new class of solid-state lasers that offer higher laser power, better quality, and safer operation. In a fiber laser, the laser beam is produced when the fiber absorbs the raw light from the pump laser diode. To achieve this transition, the fiber is doped with rare earth elements. By using different doping elements, it is possible to generate laser beams with a wide range of wavelengths, which makes fiber lasers ideal for a variety of applications, including laser welding and laser cutting. However, it is worth noting that standard laser cutting heads cannot be used for welding, and laser welding heads cannot meet the cutting speed and quality requirements of most industrial applications.
Laser Welding Machine

What Are The Safety Guidelines For Using Laser Welding?

Although a handheld laser welder is easy to use and has built-in safety features, it’s important to remember that it’s a powerful piece of industrial equipment. When working on a laser welding machine, keep in mind that the laser beam can be dangerous to the body and eyes. Laser welding beams are invisible light, so you cannot rely on visual cues for safety.
Although laser welding machines are Class IV lasers and safety features are integrated into the system, traditional welding safety requirements also need to be implemented when establishing a laser safety program. Here are some general rules to follow:
  • Wear non-flammable clothing, long sleeves, or a welding suit. Anyone in a laser-controlled area must use personal protective equipment, including laser safety glasses appropriate for the type of laser and a conventional welding helmet.
  • Please follow operating safety procedures, taking into account that the laser light may be reflected.
  • Never operate a handheld laser welding machine until you are fully familiar with the safety requirements and procedures documented in the equipment manual provided by the manufacturer.
Automatic Wire Feeder

Advantages of Laser Welding

  • Excellent weld quality due to low heat input and precise laser power control.
  • Fast welding speed and low unit cost.
  • Larger welding depths form high-strength welds.
  • Allows welding material combinations that cannot be joined by other methods.
  • Simple welding equipment allows welding under special conditions.
Laser Welding Machine Automatic Wire Feeder

Disadvantages of Laser Welding

  • The initial investment is high.
  • Tight tolerances require perfect workpiece fit and laser alignment.
  • Materials with high reflectivity and conductivity (aluminum and copper) can produce complex welding results (in the case of CO2 lasers).
  • Rapid solidification may result in porosity and brittleness.
  • Laser optics are very fragile and can be easily damaged.
Laser Welding Sample

Laser Hybrid Welding

Laser hybrid welding combines the welding methods of electric arc and laser beam. The two welding methods act on the same welding area at the same time, so the welding effect has the advantages of arc and laser beam welding, creating a unique welding process. Although laser welding can be used in conjunction with almost any arc welding process, there are a few processes that stand out and are more commonly used.
There are three main types of laser hybrid welding:
  • MIG additive welding (often synonymous with laser hybrid welding)
  • TIG additive welding
  • Plasma arc welding
The hybrid welding process offers the deep penetration of laser welding and a weld cap profile comparable to arc welding processes. The use of shielding gas and other arc welding consumables allows for better control of weld characteristics than laser welding itself. Laser hybrid welding is undoubtedly an emerging process that will be used more and more in the shipbuilding, railway, automotive industries, and large pipeline welding projects in the future.

Frequently Asked Questions

Does Laser Welding Need Gas?
Lasers can be performed with or without gas, depending on the application and the material being welded. In some cases, a shielding gas such as argon, helium, or nitrogen can be used to create a shielding atmosphere around the welding area. This is especially important when welding oxidation-sensitive materials such as titanium or aluminum. The type of gas used depends on the material being welded, the welding process, and the equipment used.
In some cases, a gas mixture can be used to achieve a specific welding effect. For example, a mixture of helium and argon can be used to weld stainless steel, while nitrogen is often used to weld aluminum. The use of gas is an important aspect of laser welding and contributes to the quality and reliability of the weld.
Yes, laser welding is a robust and reliable welding method. Laser welding uses a highly focused laser beam to melt and fuse metal surfaces to form a strong, high-quality bond. The heat generated by the high-power laser beam is highly concentrated, resulting in minimal deformation and a very narrow heat-affected zone.
The strength of laser welding depends on a variety of factors, including the type of metal being welded and the specific welding process used. Proper preparation and welding parameters such as laser power, speed, and pulse duration must be carefully controlled to ensure a strong and reliable weld. In general, laser welding is particularly effective for welding thin materials because it minimizes the heat and distortion generated during the welding process.
Laser welding is commonly used in applications where strength and precision are critical, such as aerospace, automotive, and medical device manufacturing. It’s worth noting, however, that weld strength also depends on proper weld design and execution, so it’s critical to involve experienced welders and engineers in the process.

Laser welding is a high-precision welding method that can be used to join many different types of metals, including:

  • Steel: Laser welding is commonly used to weld various grades of steel, including mild steel, stainless steel, and high-strength steel because it can provide high-quality welds with low heat input.
  • Aluminum: Laser welding is an effective method for welding aluminum because of its high reflectivity and thermal conductivity.
  • Copper: Laser welding is also effective for welding copper and brass, while traditional welding techniques are difficult to weld copper, they are often used in electronics and plumbing applications.
  • Titanium: Laser welding is often used to weld titanium because of its high melting point and reactivity.
  • Gold And Silver: Laser welding can also be used to weld precious metals such as gold and silver, which are often used in jewelry making and other high-end applications.
  • Nickel And Its Alloys: Laser welding can be used to weld nickel and its alloys, such as Inconel, which is often used in aerospace and other high-performance applications.
  • Magnesium: Magnesium is a light metal that can be welded using lasers, especially in the automotive and aerospace industries.

Laser welding is a versatile welding method that can be used to join a wide variety of metals, both ferrous and non-ferrous. However, the exact suitability of laser welding for a particular metal will depend on the specific properties of the metal and the requirements of the welding application.

Generally, laser welding does not use welding wire. Unlike other types of welding processes such as MIG (metal inert gas) or TIG (tungsten inert gas) welding, laser welding does not require a filler material like welding wire to join two pieces of metal together. Laser welding uses a focused, high-intensity laser beam to melt and join two pieces of metal together. The heat generated by the laser beam is usually sufficient to melt the metal without additional welding material.
In some cases, however, a small amount of filler material may be added to the joint to increase its strength or to help fill the gap between the two parts being joined. This filler material is usually in wire or powder form and is added to the joint by a manual or automated process. Additionally, some laser welding techniques, such as hybrid laser welding, may use welding wire to create a more stable arc and reduce spatter.

Laser welding is a widely used process in various industries including automotive, aerospace, and medical. Although laser welding has many advantages such as high precision, fast speed, and small deformation, there are also some potential defects in the welding process. Some pitfalls of laser welding include:

  • Porosity: The formation of small voids or pores in the welding material, caused by gases trapped during the welding process, which can weaken the welded joint and reduce its strength.
  • Cracks: Laser welding can create a highly concentrated heat-affected zone, which can lead to the cracking of the welded material, especially if the material has a high thermal expansion coefficient or the welding speed is too slow.
  • Incomplete Fusion: Insufficient laser power to fully melt the base metal or filler metal will result in incomplete fusion of the weld, resulting in a weak or incomplete joint.
  • Undercutting: Excessive melting of the base material can cause grooves or nicks at the edge of the weld, weakening the strength of the joint.
  • Warping: Laser welding generates a lot of heat, causing the welding material to expand and contract. This can cause deformation or warping of the welded material, which can affect the dimensional accuracy and quality of the product, especially for thin or fragile materials.
  • Oxidation: Exposure to oxygen during laser welding can cause oxidation of the base material, resulting in weakened joints and reduced corrosion resistance.
  • Sensitivity To Joint Assembly: Laser welding requires precise alignment of the two parts being welded. Any misalignment or variation in gap dimensions will affect weld quality.

To minimize these defects, laser welding process parameters, including laser power, welding speed, and beam focus, must be optimized and suitable filler materials and shielding gases used. In addition, proper surface treatment, joint design, and post-weld heat treatment can also help reduce the occurrence of laser welding defects.

Summarize

Laser welding is used for high-precision welding and since it does not use any electrodes, the final welding result will be light but strong. The initial investment is expensive, but the quality and characteristics of laser welding cannot be easily replicated. As lasers become more powerful and energy efficient, the future of laser welding looks bright!
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