Manufacturers use different fabrication technologies, such as laser welding, to join materials in various applications. Laser beam welding techniques offer high welding speed, low thermal stress, and precise control compared to traditional welding techniques.
This article discusses the laser welding process, its types, working principles, and compatible materials. Let’s dive in!
What is Laser Welding?
Laser welding is a versatile fabrication technique that uses a laser beam to weld or join different metals and composites. Laser beam welding is the advanced sheet metal welding process commonly used across industries.
The laser beam is usually focused on the workpiece, heating it to a melting point. The welded material fuses with the adjacent material forming a solid joint. This process’s concentrated light energy focuses on very small spot sizes or areas, enabling precise control of the thermal energy and welding process.
How Does Laser Welding Work?
First, the laser beam welding machine focuses a highly concentrated light beam on the cavity between two or more materials to create a firm bond. This light concentration occurs at a small spot and ranges from a few tenths of a millimeter to a few millimeters in diameter.
This high-power laser beam concentration contains a high power density. As a result, it delivers massive energy levels that melt the materials at their closures or seams, making it a joint.
Then, the workpiece’s material gradually absorbs the energy from the focused laser beam, heating the workpiece to its melting point. Next, the melted region fuses to form a firm bond between the weld parts.
However, depending on the desired weld quality and welded material, you can perform laser welding in continuous or pulsed mode. Laser welding in continuous mode is ideal for welding thicker materials, while the pulsed mode suits thinner materials.
Types of Laser Welding Processes
While mig and tig welding are popular methods, there are several laser welding techniques that are useful for different applications. They include the following:
1. Keyhole Welding
Keyhole welding involves using a laser beam that heats the workpiece’s surface to the point of vaporization, infiltrating deeply into the material. This welding process forms a keyhole with a plasma-like feature. This welding technique is suitable with a high-power laser beyond 105W/mm2, and the temperature often rises above 10,000k.
2. Laser Brazing
The laser brazing technique involves concurrently using a laser beam to heat a workpiece with the filler material. This process forms a firm bond between the materials using filler materials like copper or silver. It is suitable for joining two dissimilar metals.
In addition, low-temperature brazing makes the welded material less susceptible to distortion. Industries such as automotive use laser brazing to join steel with aluminum.
3. Hybrid Welding
This welding technique joins laser beam welding with other methods, such as GTAW (Gas Tungsten Arc Welding) and GMAW (Gas Metal Arc Welding). This ultimately enhances the welding quality and efficiency of the technique by delivering the combined advantages of both methods.
4. Heat Conduction Welding
This process uses a laser beam that heats the material surface beyond the material’s melting point. It is an ideal welding technique for applications where high weld strength is not a primary requirement. The heat conduction welding process uses a low-power laser precisely below 500W. It creates a regular and aesthetically appealing weld.
5. Percussion Welding
Percussion welding involves pulsing the laser beam at a high frequency to melt and fuse the welded materials quickly. This welding method suits materials with varying melting points and thermal properties. In addition, it is perfect for joining dissimilar materials like aluminum and steel.
What Materials Can Be Joined with Laser Welding?
The laser beam welding techniques are versatile and compatible with various materials. Here are some of the typical materials joined with laser welding:
- Different aluminum alloy grades;
- Copper alloys such as bronze and brass;
- Steel variants such as high-strength alloys, carbon steel, and stainless steel;
- Titanium alloys are commonly used in medical and aerospace applications;
- Nickel and its alloys are used in applications including power generation and aerospace.
Laser welding applies to specific plastic types like thermoplastics that can melt and solidify repeatedly.
- Acrylic (PMMA): Its common uses include displays, signage, and medical equipment.
- Polyvinyl Chloride (PVC): PVC has common uses in medical applications, construction materials, and pipes.
- Polycarbonate (PC): It is widely used for automotive components, safety equipment, and electrical enclosures.
It joins composites of varying constituents, such as glass fiber-reinforced polymers (GFRP) or carbon fiber-reinforced polymers (CFRP).
Components of Laser Welding Equipment
Generally, standard laser welding equipment consists of the following essential components.
- Laser Source: This is a crucial component responsible for laser beam generation. Different laser sources include fiber, CO2, and Nd: YAG lasers.
- Beam Delivery System: It comprises mirrors and lenses that direct and concentrate the welding laser beam on the material. A typical beam delivery system is paired to a CNC system or fixed to a robotic arm.
- Cooling System: The cooling system maintains a stable temperature within the laser beam machine. It prevents the laser source and other components from damage due to the significant amount of heat that the laser generates.
- Workpiece Manipulation System: This system holds the workpiece steady, ensuring the beam creates the required specifications. It provides a stable and precise location for the welded workpiece.
- Safety Features: Welding materials together can be harmful when safety precautions are not in place. A laser beam welding system’s safety features include warning lights, interlocks, and shielding, which protects the operators and other personnel from the laser beam.
- Control and Monitoring Systems: These consist of software and hardware that manages the components of the laser beam system. These systems control and monitor different parameters, such as laser power and welding speed, during the welding operation.
Different Laser Machines Used for Welding
1. CO2 lasers
The gas or CO2 laser generates a laser beam with a carbon dioxide (CO2) laser. Manufacturers often employ CO2 lasers because they are efficient and create high-power beams suitable for fabricating thicker materials like plastics, ceramics, and metals.
2. Nd: YAG Laser Welding Machine
Neodymium-doped yttrium aluminum garnet (Nd: YAG) laser uses a solid-state beam in welding workpieces. It generates a high-quality beam suitable for welding thin materials like sheet metal and plastics.
3. Fiber Laser Machine
The fiber laser technique utilizes a fiber-optic cable to deliver the laser beam to the workpiece. Fiber lasers are efficient and can generate a high-quality beam perfect for welding metals and other materials.
4. Hand-Held Laser Welding Machine
This welding machine is a small, compact device that allows joint welding at various locations or angles. They are ideal for applications with mobility and accessibility to hard-to-reach area requirements.
5. Continuous Wave Laser Welding
Continuous wave laser welding machine employs a continuously emitting laser beam to form a continuous weld down the joint. It is ideal for creating high-quality and firm welds and welding thick materials.
6. Pulsed Lasers
The pulsed laser welding machine uses a laser beam produced at a high frequency and delivered at short pulses to make small and controlled welds. It is ideal for joining complex geometries and welding materials with varying thermal properties.
Advantages of Laser Welding
Laser welding is a versatile technique with several advantages in different applications. Here are some of the benefits of laser beam welding.
1. Reducel Thermal Impact
This welding process reduces the risk of thermal distortion in a workpiece since it uses less thermal stress at the weld seam. Laser welding minimizes the heat dispersed to the surrounding material, which could result in negative impacts such as bending or stress.
Laser beam welding is highly versatile and compatible with different thick plates, precious metals, copper contacts, or dissimilar metals. Its high compatibility with various applications makes it a commonly used sheet metal fabrication method.
3. High Speed
Laser welding techniques can weld up to 5 times faster or more than traditional processes. The high welding speed of this process results in shorter processing times and increased productivity within a limited time.
Laser welding techniques offer high reliability due to their force-free, non-contact, and wear-free attributes. Likewise, the process offers high strength because of its great welding depths.
Limitations of Laser Welding
1. High Initial Cost
Most laser beam welding equipment is expensive, making the process more costly than other welding techniques. The laser setups cost twice or more than the traditional welding systems. Therefore, it is expensive for low-volume applications and smaller productions.
2. Incompatible with Irregular Workpieces
Laser welding requires a direct line of contact between the laser beam and the joint being welded. Therefore, it is difficult to weld joints in irregularly shaped workpieces.
3. Special Skills and High Labor Costs Requirements
Laser welding techniques require specialized training and expertise to achieve excellent results. As such, it is challenging for smaller manufacturers to use due to its increased labor costs.
Factors Affecting the Laser Welding Process
Here are various factors that may influence the outcome of your laser welding operations.
Laser Power and Energy Density
The laser power directly influences the heat concentrated on the workpiece, determining the weld width and penetration. Generally, lower power levels cause insufficient fusion, while higher power levels allow deeper penetration. The power divided by the beam spot size is the energy density, which determines the density of the laser beam.
Beam Focus and Spot Size
The laser beam’s focus determines the spot size of the workpiece. Besides, deeper penetration and narrower welds occur due to the high energy density created by smaller spot sizes. The main length and spot size impact the shape of the weld bead and the energy dispensation.
The access to the welding area, geometry, and fit-up of the preferred joint’s design affects the process. Hence, the appropriate joint preparation helps to improve the weld’s penetration, quality, and strength.
It would help to know that a material’s thermal expansion coefficient, thermal conductivity, and melting point can impact its welding, influencing parameters like weld quality, speed, and power requirements. Furthermore, materials’ reflectivity and absorption properties vary upon exposure to laser radiation.
Applications of Laser Welding in Metal Fabrication
The automotive sector relies on the laser welding process for its cost-effectiveness, quality, and efficiency. It operates in a tool-free mode and usually doesn’t need head replacements. Various automotive components such as engine parts, solenoids, fuel injectors, and air conditioning units are good examples of machining parts using laser welding.
The laser welding method offers the precision the aerospace industry requires in different applications, such as airframes and security metal detectors. Laser welding techniques join lightweight and complex structures made from aluminum, titanium, and other alloys. Welding in the aerospace sector helps to reduce aircraft weight by reducing the use of rivets.
Manufacturers in electronics depend on sheet metal cutting and laser welding techniques to create various advanced electronic equipment. Product designers adopt laser welding methods and utilize continuous wave, Dd: YAG, fiber, and pulse laser welders. The welding machines produce precision welds for tiny, advanced electrical components such as sensors, microelectronic components, circuit boards, specific transistors, and control units.
Jewelry and Watchmaking
The Jewelry industry employs laser welding to produce and repair products with complex and fragile designs. It joins precious metals like gold and platinum, minimizing discoloration and distortion. This industry uses a “free moving” welding concept, making the operation relatively easy and safe. The laser beam maintains a fixed position while the operator safely turns the jewelry, ring, or bracelets before the beam.
The laser welding technique is reliable and compatible with vast materials and applications. More importantly, it offers more desirable results than alternate welding methods. However, to determine the right laser welding technique for your products, it is advisable to consider the workpiece material and the preferred results.
WayKen offers a wide range of machining services, such as custom CNC milling, sheet metal fabrication, injection molding, and various surface treatments, to meet all your specific needs. With our advanced equipment and experienced technicians, we can deliver high-quality and precise welding solutions for your machined parts. Just contact us to get started with a new project!
Can I cut with a laser welder?
You can use a laser welder to easily cut and weld different sheet materials like aluminum, iron wire, stainless steel, and carbon steel.
What are the common gases used in laser welding processes?
Nitrogen, helium, and argon are the common shield gases used in laser beam welding operations.
Is the laser welding process costly to operate?
Although laser welders are more expensive than traditional welding tools and machines, they are more efficient and user-friendly than traditional machines.