What is a laser?

A laser is a device that produces a powerful and focused beam of light in a narrow spectrum of light. The word "laser" is an abbreviation for "Light Amplification by Stimulated Emission of Radiation". Simply put, a laser device gradually amplifies light of selected frequencies, thereby creating a special light. Compared to normally scattered light, this light can transmit large amounts of energy over longer distances. This property is used in many industries and also in welding.

Comparison with traditional welding methods

Laser welding offers many advantages over traditional welding methods such as TIG (Tungsten Inert Gas), MIG/MAG (Metal Inert Gas/Metal Active Gas) and MMA (Manual Metal Arc). Laser welding differs from traditional methods in that it does not use an electric arc to generate heat, but a high-energy light beam.

Laser welding is much faster and more efficient. Even inexperienced welders can achieve very strong and aesthetically pleasing welds in a very short time. After welding, there is no need to clean the welds with grinding or chemical processes. This means that laser welding eliminates some steps, which increases efficiency and reduces the cost of welders and consumables.

Laser welding offers the advantage of a good weld width to depth ratio. It can heat the material to a great depth even with a narrow weld. The heat affected zone is therefore smaller - and the subsequent deformation of the material is also smaller.

Laser welding can also be performed contactless and from a distance, which is an advantage for welding in hard-to-reach places. The rapid hardening of the material allows welding in various positions.

Advantages and disadvantages of laser welding

Laser welding offers many advantages, but there are also disadvantages that need to be considered.

- Advantages:

• High welding speed and efficiency.
• It creates strong and aesthetically pleasing welds.
• No additional grinding and cleaning of welds is required.
• Deeper penetration with smaller heat affected zone
• Possibility of contactless welding.
• Fast hardening of the material, which allows welding in various positions.

- Disadvantages:

• Greater demands on precision in preparing welded parts so that gaps do not form.
• Higher initial investment in laser equipment.
• Higher safety requirements due to dangerous radiation

The principle of laser welding - heating thanks to energy

Laser welding is the process of joining two materials by emitting a powerful beam of light. The laser beam is focused on a small area of the material's surface, creating a very high temperature.

When the laser interacts with the surface, the material reflects part of the laser beam. Part of the beam is absorbed by the material and converted into thermal energy (this is why, for example, higher power is needed when welding highly reflective materials). This causes the material to melt and then cool and crystallize, creating a welded joint.

When the laser hits the surface of the material, the material begins to heat up, melt, and vaporize. As the temperature changes, the reflectivity of the material also changes. (The higher the temperature, the lower the reflectivity.) The material also begins to vaporize, creating a “pit” and allowing the laser beam to penetrate deeper. As the laser beam continues to shine, the pits deepen. When the laser stops shining, the molten metal around the pit flows back and, after cooling and solidifying, the two welds are joined together.

Materials that can be welded by laser welding

A laser welder is used for very precise and fast welding of metal and thermoplastic materials, often for welding thin materials, sensitive and difficult-to-weld metals that are not easy to weld with arc methods.

Laser welding can be used on a wide range of materials. These include structural steels, alloy steels, duplex, Cr/Ni, high-strength low-alloy steels, carbon steels, refractory metals, chemically active metals, aluminum, titanium, nickel, magnesium and even copper, brass, silver and gold. Laser welding is also suitable for materials with high electrical and thermal conductivity, as well as for electrically non-conductive materials and materials with different physical properties.

Laser welding without filler material, but also with it

Laser welding provides the possibility of welding without additional material.

• Filler Welding: In this type of welding, additional material in the form of wire is added to the area being joined. This filler material helps to fill the gap between the materials and creates a strong weld. An example would be a fillet weld of thicker material on the inside.

• Fillerless welding: In fillerless welding, materials are joined directly without the use of additional material. This process is ideal for thin materials and allows for the creation of precise and fine welds. An example of this is the external fillet weld of thin sheet metal.

Laser welding safety precautions

Safety in laser welding is essential! When working with a laser, especially with laser welders, it is important to follow protective measures. Laser welders belong to the highest class of laser, class 4, where there is a risk of irreversible damage to the retina in the eye and skin burns.

To protect your eyes, it is therefore necessary to use special glasses designed for working with lasers that filter the relevant spectrum, or a welding helmet with a built-in filter.

Protective workwear is also important for skin protection. Safety is key, which is why laser welding is performed in the workplace, which protects people and flammable materials from the reflected beam.

Types of laser welders by radiation source

Based on the source of laser radiation, we distinguish 3 types of lasers:

• gas CO2 lasers
• solid-state Nd:YAG lasers
• fiber lasers

CO2 gas lasers

Gas lasers are lasers that use gases as the active substance to create the laser beam. CO2 lasers are probably the best known gas lasers and are mainly used for laser marking, laser cutting and laser welding.

Solid-state Nd:YAG laser welding machines

Nd:YAG lasers use a solid (crystal or glass) mixed with a rare earth element (neodymium, chromium, erbium, thulium or ytterbium) as a source of optical amplification. Nd:YAG lasers generate a beam by passing light through YAG (yttrium aluminium garnet) single crystals activated by neodymium (Nd) ions. The Nd:YAG laser can be pulsed or operated continuously.

The most famous solid-state laser is the ruby laser, which uses a synthetic ruby crystal - it is the first functional laser ever constructed. The Nd:YAG laser is commonly used in materials processing applications - e.g. engraving, etching, marking various metals and plastics, or for metal surface enhancement processes such as laser cleaning, cutting, welding.

Fiber laser welding machines

A fiber laser is a special type of solid-state laser that is a separate category. In fiber lasers, the gain medium is an optical fiber (quartz glass) doped with a rare earth element.

This type of laser differs precisely in the properties of the optical fiber to guide light: the laser beam is more direct and smaller than in other types of lasers, which makes it more precise. Fiber lasers are also known for their small footprint, good electrical efficiency, low maintenance and low operating costs. They are used in many applications, including material processing (e.g. laser cleaning, texturing, cutting, welding, marking), but also in medicine and the weapons industry.

Types of laser welders by operating mode

If we were to look at the operating mode of laser welders, all types of lasers can operate in one of two ways - their laser beams can be either pulsed or continuous.

• With continuous lasers, there is a constant flow of energy, which means that the laser continuously emits one uninterrupted laser beam.
• In pulsed lasers, the laser beam is interrupted at regular intervals to build up energy and achieve a higher peak power than in continuous lasers. The laser beam is released in the form of pulses that have a specific duration called the pulse width.

Is laser technology the future of welding?

Laser welding is a modern and efficient method of joining materials. Compared to traditional welding methods, it offers advantages such as speed, weld strength and reduced grinding requirements. Although it has some limitations, laser welding is an invaluable tool in many industries where joining materials with high precision and quality is required.