Category: Applications of Fiber Lasers

History of marking techniques

The technology of marking on items is regarded as one of the oldest, since our ancestors put various markings and engravings on rocks and bones half a million years ago. Today, marking techniques performed by modern fiber laser systems remain an essential aspect of a business.

Early developments in marking technology

The first pneumatic device for marking was designed in the U.S. in 1973. It allowed people to understand the importance and vital application of marking to a business, resulting in the fiber laser marking area. The first laser systems were used for marking and engraving on metal. They offered low energy transfer efficiency and had a huge size, which is why they were soon replaced by the diode-pumped laser technology for marking.

Advantages of modern fiber laser marking systems

The new laser system offers such benefits as compactness and efficiency over the previous generation, leading to its use in numerous scientific applications. This marking machine was also improved, and the fiber laser-sourced marking machine has appeared. The fiber laser technology is widely used for marking and personalization in most industries due to its accuracy, higher cost-performance ratio, and extensive application on sophisticated parts.

Marking non-metal products

Additionally, there are laser systems for marking non-metal products. For instance, CO2 fiber lasers can be used for these purposes. “The marking industry has been advancing with the enterprises and becoming one of the essential parts for companies, especially those in industrial and manufacturing areas”.

Benefits for businesses

All business sectors can take advantage of marking by fiber laser systems. For example, fiber laser technology provides high-quality marking that is considered to be the biggest benefit over other marking techniques. The laser beam has a smaller size than physical engraving; the laser system is controlled by a computer, significantly increasing the accuracy. Modern fiber laser systems for marking enable the production of complex forms, making small figures and text readable.

Product personalization and brand promotion

Fiber laser marking allows every business to make its product unique to increase sales and promote better brand recall and loyalty. CO2 fiber lasers for non-metal materials help engrave unique text, graphics, and barcodes to distinguish your products from others, since personalization plays a crucial role for businesses now.

Efficiency and durability of laser marking

The ability of fiber laser systems to penetrate and engrave is another great benefit of laser marking because they favor reducing not only time but also costs in manufacturing as well. The quality and durability are not lost during the process of laser system marking.

History and significance of laser technology

More than 40 years have passed since the development of the first laser system, but this was enough to make quantum electronics one of the leading areas of science and technology. Numerous improvements of lasers and their application make it possible to obtain fundamentally new results in information systems and communications, in biology and medicine, in space, and in other scientific research.

Unique properties of laser beam emission

Laser beam emission is characterized by monochromaticity, sharp focus, due to which it is possible to concentrate laser beam energy and power at considerable distances, the ability to vary the modes of radiation from continuous to pulsed with different pulse durations, and finally, coherence and polarization. A unique combination of these properties allows realizing various interaction mechanisms – both thermal (plasma formation, ablation, evaporation, melting, heating), and non-thermal (spectral resonance) effects on matter, which affect complex atomic and molecular systems.

Early adoption in medicine

It is not unexpected that the concept of employing laser beam radiation in medicine seems to be one of the initial. Over the past years, fiber laser devices and techniques have been used in almost all sections of medicine. Fiber lasers are especially successful in surgery, therapy, and the diagnosis of diseases. At the same time, it was discovered that each type of laser system operation, each laser-medical technique requires a specific combination of basic parameters of laser beam radiation and knowledge of the mechanisms of its interaction with various tissues.

Main areas of fiber laser application

Today, there are three main areas of fiber laser application in medicine.

Non-invasive diagnostics

New methods of non-invasive diagnostics: optical coherence tomography is considered to be a promising method for the diagnosis of ophthalmic and cancer diseases, and laser spectral analysis of biomarker molecules in exhaled air for diseases of the gastrointestinal tract. 

It is these diagnostics that use such unique properties of laser beam radiation as high coherence and polarization, which distinguish it from ordinary, even monochromatic, light.

Therapy using fiber laser systems

The therapy by fiber laser systems is widely used: irradiation with low-intensity laser systems of poorly healing wounds or human blood; in combination with photosensitizers, low-energy fiber lasers are used to selectively destroy cancer cells, atherosclerotic plaques, and treat macular degeneration (photodynamic therapy).

Surgical applications

Powerful (high-energy) laser systems are used as a surgical tool in ophthalmology, otorhinolaryngology, urology, and cosmetology. The surgery uses high-intensity laser systems that cause irreversible changes in tissues: welding, evaporation, and ablation (removal and cutting).

External and intravenous laser therapy

The therapy by fiber laser systems is another area that has become most widespread in the whole world – irradiation with low-energy lasers of blood and poorly healing wounds.

Mechanism of external laser therapy

For external use, laser system treatment occurs by exposure to certain areas and points of the body. The light penetrates through the tissues to a greater depth and stimulates the metabolism in the affected tissues, activates the healing and regeneration of wounds, and there is a general stimulation of the body as a whole.

Mechanism of intravenous laser therapy

During intravenous fiber laser system therapy, the laser beam influences the blood through a thin light guide that is inserted into a vein. The intravascular effect of low-intensity radiation allows you to affect the entire mass of blood. This leads to stimulation of hematopoiesis, strengthening immunity, increasing the transport function of blood, and also helps to increase metabolism. Significantly positive effects in laser system therapy of angina pectoris, myocardial infarction, and other pathologies were obtained with the introduction of an optical fiber through which laser beam radiation was introduced into the patient’s elbow vein.

Coherence and polarization considerations

Fiber laser radiation differs from ordinary, even monochromatic light by its coherence and polarization. There is a misconception that these special properties are responsible for the observed clinical and photobiological effects. As the laser beam penetrates deeper into the biological tissue (skin, organ, blood), coherence and polarization persist only to a depth of 200-300 microns, and then these properties disappear, and incoherent and non-polarized, monochromatic radiation spreads. Consequently, the beneficial effects observed during laser system therapy of various diseases are caused not by some special properties of fiber laser exposure, but are similar to the action of ordinary unpolarized and incoherent light with an appropriate radiation wavelength.

Secondary radiation and deeper effects

Photons emitted by electrons of excited biomolecules form secondary radiation that propagates (scatters) in all directions and excites other biological tissue molecules, increasing the depth of effective exposure. Due to the diversity of biomolecules in the body, secondary radiation is broadband, incoherent, and non-polarized.

Role of blood and lymph transport

Another factor that increases the depth of effective exposure is the transfer of excited molecules by blood and lymph throughout the body. It can be assumed that at depths exceeding 3 cm, the main biological effect is exerted not by the primary, laser beam radiation, but rather by the secondary scattered broadband incoherent and non-polarized radiation.

Challenges in dose determination

It is also very difficult to determine in practice the dose of absorbed laser beam radiation, since the proportion of reflected and absorbed radiation depends on many factors, so some researchers believe that fiber laser system therapy is an art like all medicine.

Mid-IR fiber laser applications

Today, two applications of fiber laser selective excitation of material vibrational levels in the mid-IR region of the spectrum are distinguished: fiber laser surgery of soft and hard tissues and laser system evaporation of polymers for thin-film spraying. These fiber laser system applications are based on the ability of mid-IR lasers to cause thermal or thermomechanical changes in the materials being processed, which can be classified as phase changes rather than laser beam chemistry. Fiber lasers have great potential for creating precision surgical instruments, due to their ability to focus laser beam radiation into a small spot along the length. A larger penetration depth increases the number of damaged cells, while a shorter depth results in less material removal per pulse.

Surgical precision and ablation

The goal of laser beam ablation is to remove a specific part of the tissue, leaving the surrounding tissue biologically alive. Surgical requirements, however, are often the opposite: high ablation rates are required in dentistry, while they should be minimal in refractive ophthalmology; cutting vascular tissues (brain surgery) requires some amount of surface coagulation (“thermal damage”) to achieve hemostasis (stop bleeding), while for non-vascular tissue (cosmetology) wound healing is better when there is no thermal damage.

Photodynamic therapy (PDT) with fiber lasers

Laser systems are finding new applications in PDT, a new cancer treatment method. Unsuccessful attempts to control the development of cancer remain a major problem. The main goal for patients with an incurable disease is to delay the development of the tumor. If the tumor is not large, the fiber laser system thermal ablation may become the treatment.

Mechanism and applications of PDT

Photodynamic therapy (PDT) by laser systems is another minimally invasive strategy for the removal of tumors. The idea behind PDT is to use the toxicity of porphyrin to destroy tumors. Up to the present moment, it has mainly been used to treat superficial, malignant, or pre-malignant lesions of the mucous membrane, carcinoma of the bladder, tumors of the esophagus or bronchus, a tumor on the head or neck, accessible through the endoscope. In combination with special catheters and the development of new photosensitizers, PDT by fiber laser systems can be effective for patients with solid tumors and especially with liver metastases.

Replacing traditional ultrasound imaging

Conventional ultrasound imaging has been substituted by a laser technology alternative that does not require physical contact and can be used on patients who cannot tolerate a probe on their skin, such as burn victims, individuals with sensitive skin, and infants. Tissue imaging has been conducted safely using a remote laser system aimed from half a meter. The laser technology was tested on the forearms of volunteers, resulting in high-quality images, comparable to the standard ultrasound, where common tissue features, such as muscle, fat, and bone, down to about 5 cm below the skin, were observable.

Challenges of laser-based imaging

Sound waves can penetrate further into the body than light; therefore, the primary challenge is converting a laser beam’s light into sound waves at the skin’s surface to visualize deeper within the body. 1550-nm lasers are used for tests because a laser beam wavelength is absorbed by water and is safe for the eye and skin with large safety margins.

Human skin consists largely of water, so researchers confirm that it should ideally absorb the wavelength of 1550-nm lasers and that it would heat up and expand in response. Then it is expected that the skin creates sound waves that spread through the body as the laser system’s wavelength returns to its standard state.

Dual-laser setup for imaging

One pulsed laser at 1550 nm that emits sound waves, and a second continuous laser system that remotely detects reflected sound waves, are used to test the idea. This second laser acts as a motion detector, allowing the measurement of vibrations at the skin surface. Skin surface motion, in its turn, changes the laser beam’s frequency. The 1550-nm laser system enables obtaining data at various points and creates an image of the region.

Testing and results

The first tests of the developed laser system include imaging of metal components installed in gelatin (similar to water in skin),  imaging of animal tissues, and then experiments in humans. Ultrasound scanning of forearms helps to develop the first fully non-contact laser system for safe tissue imaging. Additionally, the 1550-nm laser system allows a clear distinction of the fat, muscle, and tissue boundaries.

It is planned to improve the laser technology by increasing the laser system’s performance. Moreover, the researchers plan to update the detection laser beam’s abilities as well as to miniaturize the laser system setup up resulting in the manufacture of a portable imaging device that may be used at home.

The importance of space exploration

Space exploration remains highly relevant not only for companies specialized in it but also for ordinary enterprises. Space holds numerous secrets that are extremely hard to uncover, and this is the main reason why people are striving to be closer to it; consequently, they build observatories with large telescopes.

Today, the peak of Mount Wilson, California, is an important place for scientific research and the residence for numerous observatories. It has the world’s largest optical interferometer, CHARA. Now two more observatories are being built there, and the Facebook company plans to use them for their first laser communication systems, whose main goal is the connection to orbital satellites.

Athena satellite project

The company is working on an experimental satellite, Athena, that can provide efficient, fixed, and mobile broadband in areas with bad service. Facebook will utilize laser system technology both in Athe thena satellite and their future spacecraft. The Facebook company has long been interested in laser modules and communication systems in space because fiber laser systems allow transmitting more data at high rates, and their signals are protected from interference or hacking despite clouds.

How laser satellite communication works

Laser satellite installation includes the observatories with the aim of laser beam transmission into the atmosphere or a satellite to lock onto. This laser system installation will be useful for space mission applications, for satellite and aerospace industries, and Facebook’s mission of connectivity.

Laser system communication allows connecting the unconnected, and it is highly effective for people in hard-to-reach places to provide the Internet for them.

Key features of laser satellites

The Internet satellite includes near-infrared lasers that are eye-safe and have higher data rates than a traditional radio-frequency satellite, in spite of the fact that the fiber laser system is compact, lightweight, and high-power.

Regulatory aspects and opportunities for new companies

This type of satellite will be especially interesting for new companies because laser communication frequencies are not yet regulated. The use of a laser system satellite means that it won’t be necessary to track rapidly moving objects, for example, drones or satellites in low Earth orbit.

Even laser beams of high quality spread out and become weaker in thirty-six thousand kilometers travel long from a geosynchronous orbit. This technology still needs to be developed, but it is considered to be very promising.

The role of laser systems in modern life

Today, in the era of new technologies, it is very hard to imagine human life without the use of laser systems. Fiber lasers became an integral part of modern equipment and society as a whole. The fields of their application continue to enlarge and include not only physics, medicine, and other natural sciences, but also security.

Recently, a group of researchers from Massachusetts has developed a laser system-based technique of transmitting different audio signals and even recorded speech at a conversational volume to a person without any receiver equipment. The principle of the laser module device operation is based on the photoacoustic effect.

How the technology works

It is possible to transmit sound selectively due to the use of water vapor in the air, with the aim of light absorption and then the creation of a sound. The use of the laser system device is not limited to only wet conditions, but it is ideal for relatively dry conditions because the air always has a little amount of water, especially around people.
Also, the researchers found that it is not required to have a lot of water due to a laser wavelength that is highly absorbed by water. The stronger absorption leads to more sound. The laser system device creates an audio signal that is heard at a certain distance from the transmitter, enabling it to be localized to a certain person.

Basis of the development

The basis for the laser module development was a method called dynamic photoacoustic spectroscopy for chemical detection because sweeping a laser beam at the speed of sound could make chemical detection more precise. The main particularity of the method is that the audio signal can only be heard at a certain distance from the transmitter.
It means that an individual can get the message rather than a group of people crossing the light from the laser beam. The researchers confirm that there is a possibility of transmitting the message to multiple individuals. They also demonstrated the transmitting distance that is more than 2.5 meters away at 60 decibels using the laser system sweeping technique. In the future, the distance could be longer.

Accuracy and advantages of the method

The conventional photoacoustic technique provides sound with higher accuracy, whereas the laser beam sweeping provides sound with louder audio. The possibility of transmitting highly targeted audio signals over the air is considered to be quite useful for warning individuals of a dangerous situation, for example, during terrorist attacks. It is the first system that uses laser systems that are totally safe for the eyes and skin to localize an audible signal to a particular person.

Exploring the Moon’s south pole for water

The Moon always attracts people’s attention; it is fraught with many mysteries, which researchers try to reveal. There are craters in the south pole that have remained dark for billions of years; however, researchers claim that the region may include water. NASA encourages different research teams to create technologies to look for and extract water from these areas by using fiber laser technology.

Femtosats and laser technology

One group of researchers has proposed a technique based on the combination of laser beam power with femtosats (compact, disposable satellites) to look for water on Earth’s moon. “NASA selected eight university teams, including a joint team of researchers from the Colorado School of Mines and the University of Arizona, to develop fiber laser technology to support efforts to find and harvest water at the moon’s south pole.”

Laser-powered lunar exploration

Colorado School of Mines studies the concept of laser system application to power laser beam lights and machinery employed for lunar exploration. The researchers plan to apply femtosats, tiny satellites about the size of a stick of butter with laser systems, to verify the viability of using laser beam signals for power and communication in a lunar environment.

Advantages of compact satellites

The peculiarities of these compact satellites are that they are considered to have a low cost; therefore, it is possible to buy tens, hundreds, maybe even thousands for the price of one standard satellite. Insufficient research about the environment of the moon’s south pole led to the combination of the disposal spacecraft with a fiber laser is an ideal technique to examine these areas without risking hurt to a more expensive satellite.

Mission concept for lunar water search

The researchers proposed to conduct a mission in which is that a lander-mounted fiber laser system will land on the surface of the Moon and set the femtosats into action at various points on the lunar surface, applying a jack-in-the-box-like technique. The femtosatellites obtain the laser beam signal from the laser system and transmit it back to prove the validity of applying the fiber laser for communication.

Ultimately, the researchers are currently creating the complete fiber laser system, a task that is quite uncommon, especially in the aerospace sector. This mission is a step toward creating the required laser technologies to search for and extract water on the lunar surface.

Benefits of ultrafast fiber lasers

Ultrafast fiber laser systems provide two unique benefits that include the highest accuracy in material processing and the capability to process almost every material. Fiber lasers of average powers, up to approximately 100 W, are used for industrial applications, while laser systems of higher powers are more suitable for research.

Development of next-generation fiber lasers

Also, the popularity of fiber laser systems is growing. A team of researchers from Germany has developed the next generation of ultrafast laser systems with enough power to overcome standard lasers. Apart from the development of fiber lasers, it is planned to create process laser technology and the first applications as well.

Laser design and efficiency

The team consists of laser beam source development groups that work on complementary approaches to create a totally new fiber laser system. The new fiber laser is based on a decade-long experience with a special slab laser system design. The fiber laser is perfect for the generation of continuous-wave (CW) laser beam radiation efficiently with diode pumping.

High-power pulsed radiation

This laser system is considered to be a solution for the emission of pulsed and ultrashort-pulsed laser beam radiation. The present version is developed for 5 kW laser beam radiation with 800 fs pulses from two amplifier stages. The power radiation is planned to increase up to 10 kW by using a thin disk amplifier stage.

Coherent beam combination concept

The concept of a coherent combination of fiber laser beams has also been developed. According to the concept, “almost-identical fiber amplifiers are pumped by one seed laser system, and they then generate amplified laser beams in parallel. With optimal spatial and temporal overlap, these beams can be combined with 96% combining efficiency.” The fiber laser has already been tested and demonstrated 10.4 kW of compressed average power with 240 fs pulses.

Additionally, the researchers pay attention to process technology to promote the efficient application of such high powers, resulting in the development of high-speed polygon scanners that improve laser beam deflecting and splitting schemes. The process of splitting off a multikilowatt laser beam into arrays of more than 100 identical but shaped laser beamlets allows performing high-throughput micromachining.

Introduction to fiber laser material processing

Laser technology for material processing is currently experiencing the peak of its development and popularity. Modern fiber laser technologies are rapidly being introduced into industrial production and the advertising business, often replacing traditional methods of material processing.
The focused laser beam of adjustable power turned out to be an ideal “working tool” for the creators of new equipment. The laser system for cutting and marking, welding and surfacing, as a material processing tool, works quickly and does not wear out; it is economical, highly accurate, and its impact is easy to control and manage.

Advantages of fiber laser technologies

Laser  technologies for material processing have several advantages that contribute to the expansion of their application in various industries and services:

• a diverse selection of processed materials.
• no mechanical impact on the product with minimal thermal,
• precision and guaranteed repeatability,
• high contrast and durability of the images applied,
• high speed and performance, saving on consumables, and low power consumption,
• possibility of laser beam processing in hard-to-reach places, on flat and curved surfaces,
• the ability to integrate the fiber laser into various technological processes, including production lines and robotic systems.

Applications of fiber laser systems

Laser system engraving is effective for personalization of souvenirs and gifts, and fiber laser application for personal and greeting inscriptions. Laser beam cutting as a high-precision tool allows for the production of products with minimal material consumption and without additional processing of the cutting edges. Laser system welding is characterized by high welding speeds and high-quality welds with minimal weld sizes.

Laser hardening

A fiber laser or thermal hardening of metals and alloys by laser beam emission is based on local heating of a surface area under the influence of radiation and subsequent cooling of this surface area at a supercritical rate as a result of heat transfer to the inner layers of the metal.
In contrast to the known processes of thermal hardening by quenching with high-frequency currents, electric heating, melt quenching, and other methods, heating during laser beam hardening is not volumetric, but a surface process. At the same time, the heating time and cooling time are insignificant, and there is almost no exposure at the heating temperature. 
These conditions provide high rates of heating and cooling of the treated surface areas. Due to these features, the formation of the structure during laser beam heat treatment has its own specific features. The main purpose of fiber laser thermal hardening of steels, cast iron, and non-ferrous alloys is to increase the wear resistance of parts working under friction conditions. 
As a result of laser system hardening, high surface hardness, high dispersion of the structure, a decrease in the coefficient of friction, an increase in the bearing capacity of the surface layers, and other parameters are achieved. Fiber laser hardening provides the lowest wear and friction coefficient, and furnace quenching – the highest. 
Along with this, hardening by the fiber laser system is characterized by very small running time (only two or three cycles), a decrease in the upper values of the number of acoustic emission pulses, and a small interval of change in the number of laser beam pulses. This is due to an increase in the uniformity of the microstructure of the surface area after laser system hardening.
The wear resistance of cast iron and aluminum alloys under sliding friction conditions after continuous laser treatment is noticeably increased. The increased wear resistance of cast iron after laser beam treatment is due not only to the corresponding structural and phase composition but also to improved friction conditions. It also increases the wear resistance of steels and some other alloys when friction occurs in alkaline and acidic environments.

Laser system cutting

Fiber laser cutting is a laser technology that uses the energy of a laser beam to cut various materials. Laser cutting is usually used on industrial production lines. Technologically, this process is reduced to focusing a high-energy laser stream on the material being cut. The material, in turn, begins to melt, burn, evaporate, or be removed by a stream of auxiliary gas. 
The laser beam cut is characterized by high edge quality and positioning accuracy. Powerful industrial fiber lasers can cut metal sheets and other materials of various shapes with equal ease. Laser system cutting has a number of advantages over other metal-cutting methods. 
The advanced equipment of the fiber laser system cutting machine is able to process almost all metals and their alloys. It becomes possible to achieve a minimum area of the cut, while there is almost no deformation of the edges. The purchase of laser system cutting equipment is advisable in cases where it is necessary to perform the following types of work:

• Machine processing of metal without high initial costs and physical contact with the metal
• Metal processing without using a large amount of manual labor
• Metal cutting that does not involve further processing of the part
• High-speed metal cutting, which is accompanied by a slight thermal effect on the metal surface
• Cutting of finished products (past painting processes, etc.) without losing the external qualities of the part.

The fiber laser is able to operate in pulse-periodic and continuous modes. The technological capabilities of the laser beam equipment allow performing metal cutting operations that are accompanied by a small amount of waste. Since the laser system cutting machine is characterized by high positioning accuracy, it is possible to significantly reduce the cut tolerance, which leads to high economic efficiency of cutting. 
The laser beam of high quality makes it possible not only to cut metal with high precision but also to create holes in it with a diameter of 0.2 mm or more. The fiber laser system for cutting is characterized by a high speed of operation, which depends on the power of the laser beam.
Laser cutting equipment makes it possible to process non-rigid parts and parts that are easily subject to deformation. The use of laser technology enables cutting out details of any, even the most complex contour.

Laser engraving

Fiber laser engraving includes the removal of the surface layer of a material (metal, plastic, leather) or coating (paint, electroplating, spraying) under the influence of the laser beam of high quality. Laser system engraving will not be erased and will not fade. It can rightfully be called eternal. 
The laser beam process is controlled by a computer, which allows engraving images from any digital format (after the necessary processing). The laser beam of high quality allows applying high-resolution images. This makes it possible to engrave high-quality microimages and microtexts.
The laser beam modes embedded in the system can vary widely. This allows adjusting the depth of the burning of the material. For example, there is a deep engraving in metal for maximum clarity and durability, or evaporation of the top layer of paint for the product label without affecting the material itself.
In addition to the standard three-dimensional laser system engraving, there is a technology for obtaining color engraving. Colors in fiber laser engraving of metal are achieved due to the appearance of oxide films in the area of laser beam exposure. The laser technology for obtaining them is innovative and unique. The colors are selected separately for each new material.

Laser welding

Fiber laser welding is a welding technology used to attach various parts of metal using a laser system. Due to the high concentration of laser beam energy in the welding process, a small volume of molten metal, the small size of the heating spot, high rates of heating and cooling of the weld metal, and the near-weld zone are provided.
The process is often used to perform large volumes of production, such as in the automotive industry. Depending on the purpose, continuous or pulsed fiber laser operation can be used. A laser beam with a pulse time of the order of milliseconds is used for welding very thin workpieces. A continuous laser system is used for deep welding.
Fiber laser welding is a universal welding method that can be used to weld carbon steel, stainless steel, aluminum, and titanium. A high cooling rate can lead to thermal damage when welding carbon steels. The welding quality is high, similar to electron beam welding. The welding speed is proportional to the applied power and also depends on the type and thickness of the workpieces. 
The high power potential of fiber laser systems makes them particularly suitable for large production volumes. This type of welding is particularly dominant in the automated industry. Some of the advantages of fiber laser welding compared to conventional include: air route can be used to transmit the laser beam, that is, there is no need to vacuum, it is easy to synchronize manipulators, there is no X-ray radiation, and it provides the best quality of welds.
One of the methods of laser system welding is hybrid laser beam welding. This is a combination of laser and arc welding (gas metal arc welding). The electric arc melts the wire, ensuring a constant arc length, while the wire is fed automatically by the wire feeder. Protective gases (argon, helium, carbon dioxide, and their mixtures) are used to protect against the atmosphere that appears from the welding head, together with the electrode wire.