Welding processes are present in all sectors of industry and have been used for component manufacturing purposes since the 19th century, becoming an international industrial demand process already in the early 20th century with the onset of World War I.
The improvement of welding technology has been occurring exponentially and has drastically influenced the metallurgical and financial results of production. Currently, there are numerous arc welding processes used, and each one has adequate advantages and limitations for certain applications.
In the mid 20th century, laser process technology was in focus in several laboratories in the world, and its strands were developed molding it for the most different applications.
The equipment required for laser welding, in general lines, is composed of the following equipment:
Laser Source, characterized by the generation of energy, being the main ones: CO2 Laser, Fiber Laser and Crystals Laser;
Laser beam transport systems; differing for each type of Laser source;
Optical system of collimation and convergence of the laser beam;
CNC drive system for welding heads;
In the welding scenario, the Laser process arises with several advantages over the arc welding process, among which one can mention:
Small Heat Affected Zone (HAZ) formed and low distortion of the part;
High penetration, allowing the union of thick plates in a single pass;
High repeatability of the process;
Process without contact with the parts to be welded;
It is not influenced by magnetic fields;
Relative ease of welding different materials;
Possibility of welding non-metallic materials such as polymers and ceramics.
However, like all processes, Laser welding has some limitations that must be analyzed for the purpose, such as:
Low tolerance of geometric positioning of parts;
High reflectivity in materials such as aluminum and copper alloys;
High cost of equipment;
Difficulty of being implemented in the field due to safety aspects.
The intensity of the heat source produced by the Laser system is one of the most important aspects of the process, and justifies its use in several applications. When compared to the conventional welding processes, the difference is clear and the consequence in the ratio of penetration/width achieved by the different processes.
In laser welding, depending on the power density levels used, two levels can be achieved, thermal conduction welding, and deep penetration welding (known as the Keyhole).
In thermal conduction welding, the material is heated above its melting point by the energy supplied by the Laser, but without vaporization. The shape of the melting pool and the depth of the bead depend on the thermal conductivity, geometry and initial temperature of the part.
In deep penetration welding (Keyhole), the material is heated above its evaporation point. Due to the pressure and steam flow of metal generated, a vapor channel is established in the melting pool.
Deep penetration welding provides cord ratios of depth/width greater than 10:1, the material being completely melted in front of the channel and solidifying behind the keyhole.
With the objective of achieving the advantages of arc welding and Laser welding in a single joining procedure, there are researches in several laboratories around the world, such as in the Laboratory of Precision Mechanics of the Federal University of Santa Catarina (LMP UFSC) already in advanced levels of consolidation of hybrid welding processes, where a second source is applied in the same melt pool, increasing the robustness, efficiency and flexibility of application of the process.
Hybrid Laser – Arc Welding (HLAW) processes will be better addressed and discussed in an upcoming article.
POPRAWE, R.; Tailored Light 2; Springer-Verlag, 2011. ISBN 978-3-642-01236-5 READY, J.; FARSON, D. LIA Handbook of Laser Materials Processing, Laser Institute of America. Orlando, Fl, 2001. STEEN, W., M; MAZUMDER, J. Laser Material Processing. v. 4th Edition, 2010.