Hybrid LASER-Arc Welding Processes (HLAW): Bringing Together the Advantages of LASER and Arc








Do you know the effects of the hybridization of a welding process and its influences on the productivity and quality of the weld?








  In the late 1970s, Steen W. et al. first introduced the hybrid LASER-arc welding (HLAW) processes. His studies, carried out at the Imperial College of London, clearly showed the advantages of combining a LASER beam with an electric arc for welding.


  Through technological advances in the manufacture of high power LASER sources, and instruments that made it easier to understand what actually happens during the HLAW process, the emergence of a new and promising area of hybrid welding was possible. Among these, the LASER-GMAW hybrid welding process stands out. Similar to other engineering areas, welding processes have advantages and limitations. Through the performance of the two heat sources in the same melting pool, the HLAW process comprises the combination of the advantages of the two individual processes, making it extremely competitive industrially.


  Learn the advantages and limitations of the individual processes involved:


 The GMAW welding process is highly widespread in the academic and industrial environment, being perhaps the most representative among the electric arc welding processes, generating the joining through an arc that heats the metals to their melting point. The GMAW welding process offers several advantages over other welding processes. Among these, one can mention the low relative cost of the welding equipment, especially when compared to the LASER welding system. The process is considered to be simple to operate, not requiring a high level of operator experience to carry out manual procedures, but also offering ease of mechanization or automation. The process, as it depends on the addition material supplied in a roll, can be considered as independent of stops for changing the material, which supports its high productivity characteristic when compared to processes using limited size addition materials, as is the case of the SMAW process. Using advanced GMAW process modalities, it is possible to achieve metallurgical results applicable from joining, coating procedures, to applications in additive manufacturing. When compared to the LASER welding process, the main limitations are the low welding speed and, mainly, the low relationship between penetration and the width of the bead reached, since to make the joining of thick plates, it is necessary to pre-chamfering operation, and subsequently filling it with the addition material in successive layers, generating greater cost both in process time and in filler material.


  LASER material processing technology has been the target of major innovations in recent decades. The intensity of the heat source produced by the LASER beam is one of the most important aspects of the process, and justifies its use in several applications. When compared to traditional welding processes, this difference is clear and the consequence in the ratio of penetration / bead width achieved by the different processes, sent by the attainable levels of the intensity of the heat sources.


 The LASER welding process offers several advantages over conventional arc welding technologies. The ability to perform deep penetration welds with the keyhole mode makes it possible to weld extremely thick substrates with a single weld pass, thus presenting fewer opportunities for defects, in addition to removing the need for joint chamfering.


 In other hand, the equipment required for LASER welding requires a significantly higher investment than conventional arc welding equipment, in addition to presenting discontinuities such as porosity, humpings, and spatter when performed in the keyhole mode. In addition to these, due to the high thermal density of the process, the appearance of microstructures with greater hardness is favored in this process, enabling the development of mechanisms of crack formation during the life of the equipment.

  In welding applications for joining thick sheets and tubes, conventional arc welding processes are commonly used, such as GTAW (Gas Tungsten Arc Welding), GMAW (Gas Metal Arc Welding), SMAW (Shielded Metal Arc Welding) and SAW (Submerged Arc Welding). Depending on the thickness of the joint to be welded, it is necessary to chamfer it before welding, followed by several filling passes, thus guaranteeing the metallurgical union in all its thickness. The machining operation of the chamfer, added to the necessary number of necessary weld beads, directly imply in the longer manufacturing time, as well as greater consumption of materials.

  In this scenario, welding processes that enable high penetration remove the need for prior chamfering, thereby speeding up the entire production cycle. The LASER-GMAW hybrid welding process appears as a promising option for welding thick structures, ensuring high penetration and deposition rate, helping in the increasing geometric tolerance and reducing the need for joint chamfering, in addition to presenting metallurgical advantages, making it extremely interesting for industrial application.


  However, due to the high number of parameters involved and the complex interaction between the electric arc and the LASER beam, this process becomes relatively complex to be parameterized when compared to individual processes.


  The HLAW process has been used in the welding of a wide variety of metals, including ferrous metals such as carbon steel and stainless steel, and non-ferrous metals such as aluminum, magnesium, nickel, titanium alloys, etc. Currently, several countries are investing significantly in research and development of HLAW welding processes, with expressive results mainly in the automotive and shipbuilding industry.




References:

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