Joining
technologies

Arc Welding

Joining technologies, and among them, welding processes, play a key role in engineering and are essential for the manufacture of components, since many of them have welded joints. The capacity to create mechanically resistant joints, whose properties do not degrade with time, is critical in many applications and must be taken into account in the design, production and inspection stages. These joints can be found both in large constructions (buildings, transport, fluid pipes, etc.) and in smaller ones (electronic devices, small components,...). That is why joining technologies are identified as key enabling technologies for the development of innovative and sustainable manufacturing processes.

Within this context, electric arc welding processes hold a relevant historical position. Intensely developed after World War I, they have reached our times as mature, but constantly evolving technologies, proving, throughout, their ability to adapt to industry’s changing demands. Nowadays, the high quality of arc welded joints together with the high productivity of these processes and a somewhat lower cost than other joining technologies, mean that the position of arc welding in the market is extremely competitive.

The energy source used in arc welding processes to melt the base material is an electric arc. This arc is established between an electrode, which may or may not be consumable, and the two parts of the base metal to be joined together. MIG/MAG (Metal Inert or Active Gas) is the most noteworthy process that applies consumable electrodes, while TIG (Tungsten Inert Gas) and PAW (Plasma Arc Welding) (see Figure 1) are the processes without consumable electrodes which are mostly employed. As outstanding innovative processes in the market, we can highlight variants of the traditional MIG/MAG process with controlled heat input, and greater stability of the electric arc, such as the Cold Metal Transfer (CMT) process, developed by the Austrian manufacturer, Fronius, or variants of the traditional TIG process, but with greater productivity, such as the ArcTIG, TIGger or TIGSpeed processes, developed by different welding equipment manufacturers.

Innovative solutions

Currently, the objective of developing innovative solutions in this field is to increase the productivity of traditional processes, and at the same time improve the quality of these welded joints. In parallel, it is also worthy to note the global trend towards the digitization and automation of the industrial processes or Industry 4.0, which is bursting into this field. This is currently affecting to every development in the field of arc welding processes. Overall, pursuing the same objectives mentioned above: increasing productivity, maintaining an excellent quality of the welded joint, and in addition, promoting the improved traceability and robustness of traditional processes.

More specifically, it is important to note that innovations and improvements in these processes, today, are geared towards:

  • Adapting traditional arc welding processes to the extensive variety of materials to be joined, including new materials such as lightweight titanium or aluminium alloys, nickel-based super alloys, or coated materials such as galvanized steel.
  • Addressing dissimilar joints between two metal alloys (e.g., steel joints with Al or Mg alloys, joints between melting alloys and casting alloys, etc.).
  • Increasing the range of thicknesses of the parts to be joined, considering the global trend towards light weighting and the introduction of new materials.

What we are currently working on

Lortek’s knowledge area in arc welding processes addresses basic and applied research topics geared towards industrial needs. Lortek also aims at transferring new knowledge and solutions towards the industrial fabric.

To achieve this goal, LORTEK currently focuses in the next specialization topics:

  • Study of innovative arc welding processes aimed at increasing productivity, improving the quality of the welded joints and/or reducing their cost compared with the traditional alternatives offered by the market.
    • Tandem or double electrode type processes.
    • Low heat input MIG/MAG processes.
    • High productivity TIG processes.

  • Monitoring of arc welding processes:
    • Acquisition, storage and visualization of electric and process variables in real time (voltage, intensity, wire speed, welding feed speed, gas flow, torch position, etc.).
    • On-line quality control by different sensors (high speed cameras, thermography, acoustic sensors, etc.).
    • Seam tracking.

  • Welding process control: adaptive control and real time control of the welding process.

  • Study of joining and repairing processes, overlay and hard facing processes by arc welding.

  • Metallurgy of the welded joints:
    • Metallurgical characterization of the welded joints.
    • Study of the weldability of metal alloys and dissimilar joints.
    • Study of hot and cold cracking phenomena and mechanisms, sensitization and embrittlement associated with welding.
    • Optimization of the corrosion behaviour of stainless-steel joints.
    • Study of post-welding heat treatments: microstructural evolution, and joint properties.
  • Assessment of the welded joint quality: defectology (i.e., porosity, cracking, lack of fusion, etc.). Destructive and non-destructive methods to assess arc welded joints.
  • Specific Equipment

    Arc welding pilot plant equipped with several flexible and adaptable robotized welding cells (different power sources, welding torches, KUKA, FANUC, ABB robots, external axes, etc.).

    The welding cells are available for basic and applied R&D activities and technology transfer activities, including the manufacture of prototypes.

    We offer to industry different technology transfer services:

    • Development and optimization of welding parameters for different processes.
    • Development of welding procedures.
    • Adaptability to different standards and regulations.
    • Joint design.
    • Selection of consumables.
    • Comparative studies of different welding processes and technologies. Selection.
    • Concept tests at laboratory scale, industrialization feasibility studies and its integration into the production chain.
    • Manufacture of the first demonstrator: product development, applying our knowledge and expertise in welding.

    Discover our specific equipment: (DROP-DOWN MENU)

    • 5 power sources that give access to a wide range of arc welding technologies: Fronius TPSi, Fronius Transpuls (2), EWM Activarc, SBI plasma arc.
    • 1 Fronius FLEXTRACK45 linear axis for longitudinal mechanized welding.
    • FANUC and ABB 6-axis robots + 2 additional external axes.
    • CAD/CAM software: SKM and RobotStudio.
    • Communications architecture developed to capture, store and display process variables.
    • Equipment available for process control: SERVO-ROBOT and SCANSONIC seam tracking sensors, infrared thermographic cameras, high-speed cameras, acoustic sensor, pyrometers, thermocouples, vision cameras, etc.

    Publications and downloads

    Publications
    2019
    P. Alvarez, L.Vazquez, N. Ruiz, P. Rodriguez, A. Magaña, A. Niklas, F. Santos.
    “Comparison of hot cracking susceptibility of TIG and laser beam welded alloy 718 by Varestraint testing”. Metals, 2019.

    Success Cases

    Arc welding process of galvanized formwork props

    Challenge

    The problem associated with the arc welding of galvanized components lies in the vaporization of the zinc, which occurs as a result of the high temperatures of the electric arc. When these vapours, which place high pressure on the coating-substrate interface, are not properly evacuated during the welding process, they remain trapped in the melt pool, forming surface discontinuities; in other words, defects in the form of pores. In addition to porosity, splashes are traditionally associated with welding of galvanized steels, and consequently, a low aesthetic quality. On the other hand, the residual contaminants of welding may affect corrosion resistance and interfere with the coating functions.

    Solution

    A comparative study has been conducted at Lortek to test different solutions available in the market for arc welding of galvanized steels, including different type of consumables (solid and tubular metal wires), protection gases, arc processes (low heat input processes such as LSC, PMC, CMT), process variables (current intensity, welding feed speed, etc.), coating layer characteristics, etc.

    Optimization of welding process of tubes made of new super duplex steel

    Challenge

    For the chemical industry, and more specifically in industrial plants engaged in the manufacture of fertilizers, it is a challenge to guarantee good properties in joints of duplex and super duplex steels used to manufacture pipelines. This is especially important when welding on site and when the welding is exposed to highly corrosive atmospheres. The main objective is to guarantee good mechanical properties, with an adequate strength and toughness ratio, together with good corrosion behaviour of both the welding and the heat affected zone, avoiding the formation of fragile intermetallic phases, and guaranteeing an adequate balance between austenite and ferrite phases.

    Solution

    Lortek contributed to this project to the design and development phase of the butt-welding process of tubes made of a new super duplex steel developed by the Basque company, TUBACEX. Lortek defined different actions to tackle the problem: * identification of the influence of the critical parameters: heat input and temperature between passes in the welding process of super duplex steel, and approval of both the automatic and manual TIG welding process. Figure 4 shows a detail of one of the welding.

    Challenges

    Challenges to be faced in the coming years:

    The market is currently demanding highly efficient arc welding processes, with high productivity, robustness and reliability, with the expectation of reaching excellent joint quality and less dependence on specialized manpower. In addition to these demands, industries have increasing pressure to reduce manufacturing costs, and are introducing new alloys, new combinations of materials, and thicknesses.

    To tackle these challenges, arc welding machine manufacturers are developing innovative processes based on advanced digital controls of the electric arc, establishing complex relationships between the main process variables. Geared towards specific industrial processes and sectors, they seek to increase the welding speed and deposition rate, to reduce heat input and to control the transfer of metal through the electric arc reducing splashes and improving overall quality of welds.

    On the other hand, the digitization of the processes and the mass generation of data enable novel approaches to the improve and control arc welding processes, based on the information captured, not known to us before.

    Lortek’s approach to face the described challenges is based on its Technological Surveillance and Competitive Intelligence systems, which identify and analyse the market trends, the opportunities and threats, continuously updating the technological breakthroughs and new competitive scenarios in this field. Based on its excellence in information management, Lortek aims to maintain a strategic position as technological collaborator of their industrial customers for the identification of solutions, the completion of pre-industrial studies and the support during industrial implementation for new arc welding processes.

    Pedro Álvarez, PhD.

    Main researcher in WAAM, Arc and Laser Joining Technologies.

    PhD in Science by the University of Navarra. He has been a researcher in the Processes area since 2007. He is currently leader of research projects related to advanced joining technologies, and additive manufacturing of metal components. He is specialized in metallurgy and weldability, welding technologies (arc, laser, resistance, friction-stir, cracking), cladding, and additive manufacturing processes. He has led different European projects (2) and participated in others as researcher (7). At a national level, he has participated in more than 60 basic research, and applied research and innovation projects with companies. He has participated in numerous international conferences related to additive manufacturing and joining technologies (more than 30) and he is the author of 29 indexed scientific articles which have been referred 356 times.

    He is a member of the Spanish AEN/CTN 14 Technical Standardization Committee.

    He is a LORTEK delegate on the European platforms, AM Platform and Joining Platform. He has good communication skills in Basque and English (CAE certificate), full commitment and passion for research, continuous learning and business development.

    He is teacher and coordinator International Welding Engineer course (IWE) and of the Master’s Degree in Industrial Additive Manufacturing (University of Mondragon).

    In November 2018, he received recognition from the Basque Government as top researcher for his research work and scientific-technological merit.