Joining
technologies

Resistance Welding

The resistance welding technology is based on the formation of a welding spot or seam by the fusion and coalescence of two metallic surfaces. Contacting parts are joined by the heat obtained from resistance to eletric current and the application of pressure. Electric power sources are used to generate high intensity electrical currents (thousands of amperes) and electrodes through which that current flows.

Noteworthy advantages of this technology are high energy efficiency, low part deformation, remarkably high production rates, easy automation and absence of filler metal.

Most important resistance welding processes:

  • Resistance spot welding where electrodes are used to generate discrete welding spots. The electrodes can be placed linearly or in parallel. It is used for the lap welding of 0.5 to 3 mm thick plates.
  • Resistance seam welding where disc-shaped electrodes are used. These rotate while the material passes between them, giving rise to continuous welding.
  • Projection welding where one of the materials to be joined has projections before welding. The heat is concentrated on these projections, which enables thicker parts to be welded, or welding situated at shorter distances between welds. It is applied to weld studs, nuts and other components screwed into metal plates.
  • Flash welding where the gap between two metal pieces through which a current is passed, creates resistance and produces an arc and melts the material. When the pieces reach the proper temperature, they are pressed and forged together, achieving an effective joint between the ends of the parts.

What we are currently working on

  • Selection of weld head and source for different applications.
  • Optimization of the welding cycle parameters (squeeze, welding and forge pressure, current, welding time, number of cycles) for different applications. Definition of operating windows.
  • Optimization of the type andgeometry of electrodes to increase their lifetime.
  • Joints between dissimilar materials of different thicknesses and with coatings.
  • Welding of high yield stress steels
  • Weld quality assurance by real time data recording and analysis.
  • Weld inspection.
  • Prediction of the electrode lifetime based on data and artificial intelligence systems.
  • Development of self-regulated systems for the automatic adaptation of welding parameters to the conditions of each batch/part.

Specific Equipment

Access to direct energy (AC), high frequency inverter (HFDC) and linear DC power sources through collaboration with thrid parties.

Toroidal coils to measure intensity and calibrate welding equipment and installations.

Artificial vision systems to inspect welds.

Thermographic cameras to monitor resistance welding process and inspect welds.

Publications and downloads

Publications
07/2017
Muniategui, A., Hériz, B., Eciolaza, L., Ayuso, M., Iturrioz, A., Quintana, I., & Álvarez, P.
Spot welding monitoring system based on fuzzy classification and deep learning
n 2017 IEEE International Conference on Fuzzy Systems (FUZZ-IEEE) (pp. 1-6). IEEE.
Open link
07/2016
Muniategui, A., Eciolaza, L., Ayuso, M., Garmendia, M. J., & Álvarez, P.
Electrode degradation analysis in aluminium-based resistance spot welding process
n 2016 IEEE International Conference on Fuzzy Systems (FUZZ-IEEE) (pp. 394-400). IEEE.
Open link
2011
Da Silva, A.A.M., Aldanondo, E., Álvarez, P., Echeverría, A., Eiersebner, M.
Mechanical and microstructural investigation of dissimilar resistance and friction stir spot welds in AA5754-H22 and AA6082-T6 alloys and 22 MnB5 hot-stamped boron steel
140th Annual Meeting & Exhibition TMS, San Diego (USA)
Open link

Success Cases

Ensure quality in resistance spot joints on high production rate lines (1 part per second)

Challenge

Ensure quality in spot resistance joints on high production rates (1 piece per second).

Solution

Develop a system for the real time acquisition and analysis of welding data and images. Data correlation with welding quality.

Partners or strategic alliances

Collaboration with home appliances sector enterprise.

Resistance joint (projections) of high yield stress steels up to 1.2 mm thickness

Challenge

Resistance joint (projections) of high elastic limit steels up to 1.2 mm thickness.

Solution

Optimization of process parameters, determination of parameter window, and correlation of parameters with fracture modes in chisel testing.

Partners or strategic alliances

Collaboration with automotive sector company.

Resistance joining of battery pack connectors

Challenge

Resistance joining of battery pack connectors.

Solution

Resistance joining of connectors to cylindrical and prismatic battery terminals. Parameter optimization and temperature analysis to ensure cell integrity.

Partners or strategic alliances

Collaboration with energy and storage system sector company.

Flash butt welding of large steel structures – chain rings and links

Challenge

Flash welding of large steel structures – chain rings and links.

Solution

Process specifications, parameter optimization and analysis of machine performance and variables to ensure weld quality. Welding Non-destructive inspection.

Partners or strategic alliances

Collaboration with wind energy and maritime sector industrial enterprise.

Challenges

Challenges to be faced in the coming years:

Ensure welding quality and integrity in industrial environments and with changes in material supply conditions (cleaning, coating thickness, etc.).
Ensure a robust welding process, minimizing the electrode degradation effects.
Application to high elastic limit steels.
Use of artificial intelligence-based techniques for learning and automatic adjustment of welding equipments.

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.