Joining
technologies

Friction Welding

Friction Stir Welding (FSW)

Friction Stir Welding (FSW) technology is a solid state welding process where a non-consumable rotating tool (normally comprised of a shoulder and a probe) is pressed against the materials to be welded. The friction and deformation produced between the tool and the base materials increase the temperature, leading to a softening of the materials to be welded. The tool is traversed along the joint line so that, due to its rotation and specific design, it generates a plasticized material flow, producing a mixture that consolidates the joint in the solid state.

FSW welding is a mature technology, particularly for low melting point alloys (aluminium, magnesium, lead, etc.). FSW welding of aluminium alloys is governed by the ISO25239 standard. LORTEK has participated in the development of this standard as a nationally-acknowledged expert.

The main characteristics of FSW welding are:

  • Consistent and repetitive process resulting in excellent properties of the welded joints (high mechanical properties, low distortions, and low residual stresses).
  • No welding consumables (no filler materials, shielding gases).
  • Clean and energy-efficient process (in solid state without fumes, splashes, sparks, UV rays, etc.).
  • Possibility of achieving high productivity: Large thicknesses in 1 pass, or smaller thicknesses at high welding speed.
  • Possibility of welding non-weldable materials by fusion-solidification (no porosities, cracking, etc.).
  • Sufficiently rigid clamping fixtures and welding equipment are required to counteract the high loads generated during the process.

Friction Stir Spot Welding (FSSW)

This is the spot welding variant of FSW welding. The image below shows a sketch of the basic principles of the process:

The main characteristics of FSSW welding are:

  • Consistent and repetitive joint quality, normally with no need of surface preparation.
  • Clean and energy-efficient process (in solid state without fumes, splashes, sparks, UV rays, etc.).
  • Possibility of achieving high productivity (cycle times of 3 to 5 seconds).
  • Possibility of welding non-weldable materials by fusion-solidification (no porosities, cracking, etc.).
  • Sufficiently rigid clamping fixtures and welding equipment are required to counteract the high loads generated during the process.
  • Welding equipment and holding tools are sufficiently rigid to withstand the large stresses generated in the process.

FSSW welding is a mature technology, particularly for low melting point alloys (aluminium, magnesium, lead, etc.). FSSW welding of aluminium alloys is governed by the ISO18785 standard. LORTEK has participated in the development of this standard as a nationally-acknowledged expert.

Rotary Friction Welding

Rotary friction welding technology is a solid-state welding process where a rotating part is pressed against a static part. The friction generated at the interface of the parts raises the temperature until the material is softened and plasticized. The rotation of the rotating part is stopped, and the pressure increased, so the two parts are forged together, producing the joint in the solid state.

The main characteristics of rotary friction welding are:

  • Consistent and repetitive joint quality, normally with no need of surface preparation.
  • Possibility of achieving high productivity with highly automatic processes.
  • Possibility of producing joints with dissimilar materials (aluminium-copper, aluminium-steel…).
  • Clean and energy-efficient process (in solid state without fumes, splashes, sparks, UV rays, etc.).
  • Sufficiently rigid clamping fixtures and welding equipment are required to counteract the high loads generated during the process.

Other friction joining processes

LORTEK also has experience and collaborations in other technologies, such as:

  • Friction Surfacing.
  • Refill Friction Stir Spot Welding.
  • Friction Riveting.
  • Friction Bit Joining.

What we are currently working on

  • Development of FSW welding equipment for different industrial applications.
  • Development of FSW tools with optimized designs and long durability.
  • Development of rotary friction welding equipment for different industrial applications.
  • Development of automatic non-destructive inspection technologies and quality control of FSW joints (IR thermography).
  • Development of FSW welding data control and monitoring: Smart FSW processes.
  • Development of advanced rotary friction welding process control systems.
  • High speed FSW welding of aluminium extrusions (up to 4 m/min).
  • High speed FSW welding of parts made by aluminium casting (up to 2m/min).
  • FSW welding of dissimilar thicknesses, “Taylor Welded Blanks” (TWB).
  • FSW welding of high melting point alloys (thin Ti64 titanium – up to 0.8 mm).
  • FSW welding of high strength aluminium alloys – aeronautic grades:
    • New third generation Al-Cu-Li alloys for fuselage structures.
    • Thick 7XXX series alloys for wing-box structures, with important reduction of the buy-to-fly ratio.

Specific Equipment

LORTEK has 3 FSW equipments with different and complementary characteristics:

Specific machine for FSW (i-STIR PDS4)

  • 6 servo-controlled axes (X, Z, rotation, tilt, forge, and pin).
  • Worktable ~1800x1000x350 mm (1000 mm FSW working stroke in X).
  • Servo-controlled hydraulic drives with axial force capability of up to 100kN.
  • Possibility of carrying out FSW welding processes in position control, force control or mixed control.
  • Test-Star TM advanced controller with high speed process control capacity and FSW welding data recording + monitoring.
  • Hydraulic spindle with ±3000 rpm rotation capacity and torque up to 180 Nm.
  • Spindle-mountable reducer with ± 800 rpm rotation capacity and torque up to 900 Nm.
  • Mountable cooled spindle and portable chiller for FSW welding processes with high melting point alloys (steels, titanium, etc.).

Robotic equipment adapted for FSW welding

  • Modified KUKA KR500-3MT robot + KUKA KR C4 controller.
  • 8kN rated load axial force capability in continuous operation.
  • ACTEMIUM BP-6700 spindle, specific for FSW welding.
  • Rotation capacity of ±3000 rpm and torque up to 32 Nm.
  • Worktable ~2500x2000x1000 mm.
  • Possibility of carrying out FSW welding processes in position control, or force control.
  • Advanced control software “FSW welding cell supervisor” with FSW welding data recording and monitoring capability.

CNC milling machine with adapted spindle for FSW welding

  • TWINHORN VP1500 CNC milling machine with 4 servo-controlled axes (X, Y, Z, rotation).
  • Worktable ~1500x600x600 mm.
  • 6kN rated load axial force capability in continuous operation.
  • STIRWELD spindle, version 3.2. specific for FSW welding with capability to carry out the process in force control.
  • “StirWelding Monitoring” process control software with axial force recording and monitoring capability.

Stock of FSW tools developed for different thicknesses and base materials

  • Thicknesses: 1-20 mm thick.
  • Tool material: M42, H13, WC-Co, W-25Re.
  • For specific application cases, LORTEK also offers the capability to manufacture new tools with specific designs according to the proposed application.

Publications and downloads

Publications
2008
Echeverría, A.A.M. da Silva, P. Alvarez, E. Aldanondo
Efectos de Ciclos Térmicos en las Propiedades Mecánicas de la Aleación de Aluminio 6082-T6 en Uniones por Friction Stir Welding.
In: X Congreso Nacional de Materiales, San Sebastián, Spain, 18–20 June 2008.
2010
E. Aldanondo, A.A.M. da Silva, P. Alvarez, A. Echeverría
Dissimilar Joining of AA1050 Aluminium Alloy and DP600 and Hot-Stamped Boron Steels using Friction Stir and Friction Stir Spot Welding.
8th International FSW Symposium, Timmendorfer Strand, Germany, 10–20 May 2010.
2010
A.A.M. da Silva, E. Aldanondo, A. Echeverría, P. Alvarez, E. Arruti
Friction Stir Spot Welding of AA1050 Al Alloy and hot stamped boron steel (22MnB5).
Sci Technol Weld Joining, 15 (2010), 682-687.
2010
P. Alvarez, G. Janeiro, A.A.M. da Silva, E. Aldanondo, A. Echeverría
Material flow and mixing patterns during dissimilar FSW.
Sci Technol Weld Joining, 15 (2010), 648-653.
2011
A.A.M. da Silva, E. Aldanondo, A. Echeverría, P. Alvarez, M. Eiersebner
Mechanical and Microstructural Investigation of Dissimilar Resistance and Friction Stir Spot Welds in AA5754-H22 and AA6082-T6 Al Alloys and 22MnB5 Hot-Stamped Boron Steel. Proceedings of Friction Stir Welding and Processing VI.
140th TMS Annual Meeting, San Diego, USA, February 27-March 3, 2011.
2014
E. Aldanondo, E. Arruti, A. Ormaetxea, A. Echeverría
T-joints in Aluminium alloys: Stiffened panels by FSW.
10th International FSW Symposium, Beijing, China, 20–22 May 2014.
2016
C. Leitao, E. Aldanondo, E. Arruti, D.M. Rodrigues
Aluminium-steel lap joining by multipass Fiction Stir Welding.
Materials and Design, 106 (2016), 153-160.
2018
M. Balakrishnan, C. Leitao, E. Aldanondo, E. Arruti, D.M. Rodrigues
Influence of pin imperfections on the tensile and fatigue behaviour of AA7075-T6 friction stir lap welds.
The International Journal of Advanced Manufacturing Technology, 97 (2018), 3129-3139.
2019
E. Aldanondo, E. Arruti, A. Echeverría, I. Hurtado
Friction Stir Welding of lap joints using new Al-Li alloys for stringer-skin joints in Friction Stir Welding and Processing X.
77–88, Febr 2019.

Success Cases

Development and industrialization of Ad-Hoc FSW equipment

Challenge

Industrial implementation of FSW to replace arc welding and flame welding.

Solution

Ad-Hoc FSW equipment, including development of controller with process data recording and monitoring capabilities, FSW tools, process parameters and ISO25239-based qualification, clamping and positioning fixtures, etc. Improvement of welded joint quality. Reduction of cycle time by approximately 80%. Reduction of manufacturing and energy consumption costs. Improvement of work environment and health of operators. LORTEK’s own control system (Copyright “SOFTWARE DE CONTROL FSW” - TXu 2-023-714).

Manufacturing of aluminium structures by T-joints and FSW welding.

Challenge

Reduce distortions in reinforced structures manufactured in aluminium by arc welding (MIG).

Solution

FSW welding in T-joints, including development of FSW tools, process parameters, clamping and positioning fixtures, etc. Up to 90% reduction of distortions; reduction of manufacturing times and costs.

Manufacturing of dissimilar structure of aluminium and steel by FSW welding

Challenge

Need to lighten the weight of structures by welding aluminium and steel components.

Solution

Design of structure to be manufactured by means of explosion welded, arc welded and FSW bimetallic materials. Development of FSW welding process, including FSW tools, process parameters, etc.

Partners or strategic alliances

Work carried out in collaboration with CAF R&D in the BIMETAL project. Publication of co-patent “METHOD FOR WELDING TOGETHER DISSIMILAR PARTS” (EP 3 178 600 A1).

Development of temperature measurement system for the FSW process

Challenge

Need to measure maximum temperatures reached during FSW processes.

Solution

Development of wireless temperature measurement system by means of thermocouples placed into the actual FSW rotating tool, with maximum temperature measurement capacity during the FSW process at the interface between the FSW tool and welded material. Patent publication application “Sistema para la medición de temperaturas en un procedimiento de soldadura por fricción – agitación” (PCT/ES2017/070807). Patent Publication Application: "System for the measurement of temperatures in a friction-agitation welding procedure" (PCT / ES2017 / 070807).

Partners or strategic alliances

System developed in cooperation with the University of Bordeaux within the framework of the MONITEMP project.

Development of FSW process control software for robotic equipment

Challenge

Need to optimize the FSW process control software for robotic equipment.

Solution

Control software developed with high-speed FSW welding process data acquisition and monitoring capacities. Improvement of stability and repetitiveness of FSW welding process in KUKA KR500-3MT robotic equipment.

Partners or strategic alliances

Software developed in cooperation with ACTEMIUM and optimized by LORTEK within the framework of the MALGUROB project.

Manufacture of stiffened structural panels by FSW

Challenge

Need to lighten the weight of structures for transport vehicles (automobile, aircraft, railway).

Solution

Development of FSW and FSSW processes for manufacturing stiffened structures with extrusions and rolled sheets welded in the overlap configuration. Improvement of dimensional quality (reduction of distortions compared with other welding processes) and structure stiffness/weight ratio. Reduction of manufacturing times and costs.

Partners or strategic alliances

Technologies currently under development within the framework of the ecoTECH project, in collaboration with Hellenic Aerospace Industry (HAI), Israel Aerospace Industries (IAI), AeroMagnesium (AM), AkzoNobel, NLR, ALTRAN, etc.

Development of FSW process for high-speed extrusion welding

Challenge

Need for high speed FSW (>3m/min), complying with the quality demands to respond to the manufacturing cycle times of the automobile sector (e-mobility).

Solution

High-speed FSW (up to 4 m/min) complying with quality requirements established by the ISO25239 standard, including development of FSW tools, process parameters, clamping and positioning fixtures, etc. Significant reduction of distortions and manufacturing costs compared with other welding processes.

Challenges

Challenges to be faced in the coming years:

Process industrialization by means of Ad-Hoc FSW, FSSW and Rotary Friction Welding equipment.
Automated manufacturing of large series (electric vehicle sector).
Shift of processes towards digitalization and industry 4.0:
  • Advanced process control systems (high-speed communications, temperature control, etc.).
  • Automatic non-destructive inspection and quality control technologies for FSW welded joints (IR thermography, artificial vision).
  • Data analysis and Machine Learning.
Process development for innovative materials and applications (high-speed welding, Al-Cu-Li alloys, Ti64, dissimilar thicknesses, dissimilar materials, etc.).

Egoitz Aldanondo

Main Researcher in Friction Welding

Mechanical Engineer specialized in Material Science by Mondragon Unibertsitatea, MSc Nanoelectronics & Mechanics - University of Sheffield, and MSc International Welding Engineer – CESOL. He joined the Joining Processes area of LORTEK in 2005, where he has mainly worked on the research and development of solid-state joining processes, such as friction welding and flash butt welding processes. Specialized in Friction Stir Welding (FSW) technology, he is the owner of 3 patents with more than 30 scientific publications in international journals and congresses. He is currently senior researcher in the Joining Processes area of LORTEK where he has participated in many research projects. He has also participated in FSW technology transfer and industrialization projects.