FSSW – Friction Stir Spot Welding

Friction Stir Spot Welding (FSSW)

Spot-welding technology for similar and dissimilar materials

FSSW – Functional principle

Friction Stir Spot Welding (FSSW) is a variant of friction stir welding. A rotating tool is pressed with high force into the top of two sheets that lie on top of each other in an overlap joint. The frictional heat and high pressure plasticize the material so that the tip of the pin plunges into the joining zone between the two sheets. The shoulder of the tool applies high forging pressure, which causes the components to metallurgically bond together without melting. The tool is usually only plunged into the sheets in the z-direction until the shoulder is in contact with the surface of the top sheet. After a short dwell time, the tool is pulled out of the workpieces again so that a weld spot can be created approximately.  

Friction stir spot welding is usually carried out with a console, or a robot. 

FSSW – Functional Principle

FSSW Applications

  • Car doors, tailgates, roof panels in Japanese passenger cars
  • Rolled aluminum sheet on extruded profiles for the aluminum doors on off-road vehicle
  • Pole connector between positive pole (aluminum) and negative pole (copper) for batteries
  • Highly dynamically loaded crash-relevant components
  • Aluminum-steel connections in lightweight automobile construction
  • Steel side impact protection in aluminum doors
  • Aluminum tabs on cast or forgings of Italian small cars
  • Extruded aluminum profiles on steel pipes in bus construction
  • Compounds of high-alloy chromium-nickel steel in lap joints
electron-microscopical view on Al-Fe interface

The advantages of Friction Stir Spot Welding

  • High joint strength
    FSW produces welds with excellent mechanical properties, due to no solidification and a forged, fine-grained microstructure.
  • Minimal distortion
    FSW operates at lower temperatures and low heat input compared to fusion welding, welded components have a reduced distortion and residual stress levels, ideal for welded parts with tight tolerances.
  • Excellent fatigue behavior
    FSW generates a fine-grained forged microstructure in the joint line, which lead to excellent fatigue properties.
  • Joining dissimilar materials
    FSW can join dissimilar materials due to the low heat input high forcing action, including different aluminum alloys, like wrought aluminum to aluminum cast or aluminum to steel or copper, and even advanced composites.
  • Environmentally friendly
    FSW produces no fumes, gases, or radiation; no protective gas, additional material or preparation of the joining edges required.
  • Automatization
    easy to automate and monitor because it´s a mechanic mixing process.

The disadvantage is the remaining exit hole, the high forces during the welding process, require a rigid machine and a tight clamp.

Cross Section of FSSW | Al-Al

Weldable Materials

  • Aluminum in all different alloy groups
  • Aluminum of different manufacturing processes (e.g. cast and wrought alloys)
  • Aluminum / Copper
  • Aluminum / Steel
  • Aluminum / Magnesium
  • Copper / Steel
  • Thermoplastics

Applications for FSSW



HV inverter housing, Electronic motor housing and EV/PHEV battery trays
More about E-Mobility
Charging Systems / Busbars

Charging Systems / Busbars

Flat busbar and dissimilar connectors (aluminum-copper)
More about Charging Systems / Busbars
Dominik Kaineder

Your contact person: Dominik Kaineder

Are you interested in determining the feasibility of a new concept using Friction Stir Welding? Or do you require assistance in choosing the most-sufficient system for serial production for your application?
Please contact us directly - we'll gladly provide guidance and support.

+43 676 30 93 922