ROTATIONAL FRICTION AND FRICTION STIR WELDING

Friction Stir Welding (FSW) and Rotational Friction Welding (RFW) are both solid state welding processes (similar to forging) operating typically at about 80% of the base material melting temperature. After cooling down the parts undergoing the process will be joined by a quality weld.

When FSW a welding tool, consisting of a pin and shoulder, is brought into rotation and pushed into the work piece at the start of the joint. The frictional heat that is generated between the rotating and stationary surfaces softens the material that is in contact with the tool and stirs it locally. Under constant downward pressure the tool is then moved along the welding path while the material is being intensely stirred in various directions.

When RFW the components to be joined are clamped coaxially in the tooling and one of them starts spinning. Upon reaching the required rpm both parts are approached and brought into contact thus generation frictional heat. After a specific time the rotation is suddenly stopped and both parts are pressed into one another (forging stage).

Application field and advantages

  •  Possible weld configurations: for FSW butt welds and overlap welds (others are possible but subject to restrictions), for RFW  mainly butt welds (spinning part requires rotational symmetry)
    • Very large welding capacities : for FSW from rather thin (0.5 mm) up to thick (25 mm) in a single pass, RFW is a fast method for joining bars and tubes in one process cycle
    •  Weldability: typically used for non-ferrous metals specifically when metallurgical issues occur in fusion welding. For example: aluminium, copper, magnesium and most of their alloys. Welding other metals (such as steels, nickel and titatium alloys) or plastics is possible but less obvious.
    • Multi-material welds are possible and often performed between different aluminium alloys (FSW) and very different metals such as aluminium, steels, titanium (RFW)
    • Reliable and reproducible process (automation and controlled welding conditions)
    • Small deformation and no heat affected zone since the process operates below the fusion temperature. Joints typically have high mechanical resistance (compared to arc welding)
    • No protection gas (when welding non-ferrous metals) and no filler metal is needed
    • Typical FSW applications are welding of Al extrusion profiles (shipbuilding, trains), thick aluminium plates (defence, energy), various mechanical components (machine building, aeronautics)…
    • Typical RFW applications are welding of different steel grades (mining), valve heads and compressor turbines (automotive and aeronautics), various mechanical components (machine building, tools)...

      friction crm

      CRM facility


      FSW machines: ESAB 53 UTL and STL  

    • Machines for 1D up to 2.5D welding (no full 3D)
    • Max welding force: 100 kN (process control by force or position)
    • Max spindle speed: 1400 rpm and 3000 rpm
    • Welding area X - Y: 600 mm x 6000 mm
    • Max linear feed speed: 2 m/min
    • Max weldable diam (circumferentially): 2 m
    • Additionally: cooling for FSW tool, various welding tools (retractable pin, bobbin, …), accessories for welding high temp materials (steels, titanium, …)

       

      CRM facility

       FSW machines: ESAB 53 UTL and STL  

    • Machines for 1D up to 2.5D welding (no full 3D)
    • Max welding force: 100 kN (process control by force or position)
    • Max spindle speed: 1400 rpm and 3000 rpm
    • Welding area X - Y: 600 mm x 6000 mm
    • Max linear feed speed: 2 m/min
    • Max weldable diam (circumferentially): 2 m
    • Additionally: cooling for FSW tool, various welding tools (retractable pin, bobbin, …), accessories for welding high temp materials (steels, titanium, …)
       

      Rotational Friction welding machine: SMFI SF20

      friction machine

    •  Power: 20 kW
    • Machine capability: adjustable timing and forces (friction, forging…), process control by force or displacement
    • Max spindle speed: 3000 rpm
    • Max weldable diam: bars diam. 6 mm to 25 mm and tubes up to diam. 50x4 mm
    • Max forging force: 120 kN (300 bar)