Rotary Friction Welding

Process definition:

Rotary Friction welding (RFW) is a solid-state welding process where two or     more parts are axially pressed onto each other under high relative rotational movement. The thereby induced frictional heat plasticizes the material and results into an axial shortening and extrusion of a weld flash. Once the plastification   is sufficient the rotational movement is stopped while the force is maintained or increased which forms a solid bond between the parts.

Applications:

  • axial joints between arbitrary shaft, disk, tube or bar components

  • material combinations between most metallic alloys see matrix below

  • established process in almost all industrial    sectors, in particular automotive industry

Advantages:

  • many material combinations weldable

  • comparatively small heat-affected zone (HAZ)

  • fine-grain forged structure

  • welding without filler material and shielding gas

  • low weld times necessary

  • low distortion of the weld parts

  • very high static/dynamic strength of the weld, mostly higher than the base materials

  • no joint surface preparation necessary

  • very low requirements on weld parts (e.g. cleanliness, shape accuracy, etc.)

  • very suitable process for automation and mass production

  • very good process monitoring capabilities

  • no emissions, no splatter

Simulation of Rotary Friction Welding

Joint-zone state-variables plot

With the aid of the process simulation a detailed analysis of the joint properties is possible.   In the below picture  the state variables pressure, temperature and deformation along the    joint zone of a Ø10 mm full shaft friction weld are displayed over the time of the process.  The shape of the curves depicts that  the   material points of the final joint originated from  the inner of the shaft.   It is nicely seen that the state variables are not homogeneous  along the cross section of the weld. The simulation enables the    analysis of local properties within the joint and assists process     understanding    on a much higher level than only by experimental analysis. 

Material  condition plots

Friction welding resembles  a very distinct thermo-mechanical treatment of the involved materials. With the aid of the simulation the history of temperature, plastic deformation rate and von-Mises stresses of each  material point of the weld partners can be calculated. Below a statistical  evaluation of  a typical friction weld is displayed. The color depicts the  relative occurrence of  thermo-mechanical treatment   conditions. Such plots help to understand the mechanical processing modes of friction welds and  are a vivid tool for assessment of the metallurgical joint zone  properties. 

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