2. • Friction welding is a
solid state joining
process that produces
coalescence by the heat
developed between two
surfaces by
mechanically induced
surface motion.
Definition of Friction Welding
3. • One of the workpieces is
attached to a rotating
motor drive, the other is
fixed in an axial motion
system.
• One workpiece is rotated
at constant speed by the
motor.
• An axial or radial force is
applied.
Continuous Drive
Workpieces
Non-rotating vise
Motor
Chuck
Spindle Hydraulic cylinder
Brake
Continuous Drive Friction
Welding
4. • The work pieces are
brought together under
pressure for a predeter-
mined time, or until a
preset upset is reached.
• Then the drive is
disengaged and a break
is applied to the rotating
work piece.
Continuous Drive
Workpieces
Non-rotating vise
Motor
Chuck
Spindle Hydraulic cylinder
Brake
Continuous Drive Friction
Welding
8. • The joint face of at
least one of the
work piece must
have circular
symmetry (usually
the rotating part).
• Typical joint
configurations
shown at right.
Rod Tube Rod to tube
Rod to plate Tube to plate Tube to disc
Continuous Drive
Friction Welding Joint Design
9. Radial Friction Welding
• Used to join collars to shafts
and tubes.
• Two tubes are clamped in
fixed position. The collar to
be joined is placed between
the tubes.
• The collar is rotated
producing frictional heat.
• Radial forces are applied to
compress the collar to
complete welding.
F
+
F
F F
F
F
F
F
F
11. Friction Stir
Welding
• Parts to be joined are
clamped firmly.
• A rotating hardened steel
tool is driven into the joint
and traversed along the joint
line between the parts.
• The rotating tool produces
friction with the parts,
generating enough heat and
deformation to weld the
parts together.
Butt welds
Overlap welds
15. • Frequently competes with flash or
upset welding when one of the work
pieces to be joined has axial symmetry.
• Used in automotive industry to
manufacture gears, engine valves, and
shock absorbers.
• Used to join jet engine compressor
parts.
Continuous Drive
Friction Welding Applications
In the general case, one part is held fixed while the other is rotated. When the two parts are brought into contact, the frictional heat generated breaks down the surface asperities under the action of the load, and surface material is plastically moved out of the interface, carrying with it any surface oxide and contamination into the outside “flash” material (gray in this figure). This flash material may or may not be subsequently machined off depending upon the final use of the part.
In continuous “direct drive” friction welding, one workpiece is attached to a rotating motor drive unit as shown above. The other workpiece is clamped in a non-rotating axial drive unit. The two workpieces are gradually brought together with one rotating and the other still. When they make contact, heat is generated at the interface due to friction. Additional axial force is applied. The axial force is raised to a final constant value and held for a predetermined time, or until a preset amount of upset takes place. The rotational driving force is disconnected, and the rotating workpiece is stopped by the application of a braking force. The axial force (forging force) is maintained or increased for a predetermined time after rotation ceases.
Continuation of previous slide
Radial friction welding is used to weld collars to shafts and tubes. For the radial friction welding of tubes, the two tubes are clamped firmly. The collar to be joined is placed between them. The collar is rotated producing frictional heating. When heated enough by friction, radial forces are imposed along the periphery of the collar. These forces compress the collar to produce the weld. An internal expanding mandrel is often used to support the tube walls.
Unlike conventional friction welding, the parts to be joined by friction stir welding are not rotated. The parts are clamped firmly in a restraining device. A rotating tool traverses along the joint line. During rotation, the tool generates frictional heating, deformation, and welding along the joint line of the workpieces. Butt joints, corner joints, T joints, and fillet-butt joints can be welded by friction stir welding.
