Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
  • B23K20/12—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding
  • B23K20/122—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding using a non-consumable tool, e.g. friction stir welding
  • B23K20/1245—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding using a non-consumable tool, e.g. friction stir welding characterised by the apparatus
  • B23K20/125—Rotary tool drive mechanism
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K20/00—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating
  • B23K20/12—Non-electric welding by applying impact or other pressure, with or without the application of heat, e.g. cladding or plating the heat being generated by friction; Friction welding

Definitions

• the present invention relates to a new improved method of friction stir welding of members, more particularly to a spot welding method, and furthermore to apparatuses to conduct such method.
• Friction stir welding is a new friction welding process representing a disruptive welding technology.
• the principles of the process and applied apparatus disclosed by WO93/10935 are based on a relative cyclic movement between a non- consumable probe of a harder material than the workpieces to be joined and the workpieces. Urging the rotating probe into the assembled adjacent workpieces along their joining line creates a plasticized region in the workpieces due to a generated frictional heat. Thus no heat is generated as in conventional friction stir welding due to a relative motion between the workpieces to be joined.
• This new welding method having the advantage of solid state bonding, has been successfully implemented on providing plate and profile seam joints not previously feasible and gains increasing popularity for numerous joining applications.
• Another object of the present invention is to provide improved modifications of friction stir welding apparatuses ensuring a substantial keyhole filling during/after the probe's retraction from the joined members.
• Fig. 1 illustrates schematically the novel principle of the improved friction stir welding by means of controlled and variable forces (exercised in the joined-to-be members).
• Fig. 2 shows schematically in a vertical cross-sectional view a construction principle of the applicable friction stir welding apparatus.
• Fig. 3 shows schematically in a vertical cross-sectional view another variant of the friction stir welding apparatus.
• the friction stir welding as described in WO93/10935 is incorporated herein by reference to the extent consistent with the present invention.
• Fig. 1 the principle of the novel friction stir welding based on a shoulder being movable independently of the pin and exercising controlled and variable (down) forces on the pre-assembled joined-to-be members is illustrated schematically as steps 1a-1 e in the basic welding cycle.
• a motor driven rotating cylindrical pin 1 is mounted in a rotating cylindrical shoulder 2 with the pin being movable along their combined central axis (from hereon denominated z-axis) independently of the shoulder during the welding cycle.
• the movement of the pin along the z-axis is controlled by an actuator (not shown in the Figure), the actuator being e.g. a milling machine, friction stir welding machine, arm of a welding robot, a hand held machine or any other applicable means.
• the movement of the shoulder along the z-axis is force controlled during the welding cycle.
• the shoulder's z-axis rotation velocity and direction can be chosen independently from the pin or be identical.
• An extra containment shoulder 21 encompassing the shoulder 2 independent of said shoulder's z-axis rotation can be an option to aid refilling of the keyhole.
• the pin itself can be either smooth, have a modified surface, or have a reverse pitch with regard to its direction of rotation; thus further enhancing the refilling of the keyhole.
• the basic welding cycle contains the following steps as shown in Figure 1 :
• Step b Penetration
• an extra containment shoulder 21 shown schematically co-axially arranged to and enveloping the shoulder 2, is lowered down to the surfaces of members A,B.
• the function of the containment shoulder 21 is to keep the excessive upcoming material under the shoulder 2 also during the following steps c and d.
• Step d Retracting
• Step e illustrates the completion of the welding cycle showing substantially reduced volume of the hole 10 by a simple "plunge/lift” operation of the tool keeping the shoulder under down force.
• Figure 2 illustrates in a cross-sectional view the apparatus for making friction stir welds with force controlled shoulder and friction stir welded spot welds in a simple form, having the shoulder 2 and pin 1 rotating at the same rotational velocity. The apparatus can also make shoulder down force controlled butt welds.
• the apparatus comprises conventionally a frame 5 that is mountable at the end of e.g. a robot arm (not shown in the Figure), milling machine, friction stir welding machine or any other applicable means.
• a hand held variant might also be viable.
• power source e.g. a motor 4
• the friction stir weld pin either with or without reversed thread pitch is fixed, thus rotating at motor speed.
• the shoulder 2 is constructed in such a manner that it has a loose splined fit with tool holder 3 and pin 1 and therefore can slide along the z-axis over the tool holder, while the rotational velocity of the shoulder is identical to that of tool holder and pin.
• Other means for restriction of the rotational freedom e.g.
• the shoulder is mounted inside an axial truss bearing 7 which is mounted in a hollow piston 9, the piston being part of a hollow hydraulic or pneumatic actuator, thus ensuring the down force control over the shoulder.
• Other means of actuation are conceivable/applicable.
• the frame 5 contains two motors, the top motor 4 having an axle going through the hollow axle of the bottom motor 4' and driving the tool holder 3 through an extension.
• the shoulder extension in itself forms a hollow axis 8 and can slide in the hollow motor axle 10 with a loose splined fit.
• the shoulder z-axis rotational degree of freedom is now constricted, effectively making the shoulder rotate with the same velocity as the hollow axle of the bottom motor. Only loose fit between shoulder and tool holder is now present, thus ensuring additionally z-axis rotational degree of freedom between these two.
• the constraining shoulder can typically for both principles be spring loaded and attached to the cover plate 11 of the piston.
• An obvious advantage of the independently rotating pin and shoulder is to separate function of heat input from the shoulder and the induced deformation by the pin rotation, which are both a function of their rotational velocity. This means more flexibility and better control with regard to the welding process parameters. Furthermore, the automatic positioning of the shoulder on the welded members will also cope with the thickness variations in the weld members ensuring uniform seam welds of improved quality when applied on butt welded members.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Pressure Welding/Diffusion-Bonding (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1999
  • 1999-10-19 NO NO995093A patent/NO995093D0/no unknown
• 2000
  • 2000-10-18 EP EP00970327A patent/EP1286805A1/de not_active Withdrawn
  • 2000-10-18 WO PCT/NO2000/000344 patent/WO2001028732A1/en not_active Application Discontinuation
  • 2000-10-18 AU AU79726/00A patent/AU7972600A/en not_active Abandoned

Non-Patent Citations (1)

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