Method and device for improving the quality of the weld seam in friction stir welding

A method for improving the quality of a weld seam in friction stir welding comprising the following steps:

• a) effecting the friction stir welding by a device, the device comprising:
• a receiving plate with a drive head and a spindle bearing for receiving a working tool,
• wherein the spindle bearing has openings leading obliquely outward and a sliding surface,
• wherein the working tool has a friction welding tip, which includes a raised middle section, and has a transporting screw, which is machined in a spiral form in the working tool, and
• wherein the transporting screw transports away applied material that is not required through the openings,
• the sliding surface of the spindle bearing consisting of a planar sliding surface and two respective sliding surfaces, said respective sliding surfaces are for welding of curved seams, wherein said respective sliding surfaces are curved and adjoin the planar sliding surface on opposites sides thereof at a reflex angle to the planar sliding surface, and
• wherein the friction welding tip has a form of a truncated cone,
• wherein on top of the truncated cone is the raised in a middle section and a bottom of the truncated cone is in the shape of a circle,
• wherein a lateral surface of the truncated cone is formed by six trapezoidal segments, said six trapezoidal segments being distributed about a circumference of the circle,
• wherein the circle is concentric with the raised middle section, and
• wherein three of the trapezoidal segments are respectively distributed uniformly on the circumference of the circle, lie at an angle of 120 degrees with respect to one another, and account for a proportion greater than ⅙ of the circumference,
• b) inclining a longitudinal axis (L) of the spindle bearing with respect to a vertical (V) at an angle of 2.8 to 3.2 degrees for the friction stir welding.