Weld root closure method for friction stir welds

A method of friction stir welding, the method comprising:

• (a) aligning a proposed weld line of a workpiece with a recess in a backing device, the recess sized to receive a tip of a pin for forming a weld;
• and
• (b) welding with a tool comprising a non-consumable rotating pin having a tip, the tip of the pin penetrating the workpiece at least up to a rear side of the material to produce a weld bead comprising commingled material of the workpiece, the bead extending into the recess.

A method of friction stir welding a workpiece to produce weld root closure, the method comprising:

• friction stir welding a workpiece, comprising a difficult to friction stir weld material, with a rotating tool, the tool comprising a rotating non-consumable pin and a shoulder proximal to the pin, the pin penetrating a workpiece being welded such that a tip of the pin extends into the workpiece to a depth sufficient to form an outward projecting weld bead comprising commingled material of the workpiece, the bead extending along a rear surface of the weld.

A method of friction stir welding a workpiece to produce weld root closure, the method comprising:

• friction stir welding a workpiece with a rotating tool, while drawing the workpiece to and past a rotating pin and shoulder of the rotating tool by supporting the workpiece on a driven roller, the roller having a circumferential groove in its outer surface sized to accommodate the tip of the rotating pin, said pin penetrating the workpiece being welded such that said tip of said pin extends into the workpiece to a depth sufficient to form an outward projecting weld bead along a rear surface of the workpiece.