Abstract: A joined assembly includes: a first member; a second member which has a facing part facing the first member in a thickness direction thereof; and joints lying along the facing part to join the first member and the second member to each other. The joints include: a pair of end joints respectively located at the opposite end portions of the facing part; and an intermediate joint located between the end joints and having a lower joining strength than the end joints. The end joint includes a fastening member mechanically joining the first member and the second member. The intermediate joint includes a friction-stirred part joining the first member and the second member by friction stir.

Abstract: A double-acting tool for friction stir spot welding is used to weld a first member and a second member each formed of a thermoplastic resin molding by friction stir spot welding. An overlapping part of the first member and the second member is formed, and the tool is disposed against the overlapping part while rotating a pin and a shoulder about a rotation axis. The shoulder is plunged into the overlapping part to start friction stir. The plunging is continued until the shoulder penetrates the first member, and penetrates the second member or reaches a depth corresponding to a first thickness t1 or lager. Subsequently, the overlapping part is backfilled with a resin material overflowed due to the plunging.

Abstract: A first member formed of a thermoplastic resin molding mixed with a fiber material and a second member formed of a molding containing at least a thermoplastic resin are welded by friction stir spot welding using a double-acting tool for friction stir spot welding. An overlapping part between the first member and the second member is formed, and the tool is disposed against the overlapping part while the pin and the shoulder are rotated about the rotation axis. The pin is plunged into the overlapping part, and friction stir is performed to cause extension fibers to remain around a plunging region of the pin while the shoulder is retracted to release an overflow material. The shoulder is brought closer to the overlapping part to wrap the extension fibers into the overflow material when the overflow material is backfilled while the pin is retracted from the overlapping part.

Abstract: A friction stir spot welding method includes a welding step of performing friction stir spot welding of a workpiece by using a pin member and a shoulder member while the workpiece is supported and pressed by the end face of a clamp member and a pressing step of causing a friction stir spot welding device to press an obverse surface and a reverse surface of at least one of a friction-stirred region of the workpiece and an adjacent region adjacent to the friction-stirred region of the workpiece from a rotary tool side and an opposite side after the welding step while the pin member and the shoulder member are accommodated in an accommodation space of the clamp member.

Abstract: A friction stir spot welding apparatus includes: a pin that is columnar; a shoulder that is cylindrical, the pin being within the shoulder; a rotary driver that rotates the pin and the shoulder about an axis that coincides with a center axis of the pin; and an advance-retreat driver that advances and retreats the pin and the shoulder along the axis. A first groove is formed at a tip end portion of an outer peripheral surface of the shoulder so as to extend in a direction along the center axis of the pin.

Abstract: A friction stir spot welding method performs friction stir spot welding of a pair of workpieces having a coating film formed on at least one welding surface by using a refill friction stir spot welding device including rotary tools. The method includes removing the coating film by plunging a distal end of the shoulder member into one workpiece up to a position closer to the surface than the welding surface, while rotating the shoulder member as a rotary tool around the axis, and rotating the shoulder member in a state in which the surface of one of the pair of workpieces, with the welding surfaces being overlaid on each other, is pressed by the end face of the clamp member and performing friction stir spot welding of the pair of workpieces after the coating film removal by using the pin member and the shoulder member as rotary tools.

Abstract: A friction stir spot welding method according to one aspect of the present invention includes: performing a plunging process of moving a shoulder (28) toward a second workpiece (102) from a first workpiece (101) side while rotating a rotary tool to plunge the shoulder into the first and second workpieces; and performing a backfilling process of pushing stirred materials that have flowed into an inside of the shoulder in the plunging process out of the shoulder and backfilling a plunging hole with the stirred materials, the plunging hole being formed by the plunging of the shoulder. In the plunging process, the shoulder is plunged to a position that is shifted from a boundary between the first workpiece and the second workpiece to the second workpiece side by 1 mm or more, such that a component of a protective layer (104) is concentrated in a central portion of a stirred portion (105) when the backfilling process is completed.

Abstract: A friction stir spot welding method performs friction stir spot welding of a pair of workpieces having a coating film formed on at least one welding surface by using a refill friction stir spot welding device including rotary tools. The method includes removing the coating film by plunging a distal end of the shoulder member into one workpiece up to a position closer to the surface than the welding surface, while rotating the shoulder member as a rotary tool around the axis, and rotating the shoulder member in a state in which the surface of one of the pair of workpieces, with the welding surfaces being overlaid on each other, is pressed by the end face of the clamp member and performing friction stir spot welding of the pair of workpieces after the coating film removal by using the pin member and the shoulder member as rotary tools.

Abstract: A friction stir spot welding method includes a welding step of performing friction stir spot welding of a workpiece by using a pin member and a shoulder member while the workpiece is supported and pressed by the end face of a clamp member and a pressing step of causing a friction stir spot welding device to press an obverse surface and a reverse surface of at least one of a friction-stirred region of the workpiece and an adjacent region adjacent to the friction-stirred region of the workpiece from a rotary tool side and an opposite side after the welding step while the pin member and the shoulder member are accommodated in an accommodation space of the clamp member.

Abstract: A friction stir spot welding method according to one aspect of the present invention includes: performing a plunging process of moving a shoulder (28) toward a second workpiece (102) from a first workpiece (101) side while rotating a rotary tool to plunge the shoulder into the first and second workpieces; and performing a backfilling process of pushing stirred materials that have flowed into an inside of the shoulder in the plunging process out of the shoulder and backfilling a plunging hole with the stirred materials, the plunging hole being formed by the plunging of the shoulder. In the plunging process, the shoulder is plunged to a position that is shifted from a boundary between the first workpiece and the second workpiece to the second workpiece side by 1 mm or more, such that a component of a protective layer (104) is concentrated in a central portion of a stirred portion (105) when the backfilling process is completed.