Abstract: The disclosure provides a friction stir welding tool which can inhibit chipping even if an adhesion matter having high hardness adheres to a tip thereof during friction stir welding of an iron-base alloy and an aluminum alloy. In the tool for friction stir welding made of high-speed tool steel that includes a minor diameter portion and a major diameter portion formed adjacently to the minor diameter portion, hardness of the tool decreases from the minor diameter portion toward the major diameter portion. The hardness of the minor diameter portion may be 65 HRC or more by Rockwell hardness C-scale, and the hardness of the major diameter portion may be 60 HRC or less by Rockwell hardness C-scale.

Abstract: A friction stir welding tool includes a probe having a front end surface and an outer circumferential surface. Outer circumferential recesses are formed in the probe. The outer circumferential recesses extend along the rotational axis of the probe up to the front end surface. The friction stir welding tool rotates the probe about the rotation axis, and embeds the probe inside a workpiece during rotation of the probe to weld the workpiece. A front end recess is formed in the front end surface. The front end recess is positioned at the central part of the front end surface, and connected to the outer circumferential recesses.

Abstract: A friction stir welding tool includes a probe having a front end surface and an outer circumferential surface. The probe has, formed therein, outer circumferential recesses extending to the front end surface along a rotation axis. The friction stir welding tool rotates the probe about the rotation axis and embeds the probe inside a workpiece during rotation of the probe to thereby weld the workpiece. The width of the outer circumferential recesses is increased toward a front end of the probe.

Abstract: A friction stir welding tool includes a probe having a front end surface and an outer circumferential surface. The outer circumferential surface has, formed therein, outer circumferential recesses extending to the front end surface. The friction stir welding tool is configured to rotate the probe about a rotation axis, and embed the probe inside a workpiece during rotation of the probe to thereby weld the workpiece. A front end recess is formed in the front end surface, and the front end recess extends to the outer circumferential surface in a manner that the front end recess does not communicate with the outer circumferential recesses.

Abstract: The disclosure provides a friction stir welding tool which can inhibit chipping even if an adhesion matter having high hardness adheres to a tip thereof during friction stir welding of an iron-base alloy and an aluminum alloy. In the tool for friction stir welding made of high-speed tool steel that includes a minor diameter portion and a major diameter portion formed adjacently to the minor diameter portion, hardness of the tool decreases from the minor diameter portion toward the major diameter portion. The hardness of the minor diameter portion may be 65 HRC or more by Rockwell hardness C-scale, and the hardness of the major diameter portion may be 60 HRC or less by Rockwell hardness C-scale.

Abstract: A friction stir welding tool welds a workpiece by rotating a probe about a rotation axis, and embedding the probe inside the workpiece during rotation of the probe from a front end of the probe to weld the workpiece. A first step and a second step are formed in an outer circumferential surface of the probe in a manner that the probe is narrowed stepwise toward the front end of the probe. A first side surface, a second side surface, and a third side surface are formed in the outer circumferential surface of the probe.

Abstract: A friction stir welding tool includes a probe having a front end surface and an outer circumferential surface. The probe has, formed therein, outer circumferential recesses extending to the front end surface along a rotation axis. The friction stir welding tool rotates the probe about the rotation axis and embeds the probe inside a workpiece during rotation of the probe to thereby weld the workpiece. The width of the outer circumferential recesses is increased toward a front end of the probe.

Abstract: A friction stir welding tool includes a shoulder having a flat front end surface perpendicular to a rotation axis, and a probe protruding from the front end surface of the shoulder. The friction stir welding tool is configured to rotate the probe about the rotation axis, and embed the probe inside a workpiece during rotation of the probe to weld the workpiece. Protrusions and a recess are formed in the front end surface of the shoulder. The protrusions are positioned remotely from the probe, and configured to guide first softened material of the workpiece softened at the time of performing friction stir welding to the probe. The recess is positioned between the protrusions and the probe.

Abstract: A friction stir welding tool includes a probe having a front end surface and an outer circumferential surface. The outer circumferential surface has, formed therein, outer circumferential recesses extending to the front end surface. The friction stir welding tool is configured to rotate the probe about a rotation axis, and embed the probe inside a workpiece during rotation of the probe to thereby weld the workpiece. A front end recess is formed in the front end surface, and the front end recess extends to the outer circumferential surface in a manner that the front end recess does not communicate with the outer circumferential recesses.

Abstract: A friction stir welding tool includes a probe having a front end surface and an outer circumferential surface. Outer circumferential recesses are formed in the probe. The outer circumferential recesses extend along the rotational axis of the probe up to the front end surface. The friction stir welding tool rotates the probe about the rotation axis, and embeds the probe inside a workpiece during rotation of the probe to weld the workpiece. A front end recess is formed in the front end surface. The front end recess is positioned at the central part of the front end surface, and connected to the outer circumferential recesses.

Abstract: The friction stir welding apparatus includes a pin (20) on which a soft nitrided layer (50) is formed. The soft nitrided layer (50) is formed of an iron lithium oxide layer (51) and a nitrided diffusion layer (52). The atom of the iron lithium oxide layer (51) penetrates into a space between atoms at the surface of the pin (20) to form the nitrided diffusion layer (52).

Abstract: The friction stir welding apparatus includes a pin (20) on which a soft nitrided layer (50) is formed. The soft nitrided layer (50) is formed of an iron lithium oxide layer (51) and a nitrided diffusion layer (52). The atom of the iron lithium oxide layer (51) penetrates into a space between atoms at the surface of the pin (20) to form the nitrided diffusion layer (52).

Abstract: Disclosed is a friction-stir joining method for joining a first member, having a base metal covered with a substance different from the base metal, with a second member with the second member placed on the first member by moving a joining tool along a joining line having thereon a joining start point and a joining finish point. The method includes steps of: inserting the joining tool into the second member at the joining start point; moving the joining tool a predetermined distance along the joining line in a direction opposite the joining finish point; causing the joining tool to turn back at a turning-back point spaced the predetermined distance from the joining start point; moving the joining tool along the joining line to the joining finish point past the joining start point; and pulling the joining tool out from the second member at the joining finish point.

Abstract: Disclosed is a friction-stir joining method for joining a first member, having a base metal covered with a substance different from the base metal, with a second member with the second member placed on the first member by moving a joining tool along a joining line having thereon a joining start point and a joining finish point. The method includes steps of inserting the joining tool into the second member at the joining start point; moving the joining tool a predetermined distance along the joining line in a direction opposite the joining finish point; causing the joining tool to turn back at a turning-back point spaced the predetermined distance from the joining start point; moving the joining tool along the joining line to the joining finish point past the joining start point; and pulling the joining tool out from the second member at the joining finish point.