Abstract: Provided is a friction stir spot welded joint having high joint strength even in the case where a high strength steel sheet, particularly a steel sheet with a tensile strength (TS) of 980 MPa or more, is used as a material to be welded. An annular groove is formed on an upper surface of an upper sheet out of overlapping steel sheets, and a shape, microstructure, and hardness of a welded portion are appropriately controlled simultaneously.

Abstract: A friction stir tool control method is a control method for controlling an operation of a friction stir tool by supplying a necessary drive electric current to a drive source of the tool. The control method includes obtaining a pressurizing force change ratio by comparing a set pressurizing force predefined as a pressurizing force at plunging of the tool into a workpiece with an actual pressurizing force occurring at actual plunging of the tool into the workpiece by supplying a drive electric current for generating the set pressurizing force to the drive source. The drive electric current is regulated in accordance with the pressurizing force change ratio so that the actual pressurizing force comes to the set pressurizing force, and the drive source is driven with the regulated drive electric current.

Abstract: A joining system (100) of the present invention is for joining a joining target (W) including first, second, and third members (W1), (W2), (W3), and includes a welder (101), a friction stir welding machine (102), and a controller (110) that: (A) causes the welder (101) to weld the second and third members (W2), (W3); (B), after (A), causes the joining target (W) to be placed at the friction stir welding machine (102) so that the first member (W1) is opposed to a distal end of a tool (10); and (C), after (B), controls a linear motion driver (7) and a rotation driver (8) so as to, while pressing the distal end of the tool (10) to the joining target (W), rotate the tool (10) around an axis, so that the softened second and third members (W2), (W3) intrude into the softened first member (W1), thus joining the joining target (W).

Abstract: A dissimilar metal welding method includes a preparing step and a working step. In the preparing step, a pin member is moved to a second metal material while being rotated, and a tool body is driven such that the tool body is moved in a direction away from the second metal material while being rotated. In the working step, a through-hole is formed in the second metal material by the pin member, and then a distal end of the pin member is dug into the first metal material to a predetermined depth position in the first metal material.

Abstract: A friction stir spot welder includes a pin, a shoulder, a rotary driver, an advance-retract driver, and circuitry. When a preset and predetermined first period of time has elapsed in a state where a speed of the rotating shoulder in an axial direction or a speed of the pin in the axial direction is a preset and predetermined first speed, the circuitry determines that the tip of the shoulder or the tip of the pin has reached a contact surface of a second workpiece which is in contact with a first workpiece.

Abstract: A dissimilar metal welding method includes a preparing step and a working step. In the preparing step, a pin member is moved to a second metal material while being rotated, and a tool body is driven such that the tool body is moved in a direction away from the second metal material while being rotated. In the working step, a through-hole is formed in the second metal material by the pin member, and then a distal end of the pin member is dug into the first metal material to a predetermined depth position in the first metal material.

Abstract: A friction stir spot welding apparatus includes a pin member formed in a solid cylindrical shape, a shoulder member formed in a hollow cylindrical shape, the pin member being inserted in the shoulder member, a rotary actuator that rotates the pin member and the shoulder member on an axis that is in agreement with an axial center of the pin member, and a linear actuator that linearly moves each of the pin member and the shoulder member along the axis. A tip-end part of the shoulder member is formed in a tapered shape.

Abstract: A joining system (100) of the present invention is for joining a joining target (W) including first, second, and third members (W1), (W2), (W3), and includes a welder (101), a friction stir welding machine (102), and a controller (110) that: (A) causes the welder (101) to weld the second and third members (W2), (W3); (B), after (A), causes the joining target (W) to be placed at the friction stir welding machine (102) so that the first member (W1) is opposed to a distal end of a tool (10); and (C), after (B), controls a linear motion driver (7) and a rotation driver (8) so as to, while pressing the distal end of the tool (10) to the joining target (W), rotate the tool (10) around an axis, so that the softened second and third members (W2), (W3) intrude into the softened first member (W1), thus joining the joining target (W).

Abstract: A dissimilar metal welding method includes a preparing step and a working step. In the preparing step, a pin member is moved to a second metal material while being rotated, and a tool body is driven such that the tool body is moved in a direction away from the second metal material while being rotated. In the working step, a through-hole is formed in the second metal material by the pin member, and then a distal end of the pin member is dug into the first metal material to a predetermined depth position in the first metal material.

Abstract: A friction spot joining device configured to carry out friction spot joining of a pair of plates includes an advance-retreat drive configured to advance and retreat a tool to/from the plates a rotation drive configured to rotate the tool, and a controller configured to control the advance-retreat drive and the rotation drive. The controller executes a joining control in which the tool is caused to give pressure to the plates while the tool is rotated so that the tool is pushed into the plates, and a separating control in which the tool is separated from the plates when an integrated value (P=ID×?T) calculated using a current value (ID) of the rotation drive during the joining control and a driving period of time (?T) during the joining control is determined to be reached a target value.

Abstract: During friction stir spot welding, a controller executes a temperature holding control in which the controller controls a rotation driving unit so that a rotational speed of a tool is set to a value which is equal to or lower than a predetermined rotational speed at which a temperature of the tool is regarded as being equal to a welding temperature of lapped portions, and in which the controller controls a displacement driving unit to increase and reduce a welding pressure or plunge depth of the tool so that the temperature of the tool is held in a predetermined set range.

Abstract: A friction stir joining device includes a tool, a rotary driver, a linear-movement driver, and a control device. The control device is adapted to (A) dispose so that a first member opposes to the tool, and the first member, a second member and a third member are located in this order, (B) control the linear-movement driver and the rotary driver so that a tip-end part of the tool presses a joined part of a to-be-joined object while the tool is rotated, (C) control the linear-movement driver and the rotary driver so that the third member softened extends above an upper surface of the second member, and the tip-end part of the tool reaches a first position, and (D) control the linear-movement driver and the rotary driver so that the tool is drawn out from the joined part while the tool is rotated.

Abstract: A method of performing friction stir spot welding of a plurality of steel plates, includes the steps of: friction stirring a spot welding portion of the plurality of steel plates by pressing a tool against the spot welding portion while rotating the tool, to plasticize the spot welding portion by friction heat; cooling the spot welding portion to cause martensitic transformation to occur in the spot welding portion, after the step of friction stirring the spot welding portion; and tempering the spot welding portion by the friction heat by re-pressing the tool against the spot welding portion while rotating the tool, after the step of cooling the spot welding portion.

Abstract: A spot welding apparatus which performs spot welding of a plurality of plate materials which are lapped to each other, comprises a displacement driving unit which displaces lapped portions of the plurality of plate materials and a tool relatively to each other; a rotation driving unit which rotates the tool; and a controller which controls the displacement driving unit and the rotation driving unit so that the tool is plunged into the lapped portions in a state in which the tool is rotated to perform friction stir spot welding. The controller controls the displacement driving unit so that at least one friction stir spot weld is formed in a region of the lapped portions which is between a plurality of resistance spot welds formed by resistance spot welding.

Abstract: A friction stir spot joining apparatus for spot-joining a pair of plate members by friction stirring with a tool's pin portion includes an advancing and retracting driving device configured to advance and retract the tool to and from plate members, a rotationally driving device configured to rotate the tool, and control device configured to control advancing and retracting driving device and rotationally driving device. The control device executes joining control of pushing pin portion into plate members while the tool is rotated and causing pin portion to pressurize plate members, and executes heat dissipation control of reducing at least one of a rotation speed and a tool's pressurization force more than in the joining control while tool is rotated and pin portion is kept pushed into plate members after joining control and separating tool from plate members after the pin portion's surface temperature becomes less than an oxidation onset temperature.

Abstract: A friction stir spot joining apparatus includes a tool configured to be brought into contact with or separated from a surface of a second plate member on the opposite side to a first plate member of the first and second plate members that are overlaid on each other, a driving unit configured to rotationally drive the tool around its axis, a position adjusting unit configured to adjust a relative position between the tool and the second plate member, a control unit configured to control the driving unit and the position adjusting unit, and a breakage detection unit configured to detect breakage of the tool by controlling the control unit to dispose the tool at a contact position with the second plate member or a predetermined pushed position at one joining position.

Abstract: A friction welding apparatus is provided, which includes a tool, a rotary driver, a linear driver, and a control device. The control device controls the linear driver and the rotary driver so that the tool is rotated while a tip-end part thereof is pressed against a to-be-joined part of a to-be-joined object to increase a temperature of the to-be-joined part at or above an A1 transformation point, the tip-end part of the tool reaches a given first position so that a softened second member sticks into a softened first member, and the tool is drawn out from the to-be-joined part while the tool is rotated.

Abstract: A method of performing friction stir spot welding of a plurality of steel plates, includes the steps of: friction stirring a spot welding portion of the plurality of steel plates by pressing a tool against the spot welding portion while rotating the tool, to plasticize the spot welding portion by friction heat; cooling the spot welding portion to cause martensitic transformation to occur in the spot welding portion, after the step of friction stirring the spot welding portion; and tempering the spot welding portion by the friction heat by re-pressing the tool against the spot welding portion while rotating the tool, after the step of cooling the spot welding portion.

Abstract: During friction stir spot welding, a controller executes a temperature holding control in which the controller controls a rotation driving unit so that a rotational speed of a tool is set to a value which is equal to or lower than a predetermined rotational speed at which a temperature of the tool is regarded as being equal to a welding temperature of lapped portions, and in which the controller controls a displacement driving unit to increase and reduce a welding pressure or plunge depth of the tool so that the temperature of the tool is held in a predetermined set range.

Abstract: A spot welding apparatus which performs spot welding of a plurality of plate materials which are lapped to each other, comprises a displacement driving unit which displaces lapped portions of the plurality of plate materials and a tool relatively to each other; a rotation driving unit which rotates the tool; and a controller which controls the displacement driving unit and the rotation driving unit so that the tool is plunged into the lapped portions in a state in which the tool is rotated to perform friction stir spot welding. The controller controls the displacement driving unit so that at least one friction stir spot weld is formed in a region of the lapped portions which is between a plurality of resistance spot welds formed by resistance spot welding.