A quick connect refill friction stir spot welding tool includes a clamp having a first radially-projecting mounting tab configured for engaging a first mounting slot in a refill friction stir spot welding weld head. A friction sleeve is located coaxially within the clamp and has a second radially-projecting mounting tab configured for engaging a second mounting slot in the refill friction stir spot welding weld head. The second radially-projecting mounting tab is located higher along an axis of the tool than the first radially-projecting mounting tab, and radially inward thereof. A friction pin is located coaxially within the clamp and friction sleeve. The clamp and friction sleeve are attachable to and detachable from the refill friction stir spot welding weld head by rotations through less than 360 degrees.

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=I.sub.D×ΔT) calculated using a current value (I.sub.D) of the rotation drive during the joining control and a driving period of time (ΔT) during the joining control is determined to be reached a target value.

An object of the present invention is to provide a joining method by which metal members can be suitably joined to each other. The present invention is characterized by including a friction stirring process in which the first metal member, the second metal member, and the auxiliary member are joined to one another by moving the rotary tool along the inner corner portion in a state where the tip side pin which is being rotated is inserted into the inner corner portion, is in contact with the first metal member, the second metal member, and the auxiliary member, and an outer circumferential face of the base side pin is pressed against the auxiliary member.

Provided is a ceramic sintered body having high wear resistance and chipping resistance. Also provided are an insert, a cutting tool and a friction stir welding tool, each of which uses such a high-performance ceramic sintered body. The ceramic sintered body includes Al.sub.2O.sub.3 (alumina), WC (tungsten carbide) and ZrO.sub.2 (zirconia), wherein Zr (zirconium) element is present at either one or both of: (1) a grain boundary between crystal grains of the Al.sub.2O.sub.3; and (2) a grain boundary of crystal grains of the Al.sub.2O and crystal grains of the WC, wherein the ceramic sintered body contains 55.0 to 97.5 vol % of the WC, 0.1 to 18.0 vol % of the ZrO.sub.2, and the balance being the Al.sub.2O.sub.3, and wherein the ZrO.sub.2 is in a phase of tetragonal structure (T) or a mixed phase of tetragonal structure (T) and monoclinic structure (M).

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.

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.

A powder-enhanced friction stir rivet welding device includes a friction stir rivet welding spindle, a C-shaped frame and a tooling platform. The friction stir rivet welding spindle includes a rotating mechanism, a feed mechanism, a vibration-rotation mixing mechanism and a powder feeding mechanism. The friction stir rivet welding spindle is configured to realize rotation and feed movements of a rivet and feeding and mixing of a powder. The C-shaped frame is configured to fix the friction stir rivet welding spindle and the tooling platform. The tooling platform includes a force sensor, a sensor indenter, a tooling mould and a tooling platen. The tooling platform is configured to clamp a workpiece to be riveted and welded, and measure a rivet welding force of the friction stir rivet welding spindle in real time.

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.

A double-action friction stir joining system, which includes a double-action friction stir joining device, a cleaning mechanism having a dressing member, a robot, and a control device. The double-action friction stir joining device includes a first rotary driver configured to rotate a pin member and a shoulder member, and a tool driver configured to reciprocate the pin member and the shoulder member. The control device is adapted to (A) operate the tool driver so that the pin member is thrusted into the shoulder member, (B) operate the first rotary driver so that the shoulder member rotates, and (C) operate the robot so that the robot holds the double-action friction stir joining device and the dressing member contacts an inner circumferential surface of the shoulder member.

A friction stir welding method in which a first member to be welded and a second member to be welded and having a first step portion are welded by friction stir welding using a welding tool includes the steps of arranging the first member to be welded on a step supporting surface of the first step portion with a gap between the first member to be welded and a side surface of the first step portion, pushing the welding tool into the first member to be welded from a surface of the first member to be welded while rotating the welding tool and inserting the welding tool until reaching the step supporting surface of the second member to be welded and stirring the first member to be welded and the second member to be welded by rotating the welding tool to form a welding part.