dispositivo e método de soldagem a ponto por fricção e mistura mecânica

A tool driving section of a friction stir spot welding device is configured to advance and retract each of a pin member (11) and a shoulder member (12). A tool driving control section is configured to control the tool driving section such that an absolute value of a tool average position Tx defined by a following equation: Ap·Pp + As·Ps = Tx, where Ap is a cross-section area of a front end surface of the pin member (11), As is a cross-section area of a front end surface of the shoulder member (12), Pp is a press-fit depth of the pin member (11) press-fitted from a front surface of an object to be welded (60), and Ps is a press-fit depth of the shoulder member (12) press-fitted from the front surface of the object to be welded (60),is small. Thus, especially in a double acting friction stir spot welding, excellent welding quality can be accurately achieved according to welding conditions, and an internal cavity defect can be prevented or suppressed.