Method of joining together two planar members by friction stir welding, and tab plate used in the same method

Abstract

Method of joining together two planar members, by a friction stir welding operation wherein a rotary tool having a probe is moved relative to a joint region defined between the mutually butted planar members such that the probe is rotated and inserted in the joint region. The welding operation is performed by using a tab plate having a cutout formed in its end face such that the cutout has a width not smaller than a radius of a peripheral circle to be described by the shoulder surface, and a depth not smaller than a minimum radius of the probe and not larger than the radius of the peripheral circle. The tab plate is positioned such that the end face of the tab plate is in abutting contact with end faces of the planar members corresponding to a terminal portion of the joint region at which the welding operation is to be terminated, and such that a distance between a terminal end of the terminal end portion and one of opposite ends of the cutout width which is located on one side of the joint region which corresponds to an upstream side as seen in a rotating direction of the rotary tool at its leading end is not smaller than zero and not larger than a maximum radius of the probe, while a distance between the terminal end of the joint region and the other end of the cutout width is not smaller than the radius of the peripheral circle. The welding operation is terminated after the rotary tool which has been moved to the terminal end is further moved across the cutout.