US Patent 11679446 Friction stir welding apparatus

A friction stir welding apparatus includes a probe, a shoulder, a recess part, and an annular member. The probe is pressed to a joint part of a plurality of joined members while being rotated. The shoulder is formed so as to surround the probe at an outside in a radial direction with respect to a rotation axis of the probe. The recess part is formed on at least one of an outer circumference of the probe and an inner circumference of the shoulder. The annular member is fitted to the recess part.