FRICTIONAL AGITATION JOINED MEMBER HIGH IN FATIGUE STRENGTH, ROTATIONAL TOOL FOR FRICTIONAL AGITATION JOINING FOR ITS MANUFACTURE, AND FRICTIONAL AGITATION JOINING METHOD

摘要

PROBLEM TO BE SOLVED: To provide a frictional agitation joined member in which no non-joined portion is generated down to a reverse surface of the joined member, and the sufficient joining strength (fatigue strength) is obtained. SOLUTION: A joined member is obtained by the frictional agitation joining of an agitation pin of a rotary pin without protruding the agitation pin from a reverse side of a joined member, and the joining line observed through the actual microscopic observation and the microscopic photo at the magnification of 100 or 400 of the microstructure in the longitudinal section orthogonal to the advancing direction of the rotational tool of the joining member, and rising from the reverse side of the joining member toward an upper surface satisfies the conditions (A) that there is no pressed part Pncw to check a gap Gncw to be started from a reverse side Sb of the joining member at the magnification of 100, and (B) that the vertical height of the non-joined part from the reverse side Hnw <=25μm in the non-joined part Pnw in which the angle formed by the reverse surface Sb and the butt line before joining the longitudinal section is 0-29 deg. at a part where the joining line ODEF started from the reverse side Sb of the joining member can be visually recognized at the magnification of 100 or 400.