To obtain a good joined part by providing the projecting parts protruded to both parts in the thickness direction of members in the end parts of the first member and the end parts of the second member at the butted positions and friction-joining each butted portion with a rotary tool inserted from the projecting part side.
The protruded projection parts 37a, 38a are provided on the surface sides of two hollow shape materials 31, 32. The heights of the projecting parts 37a are equal to the heights of the projecting parts 38a. The friction- joining is executed by inserting the projecting part of the rotary tool into the joining parts of the hollow shape materials 31, 32 by rotating and shifting along the joining parts. By this method, even if there is a gap between the projecting part 37a and the projecting part 38a before friction-joining, the volumes of the projection parts 37a, 38a are filled up in the gap by friction-joining. Further, the projecting part 37a and the projecting part 38a are plastically fluidized with the rotary tool at the time of joining, and push-fluidized downward, and since the volume of the fluidized member is filled up into the gap, the development of the void is prevented and the good joining is executed.
ISHIMARU YASUO
TAKENAKA TAKESHI
