Method of friction stir welding structural body, structural body, and extruded material

A structural body, comprising:

• two hollow-shaped materials welded together;
• each of said hollow-shaped materials includes two face plates which are connected by a plurality of ribs, and an end portion of one of said face plates is projected further than an end portion of the other of said face plates;
• the projected end portions are friction stir welded together;
• a connecting material which is substantially parallel to said projected one of said face plates overlaps an end portion of each of said other face plates of said hollow-shaped materials, with the overlap being friction stir welded;
• and
• a surface of said connecting material facing said projected face plate is provided with a convex portion, and said convex portion is positioned in the vicinity of said other face plate.

An extruded material for friction stir welding, comprising:

• two face plates connected by a plurality of ribs;
• an end portion of one of said face plates is positioned near a rib at an end portion of said one of said face plates;
• an end portion of the other face plate is projected further than an end portion of said one of said face plates;
• and
• a convex portion is provided to a surface of said other face plate, closest to said one of said face plates, along the end portion of said other face plate.