Friction stir welding method, frame members used therein, and product formed thereby

An extruded frame member adapted to be welded by friction stir welding, having two plates and plural plate members connecting said two plates, said two plates respectively having ends which are each in substantially a same plane, said ends of said two plates being in substantially a same plane, said plate having plural ribs at only one face of said plate, said plate having a second face opposite to said one face, an end of said plate extending substantially in a plane between said one face and said second face, wherein

• end portions, extending from said ends in a width direction, of said two plates, have a raised portion which projects to an outer side in a thickness direction of said extruded frame member and are provided in a side of said plural ribs, said raised portion being where said friction stir welding is carried out, wherein said end portion, including said raised portion, is adapted to be friction stir welded from an upper side of said raised portion;
• said raised portion includes a first part that extends above said end portion and a second part that extends in a direction substantially in parallel with said end portion and beyond said respective end of said two plates, said second part being formed continuously with the first part, only said raised portion, of said extruded frame member, extending beyond said ends;
• thereby on both of said respective raised portions of said two plates, friction stir welding is carried out.