Patent ID: 7243471

Claim:
A hollow shape member for friction stir welding, extending in a thickness direction and in a width direction, and capable of being friction stir welded to a second hollow shape member having projections or grooves extending in the width direction, comprising: two face plates, each having respective end portions extending inward from ends of the two face plates in the width direction of the hollow shape member, each of the two face plates having a thickness in the thickness direction of the hollow shape member; a first connecting plate for connecting said two face plates, one end of which is connected to a location of one of the two face plates other than at an end portion, of the respective end portions, in the width direction of the hollow shape member; a second connecting plate for connecting said respective end portions of said two face plates, disposed substantially orthogonal to said face plates; recessed portions provided respectively to each connecting portion where said two face plates are connected with said second connecting plate, each recessed portion opening outward toward both the width direction and the thickness direction of said hollow shape member; and grooves opening outwardly in the width direction, or projections protruding outwardly in the width direction, formed at said recessed portions, respectively, wherein said grooves of said hollow shape member are capable of having projections of the second hollow shape member positioned in said grooves, and said projections of said hollow shape member are capable of being positioned in grooves of the second hollow shape member, when the hollow shape member and the second hollow shape member abut each other for the friction stir welding.