Friction stir welding method including positioning of rotary tool, and structural body formed thereby

A friction stir welding method, comprising:

• abutting an end portion of a first member and an end portion of a second member, to provide an abutted portion, said end portion of said first member having a protrusion portion which protrudes in a thickness direction from a face of said second member;
• inserting a rotary tool, having a smaller diameter portion extending from a tip end of a larger diameter portion, from a side of said protrusion portion, into said abutted portion, said rotary tool being inserted to a position in which said smaller diameter portion is inserted into said abutted portion including said protrusion portion, in which a boundary portion between the larger diameter portion and the smaller diameter portion is between an extension line of said face and an apex of said protrusion portion, and in which an end portion, in a radial direction, of said larger diameter portion is at an inner side from an end portion of a width direction of said protrusion portion;
• rotating said rotary tool and moving relatively said rotary tool along said abutted portion;
• and
• burying a clearance between said end portion of said first member and said end portion of said second member with materials of said first member or materials of said second member.

A structural body, comprising:

• first and second members welded to each other at an abutted portion of the first and second members, by a friction stir welding, wherein:
• the abutted portion of the first member and the second member is welded from a side of one face, of a thickness direction, of said first and second members by friction stir welding, providing a welding portion;
• connected to said welding portion, extending from said first member and said second member, are respective protrusion portions which protrude from said one face;
• said respective protrusion portions are provided prior to said friction stir welding to said first member and said second member;
• between an apex of said respective protrusion portions and an extension line of said one face, a face of said welding portion is provided;
• and
• said face of said welding portion is concavely curved against said apex of said respective protrusion portions.

A structural body, comprising:

• first and second members welded to each other at an abutted portion of the first and second members by a friction stir welding, wherein:
• the abutted portion of the first member and the second member is welded from a side of one face, of a thickness direction, of said first and second members, by friction stir welding, providing a welding portion;
• said first member comprises a first plate, a second plate which is substantially parallel to said first plate, and a third plate connecting said first plate and said second plate;
• to said first plate said second member is welded;
• connected to said welding portion, extending from said first plate and said second member, are respective protrusion portions which protrude from said one face;
• said respective protrusion portions are provided prior to said friction stir welding to said first plate and said second member;
• between an apex of said respective protrusion portions and an extension line of a face of said first plate, a face of said welding portion is provided;
• and
• said face of said welding portion is concavely curved against said apex of said respective protrusion portions.

A structural body, comprising:

• first and second members welded to each other at an abutted portion of the first and second members, by a friction stir welding, wherein:
• the abutted portion of the first member and the second member is welded from a side of one face, of a thickness direction, of said first and second members by friction stir welding, providing a welding portion;
• said first member comprises a first plate, a second plate which is substantially in parallel to said first plate, and a third plate for connecting said first plate and said second plate;
• said second member comprises a first plate, a second plate which is substantially in parallel to said first plate, and a third plate for connecting said first plate and said second plate;
• said first plate of said first member and said first plate of said second member are welded to each other from an outer portion of said members;
• connected to said welding portion, are respective protrusion portions which protrude to said outer portion from said one face from said first plates of the first and second members;
• said respective protrusion portions are provided to said first plates of the first and second members prior to the friction stir welding;
• between an apex of said respective protrusion portions and an extension line of an outer face of said first plate, a face of said welding portion is provided;
• and
• said face of said welding portion is concavely curved against said apex of said respective protrusion portions.