Patent ID: 6978923

Claim:
A friction stir welding method comprising the steps of: preparing (a) a first member having a first part and a raised portion, protruding beyond said first part from one side in a direction of thickness of the first member, said raised portion being at an end part of said first member, and (b) a second member to be welded to said first member, said first part of said first member having a surface and said second member having a surface, said raised portion having a length extending from an end of said first member, at said end part, to an exposed surface of said first part of said first member; abutting said first member, where said raised portion of said first member is located, against said second member to be welded to each other, to provide an abutting portion; and friction stir welding said first member and said second member to be welded from a side of said raised portion of said first member, said friction stir welding being performed by moving a rotary tool along said abutting portion of said first member and said second member, said rotary tool being at said side of said raised portion of said first member, said rotary tool having a first portion of a first diameter, and having a second portion of a second diameter smaller than said first diameter and a second radius, said second radius, of said second portion, being smaller than said length of said raised portion, wherein during said friction stir welding said second portion of said rotary tool is positioned in said raised portion of said first member and during said friction stir welding said second portion of said rotary tool is positioned in said first part of said first member and in said second member, and wherein during said friction stir welding material of said raised portion of said first member fills any gaps, between said first member and said second member, which exist when said first member abuts said second member.