Manufacturing method of a structural body

A method of manufacturing a structural body, comprising the steps of:

• starting friction stir welding by inserting respective rotary tools into respective welding joints of members to be welded;
• at a first position, stopping the friction stir welding performed by one of said rotary tools by withdrawing said one of said rotary tools from its welding joint, while continuing movement along said welding joint by said one of said rotary tools accompanying the movement of others of said rotary tools;
• at a second position, starting a withdrawal of said others of said rotary tools while continuing the friction stir welding of said others of said rotary tools;
• at a third position, stopping said movement of said respective rotary tools along their welding joints and stopping the friction stir welding by completely withdrawing said others of said rotary tools from their welding joints;
• inserting said respective rotary tools to a predetermined depth in their respective welding joints, including inserting said others of said rotary tools more deeply than the insertion depth to which said others of said rotary tools had been inserted prior to the withdrawal of said others of said rotary tools at said third position;
• and
• starting the friction stir welding by starting movement of said respective rotary tools along their respective welding joints.

A method of manufacturing a structural body, comprising the steps of:

• starting friction stir welding by inserting respective rotary tools into respective welding joints of members to be welded;
• at a first position, stopping the friction stir welding performed by one of said rotary tools by withdrawing said one of said rotary tools from its welding joint, while continuing movement along said welding joint by said one of said rotary tools accompanying the movement of others of said rotary tools;
• at a second position, stopping movement of said respective rotary tools along their welding joints and stopping the friction stir welding by withdrawing said others of said rotary tools from their welding joints;
• inserting said respective rotary tools to a predetermined depth in their respective welding joints, including inserting said others of said rotary tools more deeply than the insertion depth to which said others of said rotary tools had been inserted prior to the withdrawal of said others of said rotary tools at said second position;
• and
• starting the friction stir welding by starting movement of said respective rotary tools along their respective welding joints, and then withdrawing said others of said rotary tools to said insertion depth to which said rotary tool had been inserted prior to the stopping of the movement thereof at said second position.