Patent ID: 7413107

Claim:
A friction stir welding method, comprising the steps of: preparing a first extruded frame member having a first face plate, a second face plate arranged in parallel with said first face plate, plural ribs for connecting said first face plate and said second face plate, and a vertical plate arranged at an end portion of said first face plate and an end portion of said second face plate and connected between said first face plate and said second face plate; preparing a second extruded frame member having a first face plate, a second face plate arranged in parallel with said first face plate, plural ribs for connecting said first face plate and said second face plate, and a vertical plate arranged at an end portion of said first face plate and an end portion of said second face plate and connected between said first face plate and said second face plate; arranging said first face plate of said first extruded frame member and said first face plate of said second extruded frame member substantially aligned; arranging said second face plate of said first extruded frame member and said second face plate of said second extruded frame member substantially aligned; arranging adjacently said vertical plate of said first extruded frame member and said vertical plate of said second extruded frame member; carrying out a first friction stir welding at an abutted portion between said end portion of said first face plate of said first extruded frame member and said end portion of said first face plate of said second extruded frame member using a first friction stir welding use rotary tool; carrying out said first friction stir welding at a connected portion between said first face plate and said vertical plate of said first extruded frame member and at a connected portion between said first face plate and said vertical plate of said second extruded frame member using said first friction stir welding use rotary tool; and forming a welding depth of said first friction stir welding to substantially have a plate thickness of said first face plate of said first extruded frame member and also to substantially have a plate thickness of said first face plate of said second extruded frame member.