To prevent the development of recessed part in a weld zone by providing an object to be welded with a projecting part which projects toward a rotary body side, positioning the rotary body in a prescribed position and executing friction welding.
The end part of a hollow shape 50 is inserted into the end part of a hollow shape 60, and a vertical plate 54 which joins a plate 51 with a plate 52 exists in the vicinity of the end part of the hollow shape 50. End parts of thick wall parts (projecting parts) 56, 66 for joining the hollow shape 50 with the hollow shape 60 (end parts of butting parts of the hollow shapes 50, 60 (the center of a joining part)) exist on an extension line of the center in the thickness direction of the plate 54. Joining rotary bodies 70 are arranged in the vertical direction of the joining part, a small diameter parts 72 are inserted into the joining part while rotating them, and the rotary bodies are transferred in the horizontal direction along the longitudinal direction of the joining part. When the friction welding is executed, a boundary 73 between a large diameter part 71 and the small diameter part 72 of the upper side rotary body 70 is positioned in a somewhat upper side 73a than upper surfaces of the plate 51 and a plate 61, and the boundary 73 of the lower side rotary body 70 is positioned in a somewhat lower side than rear surfaces of the plate 52 and a plate 62.
ESUMI MASAKUNI
ISHIMARU YASUO
OKAMURA HISANOBU
AOTA KINYA
