METHOD FOR MANUFACTURING OF RECTANGULAR FRAME

Disclosed is a method for manufacturing a square frame using friction stir welding whereby sides of the frame in predetermined lengths are prepared, are welded in the shape of ′��prime;, and are usded. According to the present invention, the method includes comprises: a preparation step of preparing four sides of the frame which are made of a material that can be processed by friction stir welding; an arrangement step of arranging the sides of the frame in the shape of ′��prime;; a first welding step of performing friction stir welding on an upper side of a boundary where the sides of the frame meet; and a second welding process of performing friction stir welding on a lower side of a boundary where the sides of the frame meet. It is preferred that the first welding step and the second welding step are performed to be overlapped by each other inside the frame. On both sides of the boundary, an auxiliary plate made of the same material with that of the frame is arranged to closely contact the boundary. Therefore, a tool for friction stir welding may start operation from an outer part of the auxiliary plate and finish the operation at an inner part of the auxiliary plate.