Patent attributes
Provided is a method for manufacturing a liquid-cooled jacket, to reduce the size of a recessed groove on a surface of a metal member and also to reduce roughness of an abutted surface. The method includes: a placing step of placing a jacket body and a sealing body, a first main joining step of performing friction stirring by moving a main joining rotary tool around along a first abutted portion, and a second main joining step of performing friction stirring by moving the main joining rotary tool around along a second abutted portion. The main joining rotary tool has a base-end-side pin and a tip-end-side pin. A taper angle of the base-end-side pin is grater than a taper angle of the tip-end-side pin and a stairs-like pin step portion is formed on an outer circumferential surface of the tip-end-side pin.
