US Patent 7104183 One-piece steel piston

A one-piece steel piston that is made from a piston blank that includes a portion that configured and designed to be displaced to form a cooling gallery and ring belt. The piston blank can be formed by a casting or forging process. The portion that is designed and configured to be displaced is a flange that extends radially at the top of the piston blank. The flange is bent downward so that a peripheral edge of the flange contacts a top portion of the piston skirt. The peripheral edge of the flange and the top portion of the skirt can be welded together or provided with inter-engaging structures.