A method for manufacturing an electric resistance welded metal pipe by butting side ends of a metal strip against each other and then welding the side ends by high frequency heating to manufacture an electric resistance welded metal pipe, each side end being provided with an inner surface side corner portion located on an inner surface side of the electric resistance welded metal pipe, the method includes a step of forming an inclined surface at the inner surface side corner portion before butting the side ends of the metal strip, and wherein the side ends are butted and welded to each other such that the inclined surface remains on an excess metal of the metal pipe after electric resistance welding and a discharged metal is not welded to the excess metal.

Welded headgear sections can be produced by using a weld tool having pins protruding from a weld region contact surface to deliver high-frequency electromagnetic energy to a weld region defined by overlapping top and bottom headgear straps. The pins fully penetrate the top strap and at least partially penetrate the bottom strap. The pins concentrate the electromagnetic energy to achieve a weld joint of acceptable weld strength and aesthetic appeal.

Welded headgear sections can be produced by using a weld tool having pins protruding from a weld region contact surface to deliver high-frequency electromagnetic energy to a weld region defined by overlapping top and bottom headgear straps. The pins fully penetrate the top strap and at least partially penetrate the bottom strap. The pins concentrate the electromagnetic energy to achieve a weld joint of acceptable weld strength and aesthetic appeal.

Welded headgear sections can be produced by using a weld tool having pins protruding from a weld region contact surface to deliver high-frequency electromagnetic energy to a weld region defined by overlapping top and bottom headgear straps. The pins fully penetrate the top strap and at least partially penetrate the bottom strap. The pins concentrate the electromagnetic energy to achieve a weld joint of acceptable weld strength and aesthetic appeal.

A method and apparatus for joining using friction and current, wherein the friction/current joining apparatus includes a friction device, a forging device, an electrical current source, and a programmable controller, as well as workpiece holders for the workpieces to be joined. The friction/current joining apparatus is controlled such that, in a contacting phase, the workpieces are initially moved along a process axis, and their mutually facing joining surfaces oriented transverse to a common process axis are brought into contact. In a grinding phase, while subjected to contact pressure by mutual relative movement, the joining surfaces, are ground together and made smooth. At the end of the grinding phase, the relative frictional movement is permanently stopped and, in a forging phase following the grinding phase, the workpieces are pressed together, plasticized, and joined while subjected to contact pressure on their contacting joining surfaces along the process axis, and subjected to conductive heating with electrical current.

Welded headgear sections can be produced by using a weld tool having pins protruding from a weld region contact surface to deliver high-frequency electromagnetic energy to a weld region defined by overlapping top and bottom headgear straps. The pins fully penetrate the top strap and at least partially penetrate the bottom strap. The pins concentrate the electromagnetic energy to achieve a weld joint of acceptable weld strength and aesthetic appeal.

Welded headgear sections can be produced by using a weld tool having pins protruding from a weld region contact surface to deliver high-frequency electromagnetic energy to a weld region defined by overlapping top and bottom headgear straps. The pins fully penetrate the top strap and at least partially penetrate the bottom strap. The pins concentrate the electromagnetic energy to achieve a weld joint of acceptable weld strength and aesthetic appeal.

Welded headgear sections can be produced by using a weld tool having pins protruding from a weld region contact surface to deliver high-frequency electromagnetic energy to a weld region defined by overlapping top and bottom headgear straps. The pins fully penetrate the top strap and at least partially penetrate the bottom strap. The pins concentrate the electromagnetic energy to achieve a weld joint of acceptable weld strength and aesthetic appeal.

Welded headgear sections can be produced by using a weld tool having pins protruding from a weld region contact surface to deliver high-frequency electromagnetic energy to a weld region defined by overlapping top and bottom headgear straps. The pins fully penetrate the top strap and at least partially penetrate the bottom strap. The pins concentrate the electromagnetic energy to achieve a weld joint of acceptable weld strength and aesthetic appeal.

Provided is a method for manufacturing an electric resistance welded metal pipe by butting side ends of a metal strip against each other and then welding the side ends by high frequency heating to manufacture an electric resistance welded metal pipe, each side end being provided with an inner surface side corner portion located on an inner surface side of the electric resistance welded metal pipe, wherein the method comprises a step of forming an inclined surface at the inner surface side corner portion before butting the side ends of the metal strip; and wherein the side ends are butted and welded to each other such that the inclined surface remains on an excess metal of the metal pipe after electric resistance welding and a discharged metal is not welded to the excess metal.