Abstract: An orbital vibration generator means comprising, in addition to a clamp 4, 5 for holding a pair of thermo plastic pipes coaxially and a pressurizing means 2, 3, 14 for bringing into contact under a pressure junction end faces of a pair of thermo plastic pipes 10, 11 held by these clamps, a crank shaft 8 having a shaft portion 8a and a crank portion 8b in which the axes of these shaft portion 8a and crank portion 8b are eccentric, a motor 6 for giving rotation to the crank shaft 8, a bearing 9 attached to the crank portion 8b of said crank shaft 8, and a orbital vibration clamp 13 holding pipe an end portion of a thermo plastic pipe, formed integrally with the outer ring of the bearing 9 to move integrally with said bearing.

Abstract: An orbital vibration generator means comprising, in addition to a clamp 4, 5 for holding a pair of thermo plastic pipes coaxially and a pressurizing means 2, 3, 14 for bringing into contact under a pressure junction end faces of a pair of thermo plastic pipes 10, 11 held by these clamps, a crank shaft 8 having a shaft portion 8a and a crank portion 8b in which the axes of these shaft portion 8a and crank portion 8b are eccentric, a motor 6 for giving rotation to the crank shaft 8, a bearing 9 attached to the crank portion 8b of said crank shaft 8, and a orbital vibration clamp 13 holding pipe an end portion of a thermo plastic pipe, formed integrally with the outer ring of the bearing 9 to move integrally with said bearing.

Abstract: Circular pipe of large diameter progressively formed of flat stock, the pipe having a single longitudinal seam is seam-welded by preparing welding grooves such that the inner groove is smaller in size and angle than the outer groove, sequentially carrying out submerged arc welding on the inner welding groove, and large current MIG welding to then first layer of the outer welding edge and a submerged arc welding to a second layer thereof.

Abstract: An arc welding method for manufacture of a welded steel pipe wherein the edges of a steel plate bent into a pipe shape are welded together on one side for forming a pipe and then the seam line of the thus formed pipe is welded by a second welding operation at the side opposite to the side where the first welding was performed. During such second welding, the weld is cooled forcedly from the side where the first welding was performed. Such forced cooling compensates for any physical effects accompanying the welding and imparts elevated toughness to both the weld metal and the heat affected zone.