Abstract: The invention relates to a device for welding cylinder-shaped and rotatable elements together. An axially displaceable electrode shaft (1) is provided in a rotatably seated pipe shaft (8). The pipe shaft (8) can be rotated with respect to the electrode shaft (1), and a connecting head (4) is provided on one end of the pipe shaft (8), which is equipped with gripper elements (5) for an interchangeable protective chamber (3). Gripper and positioning elements for a fastening cassette (31) provided for the parts (A, B) to be welded together, which is also interchangeable, are arranged in the protective chamber (3). The electrode shaft (1) extends through the connecting head (4) into the protective chamber (3).

Abstract: The device for necking pipes forces the pipe wall outward in such a way that a neck is formed around the hole. The device has a body to be inserted into the interior of the pipe and a die which is movable radially to the pipe, the outer diameter of the die corresponding to the inner diameter of the desired neck. The cylindrical outer surface of the body is dimensioned, at least in the vicinity of the necking location, in such a way that it corresponds to the cylindrical interior of the pipe so as to support the pipe from the inside during the necking operation. A bore hole or opening which is directed at least substantially radially is located at the body in the region of the cylindrical surface and is dimensioned in such a way that it receives the die or its lower part with a sliding guiding fit. The die can be moved in the guide through the bore hole or opening in the direction of the latter.