Abstract: An apparatus comprising a round-like housing having two assemblies therein. In one assembly there is a group of extending members each having affixed thereto metal backing members, which are alternatively either segment-like or inverted segment-like and have mounted a pair of rollers facing each other across a weld backing strip, the extending members being movable and workable in alternative shifts. In the other assembly the extending members each have affixed thereto a roller, the extending members being movable and workable all in one movement. There are fluid cylinder mechanisms in the assemblies for moving the members in the above-mentioned manner. The aligning, the expanding and the welding of pipes are easily and stably accomplished by such apparatus performed without need of any tack welding.