US Patent 7918006 Method for joining ends of sections of pipe

A method for making pipe joints on successive pipe sections introduced into an oil well as assembled into a pipeline in which the joints are substantially of the same dimensions as the pipe sections to allow for subsequent plastic expansion of the sections. In each joint, a female pipe end is tapered on the inside and an adjacent male end is tapered on the outside preferably with a complementary self locking taper which also has an interference fit. The female pipe end is heated to be expanded sufficiently to be assembled onto the male end and thereafter cooled to grip the male end in a leakproof manner. For larger pipe sizes, the tapered shapes have features which interlock in a leakproof manner when engaged after assembly of the pipe ends. The tapered shapes preferably are formed by a reversibly positioned forming tool which is alternately engaged with male and female pipe ends to ensure perfectly matching shapes.