The present invention provides a metal pipe bonded body formed from a plurality of metal pipes. Each metal-pipe is formed with an elongated, pre-formed portion at each end, and a central portion, each elongated, preformed portion having a constant inside diameter greater than an inside diameter of the...http://www.google.com/patents/US6405761?utm_source=gb-gplus-sharePatent US6405761 - Expandable metal-pipe bonded body and manufacturing method thereof
