Patent ID: 7866044

Claim:
A method of producing a metal tubular member, said metal tubular member having two or more tube forming bodies and mutually superposed sections between the tube forming bodies in at least one position, comprising: integrally joining by welding one open annular end section of one of said tube forming bodies positioned inside the superposed sections and the other open annular end section of the other of said tube forming bodies positioned outside, wherein said other annular end section reaches a holding section within a die after passing through a tapered section provided in the die on an insertion side thereof and undergoing machining for diametral contraction, and is held by the holding section; inserting said one annular end section, in a state of being so pressurized by said die as to make an outside diameter thereof smaller than an inside diameter of said other annular end section having undergone machining for diametral contraction, into said other annular end section; and releasing said other annular end section outside from the pressurizing force by being released from said die while said one annular end section inside is released from said pressurizing force, to cause said one annular end section inside to be brought by springing back thereof into tight contact with the inside face of said other annular end section outside.