WELDED PIPE AND PIPE WELDING METHOD

摘要

A welded pipe obtained by liquid-phase diffusion welding of pipes with an intermediate insert having a lower melting point than the pipes, wherein the joint has an increased outer diameter and a decreased inner diameter. A pipe welding method having the steps of abutting the ends of pipes with an intermediate insert having a lower melting point than the pipes, heating the abutted portion to a temperature above the melting point of the insert to diffuse the insert in liquid phase into the material of the pipes so as to weld the pipes, wherein an axial pressure is applied to cause plastic deformation at the joint heated to a temperature between the A1 transformation point and keeping temperature of the pipe material, so that the joint grows in thickness.