Patent ID: 8640337

Claim:
A pipe expansion method for securing a heat-transfer pipe inserted in a pipe hole in a pipe plate by expanding the pipe, comprising: a first step of roller expanding the heat-transfer pipe a predetermined distance range from a primary-side end face towards a secondary-side end face of the pipe plate; a second step of hydraulically expanding the heat-transfer pipe a predetermined distance range from the secondary-side end face towards the primary-side end face of the pipe plate with a prescribed hydraulic pressure; a third step of roller expanding a region in the heat-transfer pipe not yet expanded in the first step and the second step; and a fourth step of further hydraulically expanding the heat-transfer pipe a predetermined distance range from the secondary-side end face, or close to the secondary-side end face, towards the primary-side end face with a hydraulic pressure higher than the prescribed hydraulic pressure, the steps being performed in sequence.