PURPOSE: To manufacture a pipe without causing buckling and rolling, by deciding the minimum roll diameter at the generating limit of edge buckling and the maximum roll diameter at the generating limit of rolling, and using a forming roll having the roll diameter satisfying a specified equation.
CONSTITUTION: An edge stretching extent ES of a sheet-shaped hoop of titanium, zirconium, or its alloy, and an edge rising angle γ are respectively obtained by changing the diameter i of a forming roll in accordnce with each pipe diameter D. The minimum roll diameter min. at the generating limit of edge buckling is decided in accordance with each pipe diameter D basing on the presence or absence of the generation of buckling at a joined part, generating in accordance with the extent ES. And also, the maximum roll diameter max. at the generating limit of rolling is decided in accordance with each pipe diameter D basing on the presence or absence of the generation of rolling of a travelling hoop, generating in accordance with an edge rising angle γ, and then a pipe having the prescribed diameter D is formed by using a forming roll having the roll diameter i which satisfies the equation 1.
MIYAMOTO YOSHIYUKI
SAWAHISA EIICHIROU
