A method of manufacturing a recuperator segment uses metal tubes deformed into air cells in a waved configuration. The air cells are stacked one to another to form a double skinned recuperator segment providing cold air passages through the respective air cells and hot gas passages through spaces between adjacent air cells.

A method of manufacturing a recuperator segment uses metal tubes deformed into air cells in a waved configuration. The air cells are stacked one to another to form a double skinned recuperator segment providing cold air passages through the respective air cells and hot gas passages through spaces between adjacent air cells.

An object of the present invention is to provide a bending die that has a simple configuration and is capable of bending a rod-shaped body in a three-dimensional XYZ direction quickly and reliably. The bending die includes XY-plane forming dies that are to be clamped in an X direction to bend the rod-shaped body in an XY plane, and Z-direction forming dies that are to be clamped in a Z direction to bend the rod-shaped body in the Z direction, wherein when both the XY-plane forming dies and the Z-direction forming dies are clamped, a cavity that forms the rod-shaped body bent in the three-dimensional XYZ direction is defined therebetween.

A method of evaluating deformability of steel pipe with which deformability can be evaluated regardless of whether the pitch of pipe expansion is coarse or fine, and a method of manufacturing steel pipe using the method of evaluating deformability, are disclosed. A method of evaluating deformability of steel pipe according to the present invention is a method for evaluating deformability of a steel pipe manufactured through a pipe expanding step performed using a die. The method of evaluating deformability of steel pipe includes an outer shape acquiring step of measuring a shape of the steel pipe to acquire an outer shape, a power spectrum acquiring step of acquiring a power spectrum from a wavy shape of the acquired outer shape, and a determining step of integrating the acquired power spectrum for a predetermined wavelength range and determining deformability on the basis of the resulting integral.

A method of evaluating deformability of steel pipe with which deformability can be evaluated regardless of whether the pitch of pipe expansion is coarse or fine, and a method of manufacturing steel pipe using the method of evaluating deformability, are disclosed. A method of evaluating deformability of steel pipe according to the present invention is a method for evaluating deformability of a steel pipe manufactured through a pipe expanding step performed using a die. The method of evaluating deformability of steel pipe includes an outer shape acquiring step of measuring a shape of the steel pipe to acquire an outer shape, a power spectrum acquiring step of acquiring a power spectrum from a wavy shape of the acquired outer shape, and a determining step of integrating the acquired power spectrum for a predetermined wavelength range and determining deformability on the basis of the resulting integral.