To solve such a problem that the accuracy of the inside diameter is lowered by the deterioration of butt accuracy caused by the variation in thickness of a metal sheet and yield strength of its material when manufacturing a cylindrical body by welding the butt part after bending the metal sheet into an open-pipe shape.
In the method of manufacturing a cylindrical body, an expanding means 6 is inserted into the side of the inside diameter and a contracting means 7 is arranged on the side of the outside diameter to a material 3 to be worked which is roll-formed into the open-pipe shape. After forming the material to be worked into the cylindrical shape by cooperation of these expanding means and contracting means, the butt part is joined by a welding means 8.
KOKUBU SHINOBU
IWASAKI TOSHIAKI
Masuo Oiwa
Toshihide Kodama
Keigo Murakami