PRODUCTION OF MULTILAYER TUBULAR BODY

PURPOSE:To reduce a cost due to making the thickness of a high class corrosion resistant material of the inmost layer thinner especially in case of the tubular body for corrosion resistant fluid by forming in order the inner layer inside the outer tube of rigid structure with widening the diameter of a plate material. CONSTITUTION:The 1st plate 2a is made in the condition that the side edge parts are overlapped each other with bending the plate 2a cylindrically and inserted into an outer tube of rigid structure. It is pressed by an expanding jig to widen the diameter and the outer peripheral part is closely fitted to the inner peripheral wall of the outer tube 1. No.1 inner layer 2 is fromed with the butt welding of the side edge parts on the inner peripheral wall face of the outer tube 1 further. The inner layers 3, 4 for reinforcing of the No.2 and on are then laminated in order by inserting No.2 plate which is bent cylindrically into the No.1 inner layer 2, and if necessary, by laminating the inner layer 7 for lining with said similar procedure by the plate of a corrosion resisting material of Ti, etc. a multilayer tubular body is formed. Due to the inmost layer 7 which is pressed from the inside being supported from the outside by the outer tube 1, etc. it is made possible to make the thickness of the inmost layer 7 thinner.