MANUFACTURE OF FINNED PIPE

PURPOSE:To prevent thermal deformation and to make fin thicknesse thinner by forming V-shaped ridge on the upper part of a metallic pipe and welding central part of a fin and bending the fin into an inverted V shape to be in tight contact. CONSTITUTION:A copper pipe 2 is passed through between forming rollers to make the cross-section of the pipe to be approximately fan shaped. On the other hand a selectively absorbing film for solar heat is formed on the upper surface of an Alminum plate by a secondary electrolysis method to form a fin. Laterally central parts of the back surface of the fin are set on the ridge of the cross-section of the pipe 2, and the one electrode contact for high frequency welding is brought into contact with the lower arc section of the pipe 2 and the other electrode contact with the fin 3. And the fin 3 and pipe 2 are passed through between a pair of upper and loer welding roll to perform high frequency welding. Next, the welded fin 3 is brought into contact with the sloped area on both sides of the pipe 2 by bending the fin 3 towards the pipe side at the welded zone and further by crooking the same at the lower ends of the contact surface so as to make horizontal wings on both sides in order to produce a finned pipe.