Abstract: An externally and internally enhanced welded tube formed from a strip having a thickness b. The tube includes an inner wall enhanced with a first desired pattern having a thickness of a. An outer wail is enhanced with a second desired pattern, the second desired pattern having a thickness c. The weld fusing a portion of adjacent longitudinal edges of the strip wherein a weld bead associated with said weld is recessed within said desired patterns, does not extend beyond said desired patterns, and the length of said portion of said adjacent longitudinal edges that is fused together is from about (b+0.05a+0.05c) to about (b+0.2a+0.2c).

Abstract: A metallic strip having at least one surface enhanced with a texture pattern is formed into a welded tube. A fin insert shapes the edges of the metallic strip prior to welding and minimizes the formation of a protruding weld bead. The longitudinally running edges of the metallic strip adjacent to the enhancement are angled so that the unenhanced portions of the strip edges contact during welding. By having the unenhanced portions contact, fluctuations in metal volume during welding are reduced. This reduces weld instability.

Abstract: There is provided a method for the manufacture of a welded tube having an enhanced inner wall. A fin insert shapes the edges of a metallic strip prior to welding and minimizes the formation of a weld bead inside the tube. The portion of the edge of the metallic strip adjacent the outer surface of the tube is formed to a first angle, while that portion of the edge adjacent an inner wall of the tube is formed to a second, lesser angle.