| 摘要 |
The tube (1) is formed by folding longitudinally a sheet steel strip whose face forming the tube external surface is coated with a brazing material (3). The tube has first (7,8) and second (11,12) opposite main walls connected by two complementary walls (9,10). The first main wall is formed from two zones of the median region of the strip width either side a fold (4) turned towards the tube interior. The second main wall is formed from two intermediate regions and two end regions (13,14) of the strip. The fold has a transverse U section whose side by side branches (5,6) extend perpendicularly to the main walls and form a reinforcing strut. The end regions support the bottom of the U. Each end region is folded into a U relative to the adjacent intermediate region and is supported by the bottom (15,16) of its U on the fold. |
