A study on 3-layer roll projection welding of large area

The metal sandwich plate has many good properties such as high specific stiffness, high specific strength, good impact absorption, effective thermal insulation and soundproofing. Several bonding methods such as brazing, adhesive bonding, projection welding and adhesive-assisted projection welding are tested for fabrication of the metal sandwich plate. Finally, a new bonding method, 3-layer roll projection welding, is introduced to fabricate the metal sandwich plate of large area for the plate width of 270 mm. The new method uses a pair of roll electrodes like in seam welding; however, the workpiece width is much wider than that of seam welding by more than ten times. Projection welding of large area is made at two internal interfaces of the 3-layer , consisting of a structured inner sheet of projection-like shape and a pair of skin sheets, when it passes through the gap between the roll electrodes. The weld quality is inspected by peeling test for various welding conditions, in order to find the optimal welding parameters. The welding sequence is to be synchronized for the given welding speed and pattern type of structured inner sheet to provide the consistent welding condition.