Method for making a structural element having a generally tubular metal wall and structural element

2/ A method according to claim 1, characterized by the fact that prior to folding the cutout blank (14, 20), at least one zone (22) of the metal blank (14, 20) is stamped.

3/ A method according to claim 1 or claim 2, characterized by the fact that the welding is performed using a laser beam, preferably in transparency, through the additional covering and fixing tab of each segment (19) and the additional tab for fixing segments (19) together, and at least one of the folded portion of a wall of the structural element (11, 18) and a second overlap tab.

4/ A method according to any one of claims 1 to 3, characterized by the fact that the sheet of metal material has a thickness lying in the range 0.05 mm to 1 mm.

5/ A structural element having a metal wall of generally tubular shape and polygonal cross-section, the element comprising at least two segments that are not in axial alignment and being characterized by the fact that it comprises a plurality of wall portions (24, 24′, 25, 26) in angular dispositions relative to one another that are joined together by fold lines in a single metal blank (20), at least one additional overlap and fixing tab (17, 27, 27′, 28) of each segment (19) and at least one additional tab for fixing segments (19) together being superposed and fixed together by at least one line or spot of overlap welding (29, 30), to at least one of a wall portion (24, 24′, 25, 26) and a second overlap tab of the element, the structural element (11, 18) as a whole being assembled together and stiffened solely by at least one weld line or spot (29, 30) of at least one overlap tab of each segment (19) and at least one tab (17) for fixing segments (19) together in a superposed position bearing resiliently on at least one of the wall portion and the second overlap and fixing tab.

6/ A structural element according to claim 5, characterized by the fact that it constitutes all or part of one of the following elements:

• a door or a window frame for building, a door, a window, a double-glazing frame, a frame or door for an electrical housing and cabinet, a silkscreen frame for a printing machine, a structural part for the construction of a land, water, or air vehicle, a hull, a motor vehicle chassis, an air frame, an airplane fuselage, a strong squirrel-cage structure for a motor vehicle, a reinforcement and holding structure for metal construction, a complex curved section member of polygonal section, an annular piece of hollow polygonal section, an element of a heat exchanger.