Method and apparatus for producing a longitudinally welded hollow profile

The present invention relates to a method and an apparatus for producing a longitudinally welded hollow profile (R) from a defined longitudinal edges (B1, B2) having sheet-metal blank (B), in which first the sheet metal blank (B) by means of at least two, in particular on a base plate (G ) mutually adjustable in a linear movement tool parts (2, 3) each having a recess (4, having 5), which determines the outer shape of at least a portion of the hollow profile (R), (to a slot profile Sr) is preformed, and in which then in the region of the slit profile (Sr) facing longitudinal edges (B1, B2) of the sheet metal blank (B) are welded together. The method and the apparatus enable in a simple manner, the inexpensive production of precisely shaped hollow profiles. This is achieved in that, in order to generate the slit profile (Sr), the sheet metal blank (B) by changing the relative position of the tool parts (2, 3) positioned freely around a between the tool parts (2, 3) in the longitudinal direction of the extending the sheet metal blank (B) mandrel (8) is placed, whose external shape defines the internal shape of the hollow profile (R), and that the slit profile (Sr) so obtained is subsequently one or more stages in each case by a further change of the relative position of the tool parts (2, 3) is finished deformed.