Abstract: To produce hollow profiles from sheet-metal blanks, the invention uses at least two process steps to form said blanks into a slit profile which is subsequently welded to produce the finished welded profile. For this purpose a mandrel is used which cooperates with a first tool part in the first step, and with a second tool part in the second step, such as to form a gap with the recess of each tool part into which a portion of the sheet-metal blank is guided. Shaping the sheet-metal blank in at least two steps means that a mandrel that is a self-contained component and can therefore be moved by a simple control device can be used to support the sheet-metal blank while the slit profile is being created. This considerably reduces the equipment needed to produce the hollow profile. Moreover, forming the sheet-metal blank into the slit profile in at least two steps also considerably improves the reliability with which this shaping takes place.