Method and apparatus for producing a tube partially having a non-circular cross section and having circular end portions and use thereof

The present invention relates to a method and an apparatus for producing a tube partially having a non-circular cross section and having circular end portions and use thereof. A method for the production of a tube having, in sections, a non-circular profile by deforming, comprises: providing a tube, which has a circular initial profile; conveying the tube in a hot, malleable state through a nip, which is formed by squeezing rollers and has a first nip width, which is larger than or equal to an outer dimension of the initial profile; adjusting the squeezing rollers for setting a second nip width, which is smaller than the outer dimension of the initial profile, and deforming the initial profile in said hot, malleable state for obtaining said non-circular cross section; and adjusting the squeezing rollers (1) for setting a third nip width, which is larger than or equal to the outer dimension of the initial profile, and severing said tube in a region having a circular cross section; so that respective end portions of said tube have a circular cross section. According to the invention, the tubes can be connected reliably with connecting-members or other tubes via the end portions having the circular profile using proven tube connection technologies.