Mannesmann Aktiengesellschaft

Mannesmannr&ouml;hren-Werke Ag

Gerold Hohl

Gerd Vogt

Gerhard Knauf

In a process for producing welded steel pipes, a pipe is molded cold from a TM-rolled sheet, welded together and sized to the desired diameter, whereby the sheet includes steel with (in wt. %) 0.02 to 0.20% carbon, 0.05 to 0.50% silicon, 0.50 to 2.50% manganese, 0.003 to 0.06% aluminum, the remainder being iron with potentially other production-related impurities. After welding and sizing, the pipe is subjected to a heat treatment process at a temperature of 100-300&deg; C. and for a holding time that is suited to the thickness of the pipe wall, with subsequent cooling with air or by forced cooling. The resulting pipe is resistant to aging and has sufficiently integral deformation reserve against fracturing with the same high degree of strength, without exceeding the upper limit for the ratio of yield strength to tensile stress according to the current industry standards for conventional steels.

Process for producing welded steel pipes with a high degree of strength, ductility and deformability

A process for the producing of pipes, in particular large pipes, by the UOE process, in which the pipes are sized by cold expansion after internal and external seam welding. In order to render the strength characteristics and deformation characteristics substantially homogeneous in the circumferential direction of the pipe and in order to adjust determined characteristics in a directed manner, the pipes are conditioned by a combined application of cold expansion and cold reduction. The sequence and degree of expansion and reduction, respectively, are established depending on the required profile.

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Neuss, Germany

Gerold Hohl