Mannesmann Aktiengesellschaft

Mannesmannr&ouml;hren-Werke Ag

Gerhard Knauf

Gerd Junker

Ingo Von Hagen

Gerold Hohl

Hans-Georg Hillenbrand

Ronald Claus

Johannes Arndt

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 steel pipe, includes an outer corrosive-preventive protective sheath, which has a surface layer of plastic material, and a crack stopper zone extending over a section of the pipe. The crack stopper zone includes a bandage which is wrapped around the pipe section and made of high-strength fiber material imbedded in a compacted matrix of thermoplastic and thermosetting plastic. The bandage is comprised of a plurality of wound layers joined to one another via the matrix by welding or gluing.

Pipe with crack stopper feature, and process of protecting a pipe against propagation of cracks

Process and device for checking a hollow body section

Growing community of inventors

Duisburg, Germany

Gerhard Knauf