Mannesmann Aktiengesellschaft

Hans-Georg Hillenbrand

Ingo Von Hagen

Rolf K Popperling

Gerhard Knauf

Gerd Junker

Johannes Arndt

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

A ferritic perlite steel is used for pipes and tubing to be highly resistant against stress corrosion cracking when exposed to H.sub.2 S, and having following alloying range, all percentages by weight: from 0.3 to 0.45 C, from 1.4 to 1.8 Mn, from 0.2 to 0.5 Si, from 0.2 to 0.5 Cr, from 0.04 to 0.1 V, up to 0.06 Nb, .ltoreq.0.003 S, the remainder being iron whereby the combined Niobium and Vandium content must obey the rule that the sum of the V content plus twice the Nb content must not be not less than 0.1%; tubing is made by hot working followed by cooling in air from the final temperature attained during hot working, so that a texture and grain size in accordance with ASTM finer than 8 obtains; the tubing has strength value of 552 N/mm.sup.2 .ltoreq.0.2% of rupture elongation limit .ltoreq.655 N/mm.sup.2 and a tensile strength exceeding 655 N/mm.sup.2.

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Düsseldorf, Germany

Hans-Georg Hillenbrand