Mannesmann Aktiengesellschaft

Rolf K Popperling

Ingo Von Hagen

Hubertus Schlerkmann

Norbert Niehaus

Hans-Georg Hillenbrand

Ulrike Zeislmair

Gerd Heinz

Horst Bester

Weldable high-strength structural steel with 13% chromium

A method of improving the resistance to H-induced stress-corrosion cracking of articles of low- to medium-alloy structural steels which come into contact with aqueous H.sub.2 S-containing fluids and which are manufactured by one of (i) hot rolling, with or without subsequent heat treatment, (ii) by TM-rolling, with or without accelerated cooling, and (iii) by cold rolling with subsequent heat treatment and which are then cold strained from 0% to less than 2%. In order to economically increase the resistance of articles of structural steel to H-induced stress-corrosion cracking, the articles are subjected to a final annealing for a period of at least two seconds at a temperature which is at least 540.degree. C. and the upper limit of which is as follows: In the case of hot rolled or TM-rolled or normalized articles, 30K below A.sub.C1 ; in the case of hardened and tempered articles, 30K below the tempering temperature last employed.

Method of improving the resistance of articles of steel to H-induced

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.

Steel that is exposed to hydrogen sulfide

Steel is to be austenitic-ferritic at a 1:1 ratio of austenite to ferrite and contains particular alloy elements. The principal feature is, limiting the sulphure content to below 0.005% in order to obtain a particularly high toughness transversely to the main direction of working.

High-alloyed steel being resistive to corrosion by natural gas

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Mulheim, Germany

Rolf K Popperling