Service Experience with duplex stainless steels in the chemical industry

Abstract

Dedicated to Prof. Dr. D. Werner on the occasion of his 60th birthdayThe 22% Cr, 5% Ni and 3% Mo grade of duplex stainless steel is by far the most used duplex grade in the chemical process industry. Duplex steels have conquered a portion of about 6% of all highly alloyed materials used to combat corrosion in chemical industry. The main areas being chloride containing aqueous media with pH values not to low-duplex steels are used there for their high stress corrosion resistance. Other fields of application are hot caustic soda at relatively low temperatures where nickel or nickel base alloys can be replaced, and media where high nickel contents are unfavourable to the corrosion resistance. Some literature findings showing other possible fields of special application of "standard" 221513 and a150 of so called superduplex grades are critically evaluated. Betriebserfahrungen mit Duplexstahlen in der chemischen lndustrieDie mit 22% Cr, 5% Ni und 3% Mo legierten Duplexstahle stellen die am haufigsten in der Chemietechnik eingesetzten Duplexguten dar. Sie haben dort cinen Anteil von 6% aller hochlegierten und korrosionsbestandigen Werkstoffe erreicht.Das Haupteinsatzgebiet stellen chloridhaltige, waBrige Medien mit nicht zu geringem pH-Wert dar, in denen Duplex-Stahle eine hohe Bestandigkeit gegenuber Spannungsriljkorrosion besitzen.Andere Einsatzgebiete sind heiRe Natronlauge bei relativ niedrigen Temperaturen, wo Duplex-Stahle Nickel-und Nickelbasislegierungen ersetzen konnen, sowie Medien, in denen hohe Nickelgehalte mit ungunstigen Bestandigkeitseigenschaften verbunden sind .Literaturangaben, aus dcnen mogliche weitere und spezielle Anwendungsgebiete fur die 221513-GCte sowie die sogenannten Superduplex-Guten hervorgehen, werden kritisch beleuchtet .

Application of ANOVA method to precipitation behaviour studies

“…DSSs composed of ␦-ferrite and ␥-austenite offer a great combination of properties, so that they are suitable for many industrial applications [9,10]. During inappropriate heat treatment or prolonged exposure at elevated temperature, the precipitation of various secondary phases, like secondary austenite (␥ 2 ), chromium carbides, nitrides, -phase and other intermetallic phases [11][12][13][14] can take place, causing the time-dependent degradation of the material and particularly its pitting corrosion resistance [15][16][17].…”