CORROSION INDUCED FAILURES IN PRESTRESSED CONCRETE STRUCTURES AND PREVENTATIVE MEASURES KORROSIONSBEDINGTE SCHÄDEN IN SPANNBETONKONSTRUK- TIONEN UND HIERAUS ABGELEITETE PRÄVENTIVMASSNAHMEN DOMMAGES EN CONSEQUENCE DE CORROSION DANS DES CONSTRUCTIONS EN BETON PRECONTRAINT ET DES MESURES PREVENTIVES
During the past 40 years in Germany some serious damages in postand pre-tensioned components have been occurred because of stress corrosion cracking of prestressing steel. Especially those problems caused a great stir, where the attendant circumstances of design, execution and building materials were not unusual. But the prestressing steel was unsuited to resist the inevitable conditions on construction site and inside the construction.
Einflüsse von Werkstoff und Verarbeitung auf die Spannungsrißkorrosion von Spannstählen
In Spannbetonkonstruktionen übernehmen die hochfesten Spannstahle wesentliche Tragfunktionen. Das alkalische Milieu des umgebenden Betons bzw. Mörtels schützt die Stähle vor Korrosion und stellt somit deren Tragwirkung auf Dauer sicher.
Evolution of carbide precipitates in Hastelloy N joints during welding and post weld heat treatment
Abstract The effects of welding and post weld heat treatment (PWHT) on the morphology, composition and lattice parameter of the precipitates in the welding joints of Hastelloy N alloy have been investigated. Joint samples were prepared using a gas tungsten arc welding process with ERNiMo-2 fillers, and then solid-solution treated at 1100 °C for 20 min. After welding, eutectic M6C carbides can be observed in the heat affected zones (HAZ) and weld zones (WZ). These eutectic M6C carbides become spheroidized during the following PWHT. The concentration of Si decreases during the transformation from the primary ones to eutectic ones, and then increases during the spheroidizing process. The total concentration of Si + Cr in M6C carbides remains stable during welding and PWHT. At the same time, the heat leads to the outward diffusion of Mo from the M6C carbides, which results in a decrease of the lattice parameter.