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X-ray residual stress measurements at SCC-damaged welds of an ammonia storage vessel

Röntgfeneigenspannungsbestimmungen an durch Spannungsrißkorrosion geschädigten Schweißnähten eines Ammoniak-Druckbehälters
 
: Backfisch, W.; Pfeiffer, W.; Prümmer, R.

2nd International Conference on Research Stresses '89. Proceedings
Essex, 1989
International Conference on Residual Stresses <2, 1988, Nancy>
Englisch
Konferenzbeitrag
Fraunhofer IWM ()
Ammoniak; Druckbehälter; Eigenspannung; Röntgenbeugung; Schweißen; Spannungsriß-Korrosion

Abstract
After about two years of operation the surface crack examination of cylindrical pressure vessel (PV) for liquid ammonia revealed fine surface cracks. They were exclusively located in the weld material of the longitudinal and circumferential joints performed by the submerged arc welding process. For the construction of the PV the fine grained structural steel St E 355 as base metal and S2 Mo wire as filler metal were used. The cracks were oriented mainly transverse to the welding direction and their appearance seemed to be typical for ammonia induced stress corrosion cracking (SCC). Because of the low operating stress level and the steel-relief heat treatment of the whole PV, X-ray residual stress measurements (XRSM) were performed in order to decide whether SCC was possible or not. As a result of the XRSM and additional investigations it was shown that the measured residual stresses were repsonsible for crack growth by the SCC mechanism. Crack initiation was caused by hydrogen induced embrittlement (cold cracking) because the welding was performed at an interpass temperature that was too low.

: http://publica.fraunhofer.de/dokumente/PX-42211.html