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Metallurgical failures of high temperature plant are often associated with the heat affected zone (HAZ) of weldments and usually occur by a creep mechanism. Type III cracking, in the intercritical, low temperature region of the HAZ, frequently occurs during post-weld stress relief heat treatment, due to the exhaustion of creep ductility in weakened grain boundary regions. It is exacerbated by the presence of grain boundary particles which nucleate creep cavities. Microstructural solutions to the problem therefore involve refinement of the grain size in this region of the HAZ and/or removal of particles, notably MnS, from the prior austenite grain boundaries. This investigation was designed to examine the effects of TiN grain refinement and rare earth modification of sulphides on the high temperature creep properties of ½Cr½Mo¼V and 2¼Cr1Mo steels, in the normalised and welded condition, using both cross-weld and HAZ simulated samples. Two low phosphorus casts (0.007% P) were also included in the study to examine the reported effect of this element on rupture ductility. The rare earth treated 2¼CrMo steels also contained high levels of residual elements (Sb, Sn, As) to investigate the reported segregation of these elements to rare earth inclusions.

Additional information

Authors: BURKE P R, British Steel plc, London (GB)
Bibliographic Reference: EUR 13303 EN (1991) 121 pp., FS, ECU 12.50
Availability: (2)
ISBN: ISBN 92-826-2365-3
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