ボイラ高温再熱蒸気管長手溶接部のクリープ破壊メカニズムの実験的検討

概要

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The creep-burst mechanism is based on a creep-burst test and the crack growth analysis of seam-welded high temperature reheat steam piping elbows. The creep-burst test was performed under conditions with the inside steam pressure at 3.04 MPa and a test temperature 70℃ above that of the serviced plant. As a result, the center of the elbow's inner side bursted after 2948 hours. Observing the bursted cross section, the greatest areal creep voids density was 12 mm in depth from the outer surface. The thickness of the oxide scale from 12 mm in depth to the outer surface was greater than the other. After Burst, a specimen near the crack was used to perform a crack growth test. This test indicated that after cracks generate inner side of a pipe, they run through the outer surface, causing the pipe to burst. Based on these findings, the creep-burst mechanism in serviced pipes can be estimated as follows. Life Fraction:Creep-burst mechanism on high energy piping. 80%:Many voids generated on the outer surface. 86%〜88%:It is presumed that cracks generate the inner side of the pipe. 92%:Microcracks generate at about a single grain boundary on the outer surface or creep void joints on the outer surface. 96%〜99%:It is presumed that microcracks run through the outer surface from the inner side of the pipe. 100%:The specimen bursts.
2000-05-25