ボイラ過熱器 SUS 316 H 鋼管の経年劣化

概要

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Material characterization of SUS316HTB, used as boiler superheater for long time under service operating conditions, were performed by means of the Charpy impact test, the short term creep test, hardness measurement and metallographic observation. The formation of brittle sigma-phase mainly along grain bounaries is a principal cause of material degradation, in cooperation with carburization from the fire side of superheater tubes. The supporting evidences for the formation of brittle sigma-phase along grain boundaries is I.G fracture caused by the Charpy impact test (R.T ~77K) and by the creep test applied to the materials used. The Larson-Miller parameter is a useful tool for examining the effect of sigma-phase formation on various materials used in service under different conditions in operating temperature and periods. L. M. P of 22 may be a critical value for which more detailed material characterization is needed to determine the replacement time for superheater tubes. In order to verify the above approach, an appropriate estimate or direct measure of the temperature of superheate tubes is crucial.
1986-01-25