製鉄ガス-重油混焼ボイラーにおけるオーステナイトステンレス鋼管の高温腐食
1979 年 65 巻 7 号 p. 788-797
詳細
1979 年 65 巻 7 号 p. 788-797
Changes of appearances and metallurgical structures occurred by high temperature corrosion in austenitic stainless steel tubes during long time use for superheaters and reheaters of BFG, COG and oil mixed fired boilers were investigated. Corrosion of this type is occurred by molten deposit containing Na, V, Fe, S and SO2 in combustion gas, and is accelerated after long time operation over 20000 hours.
In corroded tubes, sulfidization, carburization and Cr-depletion were always observed, and corrosion is progtessed by the cycles of (sulfidization→carburization→Cr-depletion→oxidization).
On the basis of these results, the model of corrosion mechanism is presumed that scale on the tubes is changed and desolved into molten deposit at early stage and Cr in carburized zone under sulfidized layer is rapidly consumed through molten Ni-Ni3S2-eutectic by SO2, CO2 from molten deposit at progressed stage, and discontinuous oxidization of these Cr-depleted zones follows.
