Stress Corrosion Cracking of Pressure Vessel Steels in High-Temperature Caustic Aluminate Solutions

摘要

Stress corrosion cracking (SCC) behavior of three kinds of low alloy pressure vessel steels in high-temperature (200 deg C to 300 deg C) caustic aluminate (AlO_2~-) solutions has been studied by slow strain rate tests (SSRT). The results indicate that these pressure vessel steels are susceptible to SCC in caustic aluminate solution and that the SCC susceptibility increases with increasing temperature between 200 deg C to 300 deg C. Sulfide content and stringered sulfide inclusions severely and anisotropically affect the caustic SCC of these low alloy steels. The inclusions in the rare-earth-treated steel are predominantly globular rare-earth sulfides or oxysulfides, resulting in improved transverse properties. The effect of inclusions on SCC behavior correlates with the projected area of inclusions per unit volume at the crack tip, A_v, on the plane perpendicular to the tensile direction. The susceptibility to SCC increases with increasing A_v.