Stress corrosion cracking of low alloy steels under high pressure and high temperature conditions

Book · Tue Oct 01 04:00:00 EDT 1996

OSTI ID:367706

Friedrich, H; Frank, J; Gladen, H; Stratmann, M ^[1]

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1. Univ. of Erlangen (Germany). Inst. for Materials Science

The stress corrosion behavior of fine grained, low alloy steels has been investigated using constant strain rate tensile tests. Studied materials were a A508 Class 2 type KS05 and a A533 B Class 1. The susceptibility to stress corrosion cracking was determined as a function of the amount of dissolved oxygen and temperature using cylindrical smooth specimen (DIN 50125) in purified water (conductivity below 0.2 {micro}S/cm). The environment was controlled and conditioned using a closed loop refreshing apparatus. The strain rate was varied between 2 {center_dot} 10{sup {minus}2} and 5 {center_dot} 10{sup {minus}9} 1/s. Most of the experiments have been carried out until fracture of the specimens. In addition some experiments were stopped after various exposure times and the specimens were broken in liquid nitrogen in order to observe initial stages of crack formation and crack propagation. The fracture surface of broken specimens has been examined by means of light and scanning electron microscopy. The fraction of brittle fracture mode on the rupture surface has been quantified in relation to exposure time to estimate a crack growth velocity. The results of the experiments indicate a lowest oxygen concentration in the water necessary for the appearance of stress corrosion cracking which is estimated to be 10 ppb. Brittle cracking generated by stress corrosion during exposure to high pressure high temperature conditions only appears beyond a preliminary plastic deformation. The value of this critical plastic deformation was found to be 3% but a lower critical value cannot be excluded. Additional stress corrosion is significant only at strain rates below 10{sup {minus}4} 1/s. Values of true crack propagation rates can be determined only after correcting for the slow straining time necessary to reach the critical elongation. At this stage crack initiation always starts at sulfide inclusions in or beneath the specimen surface.

• OSTI ID: 367706
• Report Number(s): CONF-960389--
• Country of Publication: United States
• Language: English

Related Subjects

22 GENERAL STUDIES OF NUCLEAR REACTORS
36 MATERIALS SCIENCE
CHEMICAL COMPOSITION
CRACK PROPAGATION
EXPERIMENTAL DATA
FRACTURES
NUCLEAR POWER PLANTS
REACTOR MATERIALS
STEEL-ASTM-A508
STEEL-ASTM-A533-B
STRESS CORROSION