Corrosion fatigue strength of ship structural steel plates and their welded joints in sour crude oil

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:27928

Watanabe, Eiichi ^[1]; Yajima, Hiroshi ^[2]; Ebara, Ryuichiro ^[3]; Matsumoto, Shigato; Nakano, Yoshifumi ^[4]; Sugie, Eiji ^[5]

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1. Mitsubishi Heavy Industry, Ltd., Nagasaki (Japan)
2. Mitsubishi Heavy Industry, Ltd., Tokyo (Japan)
3. Mitsubishi Heavy Industry, Ltd., Hiroshima (Japan). Hiroshima R and D Center
4. Iron and Steel Research Labs., Chiba (Japan)
5. Kawasaki Steel Corp. (Japan)

This presentation is mainly on the corrosion fatigue crack propagation behavior of the ship structural steels such as KA36 (TMCP) and KAS in a sour crude oil environment, based on the corrosion fatigue crack propagation test and corrosion fatigue life test results in sour crude oil containing 400 ppm H{sub 2}S and in air. The crack propagation rate of the base metals of these steels in the sour crude oil was accelerated in the stress intensity factor range, {Delta}K higher than about 16 MPa/m. The ratio of acceleration of the crack propagation rate, da/dN, in the sour crude oil with the {Delta}K of 30 MPa/m was 7 for KA36 (TMCP) and KA36 steels. The crack propagation rate of the heat affected zone and the weld metal of the KA36 (TMCP) in the sour crude oil was also accelerated for the {Delta}K higher than about 20 to 25 MPA/m. In the higher stress range of S-N curves for the notched round bar specimens of the KA36 (TMCP), the influence of sour crude oil containing 400 ppm H{sub 2}S on the fatigue life was obviously observed. The ratio of fatigue life in air to that in the sour crude oil decreased with decreasing stress to unity at the lower axial stress of about 200 MPa. It was found that brittle striations appeared predominantly in the accelerated crack propagation area of the fracture surface of the base metal and weldments in the sour crude oil. The striation spacing per cycle, S, obtained from the measured striation spacing {Delta}S versus {Delta}K curve was well in agreement with the da/dN {approximately} {Delta}K curve in the accelerated crack propagation area. It can be concluded that the environment enhancement of the crack propagation rate in sour crude oil is dependent on hydrogen evolved by the reaction between the ship structural steels and the hydrogen sulfide in sour crude oil.

• OSTI ID: 27928
• Report Number(s): CONF-940230--; ISBN 0-7918-1266-9
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
36 MATERIALS SCIENCE
CHEMICAL COMPOSITION
CORROSION FATIGUE
CRACK PROPAGATION
HYDROGEN SULFIDES
MECHANICAL PROPERTIES
MICROSTRUCTURE
NOTCHES
S-N DIAGRAM
SAMPLE PREPARATION
SCANNING ELECTRON MICROSCOPY
SOUR CRUDES
STEELS
STRIATIONS
TANKER SHIPS
WELDED JOINTS