HAZ fracture properties of Ti-microalloyed offshore steel in as-welded and simulated condition

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

OSTI ID:27943

Rak, I F ^[1]; Kocak, M; Petrovski, B I ^[2]; Gliha, V ^[3]

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1. Univ. of Maribor (Slovenia)
2. GKSS Research Center, Geesthacht (Germany). Inst. of Materials Research
3. Technology Research Center, Maribor (Slovenia)

This paper presents a study on the heat affected zone (HAZ) fracture toughness of submerged arc welded (SAW) joints of 40 mm thick Ti treated StE 355 grade offshore steel. The CTOD values measured on 34 mm thick SENB specimens taken from multipass 1/2K joints were compared with the values obtained from 8 mm thick SENB specimens with simulated microstructures of CGHAZ at {minus}10 C (a/W=0.5). Single and double thermal cycles were used to simulate various thermal treatments which HAZ may experience during welding. The microstructural examination of these simulated specimens show the presence of the local brittle zones (LBZ) in the CGHAZ in spite of the steel being Ti-microalloyed. The CTOD fracture toughness testing of the simulated specimens can produce toughness values not affected by the mechanical heterogeneity (strength mis-match between weld and base metals) provided the microstructure of interest has been simulated correctly. Seven different thermal simulations were examined, one single cycle and six double cycles. The peak temperature of the first thermal cycle was always above 1,350 C and cooling time (800--500 C) was about 40 sec. The peak temperature of the second thermal cycle was varied between 700 and 1,025 C and cooling time was 40 sec as well which reflects the situation in the multipass HAZ of the real joint adjacent to the fusion line. The measurement of fracture toughness and metallographical examination prove that a second thermal cycle below AC{sub 1} and between AC{sub 1} and AC{sub 3} does not improve the lowest toughness values of the unaffected CGHAZ. The CTOD results of the simulated and real weld specimens show similar toughness values in terms of stable crack initiation (CTOD at {Delta}a=0.2 mm). However, the CTOD values obtained after stable crack growth ({delta}{sub u} or {delta}{sub m}) show no correlation between both sets of data.

• OSTI ID: 27943
• Report Number(s): CONF-940230-; ISBN 0-7918-1266-9; TRN: IM9516%%69
• Resource Relation: Conference: 13. international conference on offshore mechanics and Arctic engineering (OMAE-13), Houston, TX (United States), 27 Feb - 3 Mar 1994; Other Information: PBD: 1994; Related Information: Is Part Of OMAE 1994. Volume 3: Materials Engineering; Salama, M.M.; Toyoda, Masao; Lui, S.; Dos Santos, J.F.; Kocak, M.; Patterson, E.A.; Berge, S. [eds.]; PB: 438 p.
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES
MANGANESE STEELS
FRACTURE PROPERTIES
MICROSTRUCTURE
TITANIUM ALLOYS
WELDED JOINTS
OFFSHORE PLATFORMS
HEAT AFFECTED ZONE
CHEMICAL COMPOSITION
GRAIN BOUNDARIES
SIMULATION
CHARPY TEST
CRACKS
TRANSMISSION ELECTRON MICROSCOPY
MECHANICAL PROPERTIES