| ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ KAWASAKI STEEL TECHNICAL REPORT No.40 ( May 1999 ) Steinless Steel and Steel Platel ‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘‘ |
| 420 MPa Yield Strength Steel Plate with Superior
Fracture Toughness for Arctic Offshore Structures Mitsuo Hisata, Takanori Miyake, Fumimaru Kawabata |
| Synopsis: The 75 mm thickness YP 420 MPa class steel plates have been developed for the arctic offshore structures with such required high toughness and crack arrestability as the 50% fracture appearance transition temperature (FATT) lower than -100 and the temperature of nill ductile transition (NRL TNDT) lower than-85, respectively. They were designed of the low C-low Si-Cu-Nb and 1.1 mass% Ni addition type and manufactured by MACS (multipurpose accelerated cooling system). The excellent fracture toughness of the base metal and the welded joints were verified by the fundamental testing as well as the HAZ toughness evaluation for the 5.0 kJ/mm K-bevel submerged arc welded joints with straight fusion line. The featured values are the following: As for the base metal, the 50% FATT was -95 and the NRL TNDTs were -120 and -90 at the surface and mid-thickness positions, respectively. As for the welded joints, the minimum CTOD values for the essential portions in the weldments measured at -60 were 0.38 mm, 1.20 mm, 0.52 mm for the coarse grained (CG) HAZ, the sub-critical (SC) HAZ, and the weld metal, respectively. All the values at -40 for those portions exceeded 1.60 mm. |
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