PROPERTIES OF HIGH TOUGHNESS 9% NI HEAVY SECTION STEEL PLATE AND ITS APPLICABILITY TO 200 000 K LNG STORAGE TANKS

Synopsis : A 50 mm thick 9% Ni steel plate containing Nb and less Si has been manufactured for LNG storage tanks with a capacity of 200 000 kl. Reduction of Si content and the addition of a Nb significantly improved HAZ toughness without a fall in strength. Furthermore, the developed steel plate and its welded joints, which were made of Ni-based weld materials, exhibited excellent strength and toughness in actual tanks. Flaw assessment proved that the developed steel plate and its welded joints have sufficient resistance to brittle fracture initiation and propagation.