1991 Volume 29 Issue 6 Pages 341-355
To cope with the demand of constructing large-scale LNG storage tanks, heavy thickness 9% Ni steel plates were developed by taking special account of chemical compositions and heat treatment. In order to assess its applicability to LNG storage tank of 140, 000kl in capacity, properties of base plates (38-45mm, mainly 40mm in thickness) and their welded joints were studied mainly from the brittle fracture initiation and arrest characteristics, using small-scale and large-scale fracture toughness testings. GTAW, SAW and SMAW methods were applied for the tests with using 70% Ni-alloy type welding materials.
Required fracture toughness for base metal and welded joint was discussed from the view point of not only the prevention of brittle fracture initiation, but also brittle crack arrest. Furthermore, corelations between Kca value and Charpy absorbed energy, Kca value and DT absorbed energy were proposed considering the effect of plate thickess.
All the test results cleared those proposed required values with a wide margin, and the safety against brittle fracture initiation and propagation was fully confirmed through large scale tests.
