Production of high strength TMCP steel plate for offshore structures
- Nippon Steel Corp., Kimitsu City (Japan)
- Nippon Steel Corp., Tokyo (Japan). Plate Technical Div.
Titanium-oxide bearing steel (Ti-O steel), which has improved toughness in the heat-affected zone (HAZ) by utilizing intragranular ferrite (IGF), has been developed, and successfully put into commercial production. This was also the first application of yield strength (YS) 420 N/mm{sup 2} class TMCP steel plates to offshore structures. In the Ti-O steel, IGF grows radially from Ti-oxides finely dispersed in the steel as nuclei when HAZ transforms from austenite to ferrite after welding, and thus the microstructure of the HAZ is remarkably refined. As Ti-oxide particles are chemically stable even in the region near the fusion line which was reheated to a high-temperature above 1,350 C, control of the microstructure is possible in the entire HAZ and excellent crack tip opening displacement (CTOD) properties can be obtained. By applying Ti-O steel, Nippon Steel has succeeded in the mass production (approximately 9,000 tons) of YS 420 N/mm{sup 2} class TMCP steel plate for offshore structures in the North Sea. In addition to high strength and strict CTOD properties, various other properties including low carbon equivalent, narrow YS range, etc., were required for this plate. In order to satisfy these requirements, it was necessary to take comprehensive measured in the entire production process including steel making, continuous casting and plate rolling. The Ti-O steel with low carbon equivalent satisfies the required strength and low-temperature toughness of the base material and exhibits excellent toughness in the CTOD and Charpy tests of the welded joints, and offers good field weldability. Furthermore, the YS was controlled within a narrow range of less than 100 N/mm{sup 2} by strictly controlling the range of chemical composition and the TMCP condition.
- OSTI ID:
- 33203
- Report Number(s):
- CONF-930641--; ISBN 0-7918-0785-1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
42 ENGINEERING
AUSTENITE
CASTING
CHARPY TEST
CHEMICAL COMPOSITION
EXPERIMENTAL DATA
FERRITES
FRACTURE MECHANICS
HARDNESS
HEAT AFFECTED ZONE
MANGANESE STEELS
MECHANICAL PROPERTIES
MICROSTRUCTURE
OFFSHORE PLATFORMS
PRODUCTION
ROLLING
TENSILE PROPERTIES
TITANIUM ADDITIONS
WELDED JOINTS