Research progress of high strength steel for Marine engineering at home and abroad
As the key structural material of offshore engineering equipment, steel is widely used in drilling platforms, production platforms and submarine pipelines. Due to the long service time, to resist harsh wind and wave conditions for a long time, the cost of underwater repair and maintenance is extremely high, and the steel plate used is gradually developing to high strength, high toughness, easy weldability, good corrosion resistance, and large thickness and large normalization.
1. Foreign research status
At present, the four international standards followed by offshore platform steel, namely En10225 and BS7191(European standard), API(American standard), Norsok(North Sea standard), have clear provisions on the mechanical properties and design and manufacturing of offshore platform steel, but the specification of corrosion resistance is relatively lacking.
The main grades of high-strength steel used in the world's offshore platforms are 355 MPa, 420 MPa, 460 MPa, 500 MPa, 550 MPa, 620 MPa, 690 MPa, and require low temperature performance of at least -40 ℃, or even -60 ℃, and laminar-tearing resistance to Z-35%. Good corrosion resistance, the main delivery methods are TMCP, normalizing and tempering.
Japan's research on offshore platform steel is earlier, has developed a series of high-strength steel plates resistant to seawater corrosion, large line energy welding and low temperature, and the strength level has reached 980 MPa. JFE has developed nickel-bearing platform steel with a thickness of 140 mm, yield strength of 700 MPa and tensile strength of 800 MPa. At the same time, the company has formed its own enterprise standard series, the tensile strength of the steel plate for the offshore platform is 360 MPa ~ 980 MPa, and the varieties are mainly JFE-HITEN series high-strength steel plates. Using the precipitation of microalloyed elements, Nippon Steel developed HTUFF technology, The steel plates used for offshore platforms mainly include WEL-TEN series high-strength steel plates, NAW-K and COR-TEN series non-coated welded structure corrosion resistant steel plates, MARILOY series welded structure seawater corrosion resistant steel plates and NAW-TEN series Ni weathering steel plates and other varieties. In addition, Nippon Steel also produces A, D, E, F grade steel plates with yield strengths between 315 MPa and 550 MPa according to API2W, EN10225, NORSOK and BS7191 standards, with the highest strength reaching 950 MPa.
Europe, as an early region in the development of Marine resources, is in A leading position in the research and development, application, variety serialization and standardization of steel for offshore platforms, and has been able to produce A, B, D, E grade steel plates with yield strengths between 235 MPa and 690 MP. At present, the most widely used steel grades for offshore platform construction in Europe are S355, S420, S460 and S690, which have good corrosion resistance. The Ekofysk II offshore drilling platform in Norway is the first offshore platform in Europe to use the improved toughness S690Q steel plate.
2. Domestic research status
China's offshore oil development started relatively late, and its own offshore oil platform was built in the 1980s. At present, China's offshore platforms mainly use D, E and F grade steel plates with yield strength of 355 MPa ~ 460 MPa, and basically realize localization. The strength of steel used in the 3 000 m deep-water semi-submersible drilling platform "Haiyang Shiyou 981", which was designed and built independently for the first time in China, has reached 690 MPa; The fixed structure of the offshore jack-up platform in the North Sea oil area has used more than 500 MPa, or even 750 MPa high-strength steel, but the steel used in China's offshore platform is not high strength, incomplete specifications, poor corrosion resistance, and imperfect supporting technology, which still limits China's ability to independently develop Marine resources.
3. The gap between China and the international advanced level
China's offshore platforms mainly use D, E and F grade steel plates with yield strength of 355 MPa ~ 460 MPa, and basically realize localization. The yield strength of medium and thick plates produced by Angang and Nangang has reached 550 MPa, and Wuhan Iron and Steel, Baosteel and Shagang have the capacity to produce steel with yield strength of 690 MPa for offshore platforms. Product quality and performance stability, to meet the technical needs of larger specifications of products, corrosion cracking resistance, supporting welding and other aspects have problems. Most of the steel plates with high strength, thick specifications and Marine corrosion cracking resistance used in the key parts of the construction of ocean engineering still need to be imported, especially the high-toughness, corrosion-resistant and weldable ocean platform steel with good comprehensive mechanical properties and a thickness of more than 120mm and a yield strength of more than 690 MPa are basically dependent on imports.
