Development And Composition Optimization Of X70 Submarine Pipeline Steel

Recent years,in order to meet the increasing requirement for resources,the recovery intensity of marine resources is enhanced,wherein,the enhancement of the recovery intensity of oil and natural gas resources directly gives rise to the requirement for submarine pipelines of each country.The present thesis,taking X65 submarine pipeline steel for the project of Lichee Bay in South China Sea of Ansteel Corporation as technical theory basis,makes an in-depth feasibility research on the specifications of X70 submarine pipeline steel,and makes several trail-production of steel plates,for the sake of trying to overcome the technical difficulty of X70 submarine pipeline steel and putting forward a rationalization production scenario.The main work is shown below.(1)The composition of X70 submarine pipeline with low carbon,low manganese and high nickel,chromium,copper and molybdenum alloy is determined through the experiment on the basis of X65 submarine pipeline steel.(2)The author studies the phase transformation of deformed austenite using Gleeble-3800 thermal simulator.The CCT curve is drawn in combination with swell increment curve,microstructure and micro-hardness.(3)The CCT curve shows that the hardness of steel plate increases with the increase of cooling rate in the composition of X70 submarine pipeline with high Ni,Cr,Cu and Mo content.When the cooling rate reaches 50 ?/s,the hardness of steel plate begins to decrease.(4)The experimental result shows that the corrosion resistance of the X70 submarine pipeline steel can be improved by increasing the contents of Ni,Cr and Mo while decreasing the content of Cu.(5)A research on controlling of drop-weight tear performance of deep-sea and large-thickness X70 submarine pipeline steel is carried out.The correlation between composition,rolling process and cooling process and drop-weight tear performance is studied.(6)The composition and production process of the X70 submarine pipeline steel are optimized.And it found that the thick-walled deep-sea pipeline steel rolling technology which adapts to the capacity of the production line equipment.