9%Ni steel is a special steel for LNG storage tanks. Phosphorus is a key control element in steel, which has a great influence on the toughness and properties of steel. This steel grade requires that the phosphorus content in steel should not exceed 0.003%. In the aspect of phosphorus control, the original technology of TISCO stainless steel is converter duplex dephosphorization technology, which can control the phosphorus content in steel below 0.003%, but there are some problems such as difficult production organization and high production cost. At the ultra-low temperature of-196℃, this steel is superior to austenitic stainless steel in low temperature toughness and yield strength, and has good cold workability, weldability and crack propagation resistance, so it is an ideal material for manufacturing LNG storage tanks.

9 Nickel steel material has small shrinkage at low temperature, small volume change and good toughness at low temperature.

But in terms of cost, 9 nickel steel is much more expensive than 304.

At present, there are two main standards in the field of LNG onshore design, installation, production, storage and transportation-American standard NFPA 59a-LNG production, storage and treatment standard and EU standard EN1473-LNG installation and equipment-offshore device design.

China has GB/T 20368-20 12 "Production, Storage and Shipping of Liquefied Natural Gas". The American standard NFPA 59A:2009 was revised by redrawing method, and its contents are basically consistent with GB/T 20368 and NFPA 59A.

American standard NFPA59A and EU standard EN 1473 have the same main objects and research contents, but the biggest difference lies in the different ways and methods of determining safety objectives and measures.

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