9Ni steel design and application details

9Ni steel chemical composition requirements should be strict, such as Si mass fraction is 0.15% ~ 0.30%, Ni mass fraction is 8.50% ~ 9.50%. Generally speaking, the maximum value of P and S allowed by the standard is about 10 times the actual value of 9Ni steel plate, that is to say: ① When 9Ni steel is used in the design condition of -196℃, the content of P and S must be greatly reduced; ② It is required to reduce the content of P and S as much as possible to ensure that the equipment of 9Ni steel can meet the requirements of the design temperature of -196℃.

The key alloy components artificially added and controlled in the chemical composition design of 9Ni steel are Ni and Mn, which tend to obtain larger values when the control method permits. The composition of other residual alloys should be strictly controlled. Among Ni-based ultra-low temperature steels, 9Ni steel is one of the most difficult steels to develop. 9Ni steel is used in the ultra-low temperature environment of -196 degrees Celsius. It is currently recognized in the industry as one of the steel types with the highest technical content and the most difficult development and production. 9Ni steel is widely used in key parts of cryogenic pressure vessels such as cryogenic transport tankers and LNG storage tanks.