Abstract: Disclosed is a method for manufacturing a 5Ni steel plate with a low remanence and an excellent surface quality to be used in a ship. The process flow thereof comprises: converter smelting?LF refining?RH high vacuum degassing?treatment with Ca?continuous casting?a slow cooling treatment to the slab?cleaning the surface of the slab?heating?rolling?quenching twice?tempering. The constituents comprise a low content of carbon, a low content of silicon, and 5% Ni, with V and Nb being added thereto, which improves the hardenability, improves the toughness at a low temperature, and improves the starting temperature of non-recrystallization of austenite. The steel plate can be subjected to high-temperature rolling and high-temperature quenching so as to significantly improve the shape of the plate, thus being applicable to the production of thin products.

Abstract: Disclosed is a method for manufacturing a 5Ni steel plate with a low remanence and an excellent surface quality to be used in a ship. The process flow thereof comprises: converter smelting->LF refining->RH high vacuum degassing->treatment with Ca->continuous casting->a slow cooling treatment to the slab->cleaning the surface of the slab->heating->rolling->quenching twice->tempering. The constituents comprise a low content of carbon, a low content of silicon, and 5% Ni, with V and Nb being added thereto, which improves the hardenability, improves the toughness at a low temperature, and improves the starting temperature of non-recrystallization of austenite. The steel plate can be subjected to high-temperature rolling and high-temperature quenching so as to significantly improve the shape of the plate, thus being applicable to the production of thin products.

Abstract: The invention relates to a 9Ni steel plate for ship LNG storage tank with high strength and low yield ratio. According to the mass percentage, the chemical constituents are C: 0.02-0.05%, Si: 0.10-0.30%, Mn: 0.50-0.80%, Ni: 8.90-9.50%, P: ?0.0070%, s: ?0.0020%, Cr: 0.10-0.25%, Alt: 0.010-0.035%, Nb: 0.010-0.020%, Ca: 0.0005-0.0030%, O: ?0.0012%, N: ?0.004%, H: ?0.00015%, and the balance is Fe and unavoidable impurity elements. The production process flow is: smelting in a converter or electric furnace->RH vacuum degassing->LF refining->RH high vacuum degassing->Ca Treatment->continuous casting->slab slow cooling treatment->slab surface cleaning->heating->rolling ->quenching->tempering. For the 9Ni steel, especially the 9Ni thin steel plate, the invention adopts the constituents design of low C, 9% Ni, addition of Nb and Cr.