High nitrogen steel with high strength, low yield ratio and high corrosion resistance for ocean engineering and preparation method therefor

A preparation method for high nitrogen steel for ocean engineering, wherein the high nitrogen steel for ocean engineering comprises the following chemical components by weight percentage:

• C≤0.01%, Si≤0.1%, Cr 17%-19%, Mn 14%-16%, Mo 1%-1.5%, Ti≤0.05%, N 0.45%-0.6%, P<0.01%, S≤0.01%, O≤0.02%, and a balance of iron;
• the preparation method comprising the following steps:
• S1 raw material weighing:
• calculating and weighing raw materials including industrial pure iron, low carbon ferrochromium, electrolytic manganese, ferromolybdenum, chromium nitride, nitrogenized manganese, aluminum and titanium for later use;
• S2 ingot preparation, remelting and smelting:
• melting, casting and cooling the above raw materials to form an ingot, and carrying out electroslag remelting and smelting of the ingot under nitrogen protection, thus obtaining an electroslag ingot;
• S3 solution and forging treatments:
• carrying out solution treatment of the electroslag ingot at 1000° C.-1050° C. for 20 h-24 h and then cooling the electroslag ingot using water;
• carrying out forging treatment with an initial forging temperature of not less than 1050° C. and a final forging temperature of not less than 900° C. during forging;
• after forging, cooling the electroslag ingot to room temperature using air, thus obtaining a square billet;
• and
• S4 hot rolling and post-rolling treatment:
• placing the square billet in a heating furnace, soaking at 1050° C. for 2 h, and raising the temperature to 1100° C. within 0.5 h;
• starting hot rolling at 1000-1100° C., and finishing the hot rolling at 890-930° C.;
• after rolling, cooling the square billet to room temperature using air or water, thus obtaining the high nitrogen steel for ocean engineering.