Seawater corrosion-resistant marine engineering steel and preparation method thereof

A seawater corrosion-resistant marine engineering steel, comprising the following chemical compositions in percentage by mass:

• C:
• 0.011-0.069%, Si:
• 0.11-0.29%, Cr:
• 1.51-1.99%, Nb:
• 0.02-0.05%, Zr:
• 0.01-0.02%, RE:
• 0.0034-0.02%, and a balance of Fe and inevitable impurities;
• wherein mass percentages of Zr element and RE element further satisfy the following formulas:
• 0.01%<Zr+RE<0.02% and Zr/RE=1-3,
• wherein a saturation current density of the seawater corrosion-resistant marine engineering steel is less than or equal to 6.0 mA under a condition that a static electrode potential is equal to −300 mV;
• and a corrosion rate of the seawater corrosion-resistant marine engineering steel is less than or equal to 0.04/mm a under a condition that a mass content of NaCl in a seawater solution is 3.5%.

A method for preparing a seawater corrosion-resistant marine engineering steel, the seawater corrosion-resistant marine engineering steel comprising the following chemical compositions in percentage by mass:

• C:
• 0.011-0.069%, Si:
• 0.11-0.29%, Cr:
• 1.51-1.99%, Nb:
• 0.02-0.05%, Zr:
• 0.01-0.02%, RE:
• 0.0034-0.02%, and a balance of Fe and inevitable impurities;
• wherein mass percentages of Zr element and RE element further satisfy the following formulas:
• 0.01%<Zr+RE<0.02% and Zr/RE=1-3, the method comprising following steps:
• 1) smelting and refining molten steel in turn, carrying out vacuum treatment, and continuously casting the molten steel into a slab to obtain a casting slab;
• 2) Heating and soaking the casting slab to obtain a heat-treated casting slab;
• and
• 3) Continuously rolling the heat-treated casting slab, controlling a final rolling temperature to 750-850° C., cooling by water to 410-550° C. after rolling, and naturally cooling to a room temperature to obtain the seawater corrosion-resistant marine engineering steel.