Ultra-high strength cold-rolled steel sheet with corrosion resistance and manufacturing method therefor

A method of manufacturing an ultra-high-strength cold-rolled steel plate with corrosion resistance, the method comprising:

• manufacturing a hot-rolled steel plate by hot-rolling a steel comprising:
• in % by weight, carbon (C):
• 0.1% to 0.5%, silicon (Si):
• 0.01% to 2.0%, manganese (Mn):
• 0.1% to 5.0%, aluminum (Al):
• 0.01% to 2.0%, chromium (Cr):
• greater than 0% and 3.0% or less, molybdenum (Mo):
• greater than 0% and 1.0% or less, nickel (Ni):
• 0.02% to 3.0%, copper (Cu):
• 0.02% to 3.0%, titanium (Ti):
• 0.01% to 0.2%, niobium (Nb):
• 0.01% to 0.1%, vanadium (V):
• 0.01% to 1.0%, boron (B):
• 0.001% to 0.005%, phosphorus (P):
• greater than 0% and 0.02% or less, sulfur (S):
• greater than 0% and 0.01% or less, and a remainder containing iron (Fe) and other inevitable impurities, in which a ratio ([Cu]/[Ni]) of a content of the copper (Cu) to a content of the nickel (Ni) ranges from 0.54 to 5.7;
• manufacturing a cold-rolled steel plate by cold-rolling the hot-rolled steel plate;
• annealing the cold-rolled steel plate by maintaining it at 800° C. to 900° C. for 60 seconds to 600 seconds;
• first cooling the annealed cold-rolled steel plate to 500° C. to 700° C. at a cooling rate of 1° C./sec to 20° C./sec;
• second cooling the first cooled cold-rolled steel plate to a temperature of less than Mf at a cooling rate of 5° C./sec to 100° C./sec;
• and
• tempering the cold-rolled steel plate, which has been subjected to the second cooling, at 100° C. to 350° C.

A method of manufacturing an ultra-high-strength cold-rolled steel plate with corrosion resistance, the method comprising:

• hot-rolling a steel composition to provide a hot-rolled steel plate, wherein the steel composition comprises:
• in % by weight, carbon (C):
• 0.1% to 0.5%, silicon (Si):
• 0.01% to 2.0%, manganese (Mn):
• 0.1% to 5.0%, aluminum (Al):
• 0.01% to 2.0%, chromium (Cr):
• greater than 0% and 3.0% or less, molybdenum (Mo):
• greater than 0% and 1.0% or less, nickel (Ni):
• 0.02% to 3.0%, copper (Cu):
• 0.02% to 3.0%, titanium (Ti):
• 0.01% to 0.2%, niobium (Nb):
• 0.01% to 0.1%, vanadium (V):
• 0.01% to 1.0%, boron (B):
• 0.001% to 0.005%, phosphorus (P):
• greater than 0% and 0.02% or less, sulfur (S):
• greater than 0% and 0.01% or less, and a remainder containing iron (Fe) and other inevitable impurities, in which a ratio ([Cu]/[Ni]) of a content of the copper (Cu) to a content of the nickel (Ni) ranges from 0.54 to 5.7;
• cold-rolling the hot-rolled steel plate to provide a cold-rolled steel plate;
• annealing the cold-rolled steel plate by maintaining it at 800° C. to 900° C. for 60 seconds to 600 seconds;
• first cooling the annealed cold-rolled steel plate to 500° C. to 700° C. at a cooling rate of 1° C./sec to 20° C./sec;
• second cooling the first cooled cold-rolled steel plate to 400° C. to 500° C. at a cooling rate of 5° C./sec to 100° C./sec;
• molten zinc-plating the second cooled cold-rolled steel plate;
• and
• tempering the molten zinc-plated cold-rolled steel plate at 100° C. to 350° C.