Austenitic light-weight high-strength steel with excellent properties of welds, and method of manufacturing the same

1. A method of manufacturing an austenitic steel, the method comprising:

hot-rolling a steel including 20 wt % to 30 wt % of manganese (Mn), 6 wt % to 12 wt % of aluminum (Al), 0.6 wt % to 1.5 wt % of carbon (C), 0.3 wt % to 0.95 wt % of vanadium (V), and a remaining amount of iron (Fe) and other unavoidable impurities;

homogenizing the hot-rolled steel; and

aging the homogenized steel,

wherein hot-rolling the steel comprises:

hot-rolling the steel under a finish rolling temperature ranging from 900° C. to 1000° C.; and

cooling the steel to 600° C. or less, wherein cooling the steel comprises cooling the steel at an average cooling rate ranging from 10° C./sec to 50° C./sec, and

wherein aging the homogenized steel comprises:

aging the homogenized steel at a temperature ranging from 540° C. to 560° C. for 10 minutes or more; and

cooling the steel to a temperature of 200° C. or less, at an average cooling rate of 10° C./sec or less.

2. The method of claim 1 , wherein the steel further includes 0.02 wt % to 0.06 wt % of niobium (Nb).

3. The method of claim 2 , wherein a total amount of niobium and vanadium is 0.35 wt % to 0.95 wt %.

4. The method of claim 1 , wherein homogenizing the hot-rolled steel comprises:

homogenizing the hot-rolled steel at a temperature ranging from 1000° C. to 1200° C. for a time ranging from 1 to 3 hours; and

cooling the steel to a temperature of 600° C. or less, at an average cooling rate of 10° C./sec or more.