Austenitic steel material having excellent abrasion resistance and toughness and manufacturing method the same
Provided according to one preferred aspect of the present invention are austenitic steel material having superb abrasion resistance and toughness, and a method for producing the austenite steel material. The austenitic steel material having superb abrasion resistance and toughness according to one preferred aspect of the present invention comprises, in wt %, 0.6-1.9% carbon (C); 12-22% manganese (Mn); 5% or lower (excluding 0%) chromium (Cr); 5% or lower (excluding 0%) copper (Cu); 0.5% or lower (excluding 0%) aluminum (Al); 1.0% or lower (excluding 0%) silicon (Si); 0.1% or lower (including 0%) phosphorous (P); 0.02% or lower (including 0%) sulfur (S); and the rest in Fe and unavoidable impurities, and has the microstructure comprising, by surface area fraction, 97% or higher (including 100%) austenite and 3% or lower (including 0%) carbide.
1. A method of manufacturing an austenitic steel sheet, comprising:
preparing a slab comprising, by wt %, 0.6 to 1.9% of carbon, 12 to 22% of manganese, 5% or less of chromium, excluding 0%, 5% or less of copper, excluding 0%, 0.5% or less of aluminum, excluding 0%, 1.0% or less of silicon, excluding 0%, 0.1% or less of phosphorous, including 0%, 0.02% or less of sulfur, including 0%, and a balance of Fe and inevitable impurities;
reheating the slab at 1050° C. or higher;
obtaining a hot-rolled steel sheet by hot-rolling the reheated slab at a finish rolling temperature of 800° C. or higher; and
performing a heat treatment in which the hot-rolled steel sheet is maintained for a maintaining time, in minutes, satisfying Relational Expression 2, at a heat treatment temperature, T, satisfying Relational Expression 1 below, and the hot-rolled steel sheet is water-cooled to 500° C. or lower at a cooling speed of 15° C./sec or higher,
wherein the steel sheet has a microstructure comprising, by an area fraction, austenite of 97% or higher, including 100%, and carbides of 3% or lower, including 0%, and
wherein the steel sheet has a wear amount of 2.0 g or less and an impact toughness of 100 J or higher,
530+285[C]+44[Cr]<T<1446−174[C]−3.9[Mn] [Relational Expression 1]
where T is a heat treatment temperature, in ° C., and [C], [Cr] and [Mn] each indicate wt % of each element,
t+ 10<maintaining time< t+ 30 [Relational Expression 2]
where t is a thickness of the hot-rolled steel sheet in mm.
2. The method of claim 1 , wherein a temperature of the reheating the slab is 1050 to 1250° C.
3. The method of claim 1 , wherein the finish rolling temperature of the hot-rolling is 800° C. or higher and a non-recrystallization temperature, Tnr, or lower.
4. The method of claim 1 , wherein the thickness of the hot-rolled steel sheet is 4 to 50 mm.
5. The method of claim 1 , wherein a grain size of austenite is 500 μm or less.
6. The method of claim 1 , wherein the steel sheet has a wear amount of less than 2.0 g and an impact toughness of higher than 100 J.