Austenitic steel material having excellent hot workability and manufacturing method therefor
Provided according to one embodiment of the present invention are a non-magnetic steel material and a method for manufacturing the same. The steel material comprises 15-27 wt % of manganese, 0.1-1.1 wt % of carbon, 0.05-0.50 wt % of silicon, 0.03 wt % or less (0% exclusive) of phosphorus, 0.01 wt % or less (0% exclusive) of sulfur, 0.050 wt % or less (0% exclusive) of aluminum, 5 wt % or less (0% inclusive) of chromium, 0.01 wt % or less (0% inclusive) of boron, 0.1 wt % or less (0% exclusive) of nitrogen, and a balance amount of Fe and inevitable impurities, has an index of sensitivity of 3.4 or less, the index of sensitivity being represented by the following relational expression (1): [Relational expression 1]−0.451+34.131*P+111.152*Al−799.483*B+0.526*Cr≤3.4 (wherein [P], [Al], [B] and [Cr] each mean a wt % of corresponding elements), and contains a microstructure with austenite at an area fraction of 95% or greater therein.
1. An austenitic steel material, the austenitic steel material comprising manganese (Mn): 15 wt % to 27 wt %, carbon (C): 0.1 wt % to 1.1 wt %, phosphorus (P): more than 0 wt % and 0.03 wt % or less, aluminum (Al): 0.021 wt % to 0.050 wt %, chromium (Cr): 2.03 wt % to 5 wt %, boron (B): 0.01 wt % or less, and a balance of iron (Fe) and inevitable impurities, wherein the austenitic steel material has a composition index of sensitivity expressed by Formula 1 below within a range of 3.4 or less,
−0.451+34.131*P+111.152*Al−799.483*B+0.526*Cr≤3.4 [Formula 1]
where each of [P], [Al], [B], and [Cr] is a weight percent (wt %) of a corresponding element,
wherein the austenitic steel material has a microstructure comprising austenite in an area fraction of 95% or greater, and
wherein the austenite has an average grain size of 26 to 60 μm.
2. The austenitic steel material of claim 1 , wherein the austenitic steel material further comprises silicon (Si): 0.05 wt % to 0.50 wt %, sulfur (S): more than 0 wt % and 0.01 wt % or less, nitrogen (N): more than 0 wt % and 0.1 wt % or less.
3. The austenitic steel material of claim 1 , wherein the austenitic steel material comprises nitrogen (N) in a range of 0.001 wt % to 0.06 wt %.
4. The austenitic steel material of claim 1 , wherein the austenitic steel material comprises nitrogen (N) in a range of 0.005 wt % to 0.03 wt %.
5. The austenitic steel material of claim 1 , wherein the austenitic steel material comprises chromium (Cr) in a range of 2.03 wt % to 4 wt %.
6. The austenitic steel material of claim 1 , wherein the austenitic steel material comprises 0.0005 wt % or greater of boron (B).
7. The austenitic steel material of claim 1 , wherein the austenitic steel material comprises 15 wt % to 25 wt % of manganese (Mn).
8. The austenitic steel material of claim 1 , wherein the austenitic steel material comprises 17 wt % to 25 wt % of manganese (Mn).
9. The austenitic steel material of claim 1 , wherein the austenitic steel material comprises 19.6 wt % to 25 wt % of manganese (Mn).
10. The austenitic steel material of claim 1 , wherein the austenitic steel material comprises 0.1 wt % to 1.0 wt % of carbon (C).
11. The austenitic steel material of claim 1 , wherein the austenitic steel material comprises 0.1 wt % to 0.8 wt % of carbon (C).
12. The austenitic steel material of claim 1 , wherein the austenitic steel material comprises 0.05 wt % to 0.29 wt % of silicon (Si).