Wire rod having excellent low temperature impact toughness and manufacturing method therefor
Disclosed are a steel wire rod having excellent low temperature impact toughness and a manufacturing method therefor. The steel wire rod having excellent low temperature impact toughness according to an embodiment of the present invention contains, by weight %, carbon (C): 0.40-0.90%, silicon (Si): 0.5-1.0%, manganese (Mn): 11-25%, copper (Cu): 1.0-3.0%, phosphorus (P): 0.020% or less, sulfur (S): 0.020% or less, aluminum (Al): 0.010-0.050%, nitrogen (N): 0.0010-0.0050%, and the remainder being Fe and unavoidable impurities. The steel wire rod has a microstructure which contains an austenite phase having an area fraction of 95% or more, and a volume fraction of a deformation twin formed in an austenite grain is 1-8%. Therefore, it is possible to provide a steel wire rod having excellent low temperature impact toughness used in industrial machines or automobile parts, etc.
1. A wire rod comprising:
by wt %, carbon (C): 0.40% to 0.90%, silicon (Si): 0.5% to 1.0%, manganese (Mn): 11% to 25%, copper (Cu): 1.0% to 3.0%, phosphorus (P): 0.020% or less, sulfur (S): 0.020% or less, aluminum (Al): 0.010% to 0.050%, nitrogen (N): 0.0010% to 0.0050%, iron (Fe) as a residual component thereof, and inevitable impurities, contents of C and Mn satisfying Relational Expression 1:
9<C×Mn<11,
where C and Mn are contents by wt % of each element,
wherein a microstructure includes an austenite phase in an area fraction of 95% or greater, and a deformation twin formed in an austenite grain is within a range of 1% to 8% in a volume fraction.
2. The wire rod of claim 1 , wherein a size of the austenite grain is 30 μm or less.
3. The wire rod of claim 1 , wherein a thickness of the deformation twin is 15 nm to 35 nm.
4. The wire rod of claim 1 , wherein lamellar spacing of the deformation twin is 40 nm to 100 nm.
5. The wire rod of claim 1 , further comprising a<111> or a<100> fiber texture.
6. A method of manufacturing the wire rod according to claim 1 , comprising:
providing a steel material including, by wt %, carbon (C): 0.40% to 0.90%, silicon (Si): 0.5% to 1.0%, manganese (Mn): 11% to 25%, copper (Cu): 1.0% to 3.0%, phosphorus (P): 0.020% or less, sulfur
(S): 0.020% or less, aluminum (Al): 0.010% to 0.050%, nitrogen (N): 0.0010% to 0.0050%, iron (Fe) as a residual component thereof, and inevitable impurities, in which contents of C and Mn satisfy Relational Expression 1:
9<C×Mn<11,
where C and Mn are contents by wt % of each element;
reheating the steel material;
hot rolling the steel material;
cooling the steel material; and
cold drawing the steel material at an area reduction rate of 10% to 30%.
7. The method of claim 6 , wherein the reheating is performed at a temperature of 950° C. to 1050° C.
8. The method of claim 6 , wherein, in the hot rolling, finish hot rolling is performed at a temperature of 750° C. to 850° C.
9. The method of claim 6 , wherein the cooling is performed at speed of 1° C./s to 5° C./s.