High hardness wear-resistant steel having excellent low-temperature impact toughness, and manufacturing method therefor

Abstract

The present invention provides wear-resistant steel which has high hardness while having wear resistance and high impact toughness at low temperature, and a manufacturing method therefor.

1 . A high hardness wear-resistant steel comprising, by weight: 0.25 to 0.50% of carbon (C), 1.0 to 1.6% of silicon (Si), 0.6 to 1.6% of manganese (Mn), 0.05% or less (excluding 0%) of phosphorus (P), 0.02% or less (excluding 0%) of sulfur (S), 0.07% or less (excluding 0%) of aluminum (Al), 0.5 to 1.5% of chromium (Cr), 0.0005 to 0.004% of calcium (Ca), and 0.006% or less of nitrogen (N), with a balance of Fe and other unavoidable impurities,
 wherein the wear-resistant steel includes a martensite and bainite composite structure as a microstructure and a retained austenite phase in an area fraction of 2.5 to 10%.   
     
     
         2 . The high hardness wear-resistant steel of  claim 1 , further comprising, by weight: one or more of 0.01 to 0.5% of nickel (Ni), 0.01 to 0.3% of molybdenum (Mo), 0.005 to 0.025% of titanium (Ti), 0.0002 to 0.005% of boron (B), and 0.2% or less of vanadium (V). 
     
     
         3 . The high hardness wear-resistant steel of  claim 1 , wherein the martensite and bainite composite structure has an average lath size of 0.3 μm or less. 
     
     
         4 . The high hardness wear-resistant steel of  claim 1 , wherein the wear-resistant steel includes the martensite and bainite composite structure at an average fraction of 90% or more. 
     
     
         5 . The high hardness wear-resistant steel of  claim 1 , wherein the wear-resistant steel has a surface hardness of 460 to 540 HB and an impact absorption energy −40° C. of 17 J or more. 
     
     
         6 . The high hardness wear-resistant steel of  claim 1 , wherein the wear-resistant steel has a thickness of 5 to 40 mm. 
     
     
         7 . A manufacturing method for a high hardness wear-resistant steel, the method comprising:
 preparing a steel slab including, by weight: 0.25 to 0.50% of carbon (C), 1.0 to 1.6% of silicon (Si), 0.6 to 1.6% of manganese (Mn), 0.05% or less (excluding 0%) of phosphorus (P), 0.02% or less (excluding 0%) of sulfur (S), 0.07% or less (excluding 0%) of aluminum (Al), 0.5 to 1.5% of chromium (Cr), 0.0005 to 0.004% of calcium (Ca), and 0.006% or less of nitrogen (N), with a balance of Fe and other unavoidable impurities;   heating the steel slab in a temperature range of 1050 to 1250° C.;   rough rolling the heated steel slab in a temperature range of 950 to 1150° C.;   after the rough rolling, performing finish hot rolling in a temperature range of 850 to 950° C. to manufacture a hot rolled steel sheet; and   cooling the hot rolled steel sheet to 200 to 400° C. at a cooling rate of 25° C./s or more and then performing air cooling.   
     
     
         8 . The manufacturing method for a high hardness wear-resistant steel of  claim 7 , wherein the steel slab further includes, by weight: one or more of 0.01 to 0.5% of nickel (Ni), 0.01 to 0.3% of molybdenum (Mo), 0.005 to 0.025% of titanium (Ti), 0.0002 to 0.005% of boron (B), and 0.2% or less of vanadium (V). 
     
     
         9 . The manufacturing method for a high hardness wear-resistant steel of  claim 7 , wherein self-tempering occurs during the air cooling. 
     
     
         10 . The manufacturing method for a high hardness wear-resistant steel of  claim 7 , wherein the air cooling is performed down to 150° C. or lower.